Patent Application
20230268714
This application relates generally to single-mode lasers.
Lasers are widely used in telecommunications, sensing, and test and measurement applications. Many high-power lasers are not single-mode while many single-mode lasers do not provide high optical powers.
High-power single-mode lasers that are capable of providing high optical power and single mode operation can be useful for many applications. Example embodiments described herein have several features, no single one of which is indispensable or solely responsible for their desirable attributes. Without limiting the scope of the claims, some of the advantageous features will now be summarized.
Certain embodiments provide a laser comprising a waveguide configured to support a vertically confined fundamental optical mode and at least one vertically confined higher order optical mode. The laser further comprises an active region at a first position with respect to the waveguide. The laser further comprises a grating (also referred to as grating layer) at a second position with respect to the waveguide. The first position of the active region and the second position of the grating are configured to reduce a first lasing threshold for the fundamental optical mode and to increase a second lasing threshold for the at least one higher order optical mode.
Certain embodiments provide a method for designing a laser comprising a waveguide, an active region, and a grating. The method comprises providing a position of the active region and a position of the grating. The method further comprises calculating at least a vertically confined first optical mode and at least one vertically confined second optical mode supported by the waveguide for the position of the active region and the position of the grating. The method further comprises adjusting the positions of the active region and the grating such that a first product of an overlap of the first optical mode with the grating and an overlap of the first optical mode with the active region is greater than a second product of an overlap of the at least one second optical mode with the grating and an overlap of the at least one second optical mode with the active region. The method further comprises re-calculating at least the first optical mode and the at least one second optical mode and determining perturbations of at least the first optical mode and the at least one second optical mode resulting from the adjusted positions of the active region and the grating. The method further comprises calculating a difference between the first product and the second product. The method further comprises adjusting, if the difference is less than a threshold value, the positions of the active region and the grating such that the first product is larger than the second product.
Certain embodiments provide a laser comprising a waveguide configured to support a vertical fundamental optical mode and at least one vertically confined higher order optical mode, an active region at a first position with respect to the waveguide, a grating at a second position with respect to the waveguide. At least one of the first position or the second position overlaps with a null of at least one higher order mode.
Certain embodiments provide a laser comprising a waveguide layer configured to support a fundamental vertical optical mode and at least a first higher order vertical optical mode, a first active region at a first position with respect to the waveguide layer, a second active region at a second position with respect to the waveguide layer. The laser further comprises a tunnel junction between the first and the second positions, and a grating at a third position with respect to the waveguide layer. The first and the second positions of the first and the second active regions, and the third position of the grating configured to make a first lasing threshold for the fundamental vertical optical mode smaller than a second lasing threshold for the first higher order vertical optical mode.
Certain embodiments provide a method for designing a laser comprising a waveguide layer, at least two active regions, and a grating. The method comprises providing a first position of a first active region, a second position of a second active region, a third position of the grating; calculating at least a vertically confined first vertical optical mode and at least one vertically confined second vertical optical mode supported by the waveguide layer for the first and the second positions of the first and second active regions and the third position of the grating. The method further comprises adjusting the positions of the active regions and the grating such that a first product of an overlap of the first vertical optical mode with the grating and an overlap of the first vertical optical mode with the first and the second active regions is greater than a second product of an overlap of the at least one second vertical optical mode with the grating and an overlap of the at least one second vertical optical mode with the first and the second active regions. The method further comprises re-calculating at least the first vertical optical mode and the at least one second vertical optical mode and determining perturbations of at least the first vertical optical mode and the at least one second vertical optical mode resulting from the adjusted positions of the first and the second active regions and the grating; calculating a difference between the first product and the second product adjusting, if the difference is less than a threshold value, the positions of the first and the second active regions and the grating such that the first product is larger than the second product.
Certain embodiments provide a laser comprising a waveguide layer configured to support a first vertical optical mode and at least a second vertically confined vertical optical mode, a first active region at a first position with respect to the waveguide layer, a second active region at a second position with respect to the waveguide layer, a tunnel junction below the first position and above the second position and a grating at a third position with respect to the waveguide layer. A first product of an overlap of the first vertical optical mode with the grating and an overlap of the first vertical optical mode with the first and the second active regions is greater than a second product of an overlap of the second vertical optical mode with the grating and an overlap of the second vertical optical mode with the first and the second active regions.
Certain embodiments provide a laser comprising a waveguide layer configured to support a first vertical optical mode and at least a second vertically confined vertical optical mode, a first active region at a first position with respect to the waveguide layer, a second active region at a second position with respect to the waveguide layer, a third active region at a third position with respect to the waveguide layer, a first tunnel junction below the first position and above the second position, a second tunnel junction below the second position and above the third position, and a grating at a fourth position with respect to the waveguide layer. A first product of an overlap of the first vertical optical mode with the grating and an overlap of the first vertical optical mode with the first, second, and the third active regions is greater than a second product of an overlap of the second vertical optical mode with the grating and an overlap of the second vertical optical mode with the first, second, and the third active regions.
Certain embodiments provide a laser comprising a waveguide layer configured to supports at least a fundamental vertical optical mode, a ridge layer above the waveguide layer, a high index layer between the waveguide layer and the ridge layer, the high index layer having a refractive index larger than a refractive index of the ridge layer and a refractive index of the waveguide layer, and at least two active regions within the waveguide layer, the active regions configured to provide optical gain the fundamental vertical optical mode.
In the following description of the various embodiments, reference is made to the accompanying drawings which form a part hereof, and which show, by way of illustration, various embodiments described herein. Other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.
These and other features will now be described with reference to the drawings summarized above. The drawings and the associated descriptions are provided to illustrate embodiments and not to limit the scope of the disclosure or claims. Throughout the drawings, reference numbers may be reused to indicate correspondence between referenced elements.
Although certain example embodiments are disclosed below, inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses and to modifications and equivalents thereof. Thus, the scope of the claims appended hereto is not limited by any of the particular embodiments described below. For example, in any method or process disclosed herein, the acts or operations of the method or process can be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding certain embodiments; however, the order of description should not be construed to imply that these operations are order dependent. Additionally, the structures, systems, and/or devices described herein can be embodied using a variety of techniques including techniques that may not be described herein but are known to a person having ordinary skill in the art. For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not necessarily all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments can be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may also be taught or suggested herein. It will be understood that when an element or component is referred to herein as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements can be present therebetween. For clarity of description, “reflector” or “mirror” can be used interchangeably to refer to an optical element and/or a surface having a reflectivity greater than or equal to about 0.01% and less than or equal to 100%. For example, an optical element and/or a surface having a reflectivity greater than or equal to about 5% and less than or equal to 99%, greater than or equal to about 10% and less than or equal to 90%, greater than or equal to about 15% and less than or equal to 80%, greater than or equal to about 20% and less than or equal to 70%, greater than or equal to about 30% and less than or equal to 60%, or any value in any range/sub-range defined by these values can be considered as a reflector or mirror.
Semiconductor lasers are widely used in many applications ranging from telecommunications to sensing, medical applications, and optical pumping (e.g., pumping other laser mediums or amplifier mediums). Semiconductor lasers can comprise a substrate including an optically active layer thereon. In some implementations, the optically active layer can be configured as an epitaxial layer grown over the substrate using semiconductor growth technology. For many applications, it can be advantageous for these semiconductor lasers to output a single longitudinal mode. One method for achieving single longitudinal mode lasing in III-V semiconductor lasers is by incorporation of a Bragg grating, to create either a Distributed Feed Back (DFB) Semiconductor Laser or a Distributed Bragg Reflector (DBR) Laser. Many embodiments of DBR or DFB laser devices can be configured as edge emitting laser devices that are configured to output light from an edge of the laser device. The plane including the edge can be generally oriented along a direction normal to the substrate of the DBR or DFB laser device. The light output from certain embodiments of the edge emitting DBR and DFB laser devices can be coupled to fibers or other passive waveguide circuits. However, the optical mode output from various embodiments of DFB or DBR lasers can be small and/or asymmetrical and may not be matched with the size and/or shape of optical fibers or waveguides of other passive waveguide circuits into which the light from the DBR or DFB laser device is to be coupled. Accordingly, certain embodiments described herein advantageously provide edge emitting laser devices that are configured to output a single spatial mode having a large size that is matched with the size and/or shape of optical fibers or waveguides of other passive waveguide circuits into which the light from these laser devices is to be coupled.
Certain embodiments described herein provide edge emitting semiconductor laser devices that comprise mode converters that are configured to convert the mode of the light output from the edge emitting semiconductor laser devices to larger and/or a more symmetric shape that can be easily coupled into a glass optical fiber, a plastic optical fibers, a polymer waveguide, a doped glass waveguide, a silicon waveguide, and/or a silicon nitride waveguide. In certain such embodiments, the mode converters can advantageously provide a low loss optical connection between the laser and other optical components.
Without relying on any particular theory, the near field optical mode size, in many implementations of semiconductor lasers comprising a III-V material can be small and elliptical. In many implementations, the full width of the elliptical mode along the minor axis (e.g., the distance along the minor axis between positions at which the intensity is 1/e2 of the maximum intensity of the elliptical mode) can be approximately less than or equal to 1 micron and the full width of the elliptical mode along the major axis (e.g., the distance along the major axis between positions at which the intensity is 1/e2 of the maximum intensity of the elliptical mode) can be less than or equal to 5 microns. The minor axis of the elliptical mode can be oriented parallel to the crystal growth direction. This type of elliptical mode profile that is compressed along a direction parallel to the crystal growth direction may not be compatible with the size and shape of many implementations of optical fibers and/or doped glass waveguides. For example, many implementations of optical fibers and/or doped glass waveguides can comprise a circular core having a diameter of about 9 microns. Many implementations of SiNx waveguides can be configured to have an elliptical cross-sectional shape such that an optical mode having an elliptical shape mode can be efficiently in-coupled into the waveguide. However, even in such implementations, the small size of the optical mode can make the optical alignment process difficult as even a small misalignment can increase optical losses.
One approach to increase the size of the optical mode includes providing a symmetric buried heterostructure waveguide with a tapered section which allows a large optical mode to be supported by a small, symmetric buried waveguide. The size of the optical mode is adiabatically enlarged over the length of the taper. However, some optical loss can be incurred as the optical mode propagates through the length of the taper over which the optical mode is adiabatically enlarged. This approach is advantageous to increase the size of optical modes that are symmetric but have a size less than or equal to about one micron. Other approaches to increase the size of an optical mode can include waveguide couplers in which the optical mode from the laser is coupled vertically or laterally to an adjacent passive waveguide that can support an optical mode with a large optical size. However, these approaches can introduce absorption and scattering optical losses as the optical mode propagates through the length of the passive waveguide over which the mode transfer occurs.
Another approach to increase the size of the optical mode output from a semiconductor laser includes using large waveguide cores. However, this approach may not be practical for single mode operation because most conventional laser designs on semiconductor materials (e.g., materials from the III-V group) become multimode when the waveguide thickness is increased such that the core of the waveguide is enlarged. A first implementation of a semiconductor laser capable of outputting a large and symmetric optical mode is a slab-coupled optical waveguide laser (SCOWL), which uses a large weak confinement slab waveguide beneath the active region. The size of the near-field optical mode in such structures can be 2 to 3 microns in diameter, or even larger.
In various implementations, the thickness of the waveguide layer 102 can be between about 0.5 micron and about 20 microns. For example, the thickness of the waveguide layer 102 can be greater than 0.5 micron and less than or equal to 2 microns, greater than or equal to 1.5 microns and less than or equal to 5 microns, greater than or equal to 4 microns and less than or equal to 8 microns, greater than or equal to 7.5 microns and less than or equal to 10 microns, greater than or equal to 9.0 microns and less than or equal to 15 microns. greater than or equal to 12.5 microns and less than or equal to 20 microns, or any value in any range and/or sub-range defined by these values.
In various implementations, the cladding region 103 can comprise semiconductor materials such as, for example, InP, AlGaAs, InGaP, or combinations thereof. The waveguide layer 102 can comprise semiconductor materials such as, for example, InGaAsP, AlInGaAs, AlGaAs or combinations thereof. In implementations in which the cladding region 103 and the waveguide layer 102 comprise AlGaAs, the doping concentration of AlGaAs in the waveguide layer 102 can be different from the doping concentration of AlGaAs in the cladding region 103. The ridge 100 can comprise semiconductor materials such as, for example, InP, AlGaAs having a same doping concentration as the AlGaAs of the cladding region 103, InGaP, or combinations thereof.
In various implementations of the SCOWL, as schematically illustrated by
A second implementation of a semiconductor laser capable of outputting a large and symmetric optical mode is a super-large optical cavity (SLOC) laser, an example of which is schematically illustrated in
Certain embodiments described herein utilize laser designs and/or architectures that comprise a waveguide layer having an enlarged thickness (e.g., similar to the SCOWL and SLOC laser architectures described above) and further comprising a grating (e.g., grating layer; grating structure) in the laser cavity to filter the vertically confined modes of the laser down to fewer vertically confined modes (e.g., to a single vertically confined mode). As used herein, the term “vertically confined mode” has its broadest reasonable meaning, including referring to a mode that is confined in a direction parallel to the growth direction of the semiconductor crystal. In some cases, a vertically confined mode can be a vertical optical mode (also referred to as a transverse optical mode) of a waveguide or waveguide layer. A waveguide or waveguide layer may support one or more vertical optical modes each having a different optical field and optical intensity distribution along a vertical direction. The vertical direction (e.g., along y-axis in
In certain embodiments, the laser comprises a grating layer 106 over the active region 101 in the ridge 100, as schematically illustrated by
In certain embodiments, the grating layer 106 is in the active region 101 (e.g., within the active quantum well region), while in certain other embodiments, the grating layer 106 is in the layered waveguide 105, as schematically illustrated in
In certain embodiments, the grating layer 106 comprises a material having higher or lower refractive index as compared to the material of the waveguide 105 or the cladding region 103. In certain embodiments, as schematically illustrated in
Growing a thick slab waveguide 102 comprising a material that is different from the material of the cladding region 103 over the cladding region 103 can be difficult and can cause defects in the thick slab waveguide 102. In certain embodiments, the layered waveguide 105 (e.g., comprising relatively thinner layers of the waveguide material alternating with thin layers of the cladding material) is simpler to fabricate than a slab waveguide 102. For example, the layered waveguide 105 can comprise relatively thin layers of a waveguide material comprising quaternary or ternary layers or other layers interleaved with relatively thin layers of InP that are grown on a cladding region 103 comprising InP. The grating etch can etch or punch through one or more of the non-InP layers, resulting in a very well controlled coupling coefficient where the thickness of the grating 106 can be controlled only by the thickness of the non-InP layers. Another stack of relatively thin layers of InP interleaved with relatively thin layers of the waveguide material can be further grown over the waveguide layer or layers comprising the grating 106.
In certain embodiments, for lower confinement within the quantum wells and/or placement of the quantum wells closer to one side of the waveguide (e.g., at the top near a p-doped side of the waveguide in a laser grown with n-doping on the bottom), the grating layer 106 is positioned at or near a null or minimum of the second order mode 104b, as schematically illustrated in
In certain embodiments, the grating 106 in a SLOC-like laser architecture provides an additional parameter to suppress higher order modes to ensure single mode lasing. For example, the active region 101 (e.g., comprising quantum wells) can be placed such that the fundamental mode 104a experiences higher gain than do other higher order optical modes (e.g., the second order mode 104b). Tailoring the placement of the grating layer 106 can provide an additional mode selection method to preferentially select the fundamental mode 104a (or, similarly, to deselect other higher order modes).
In certain embodiments, the active region 101 and/or the grating layer 106 is configured (e.g., positioned) to suppress lasing of one or more modes (e.g., all but the fundamental mode 104a or some selected higher order mode). For example, as shown in
The method of designing and/or fabricating a laser by positioning the active region 101 and/or the grating layer 106 to selectively reduce the number of spatial modes supported by the waveguide is not limited to ridge waveguide architectures (e.g., schematically illustrated in
As described herein, designing and/or fabricating the various example lasers comprises the placement of the grating layer 106 and the active region 101. In certain embodiments in which only two vertical modes that are perpendicular to the direction of the material growth are present, the grating layer 106, the active region 101, or both can be positioned at or near a center of the waveguide so as to coincide with a null or a minimum of the second order mode 104b. In certain other embodiments in which three vertical modes are present, the grating layer 106 and/or the active region 101 can be offset from the center of the waveguide so as to coincide with a null or a minimum of two higher order modes (e.g., second order mode 104b; third order mode 104c). During the design phase, the positions of the grating layer 106 and the active region 101 can be calculated using a mathematical model to simulate the modes which are supported by the waveguide, and the positions of the active region 101 and the grating layer 106 can be iteratively changed relative to the peaks and nulls of the fundamental mode 104a and the higher order modes. Without relying on any particular theory, the position of the active region 101 can perturb the mode profile significantly as a result of its thickness and relatively high index of refraction. The grating layer 106, however, provides a small perturbation to the mode profile, and can be moved within the waveguide without significantly altering the nature of the supported modes. In certain embodiments, the iterative process can be advantageous to improve or optimize the position of the active region 101. In certain embodiments, the placement of the grating layer 106 can be calculated initially and does not change much during the iterative process.
In an operational block 1101, the example method of
In certain embodiments, as schematically illustrated by
In certain embodiments, as schematically illustrated by
In certain embodiments, the waveguide 105 of the laser schematically illustrated in
In certain embodiments, a laser (e.g., a semiconductor laser) may include two or more spatially separated active regions or layers that provide optical gain to one or more optical modes (e.g., vertical optical modes) confined in a waveguide layer of the semiconductor laser. In some examples, a laser may comprise multiple active regions within a thick waveguide layer that supports multiple vertical optical modes. In some examples, each active region may comprise one or more quantum wells (or quantum well layers) that can provide optical gain to light associated with different vertical optical modes of the waveguide layer, upon being pumped, e.g., by an electric current (also referred to as injection current). The quantum wells may be configured to provide optical gain within an operational wavelength range of the laser. The laser cavity may support one or more vertical optical modes having wavelengths within the operational wavelength range of the laser. In various embodiments, two different active regions of a laser may comprise different numbers of quantum wells and/or provide different magnitudes of optical gain to a vertical optical mode of the laser. In some cases, the optical gain that an active region provides to a vertical optical mode is proportional to an overlap (e.g., an overlap integral) between the vertical optical mode and the active region. In some cases, two active regions of a laser may be separated by a separation region or layer that does not provide optical gain at least within the operational wavelength range of the laser or a within a wavelength range that can be amplified by the active regions. In some cases, the separation region or layer between the two active regions may comprise a carrier transport region that allows the electrons and/or holes to flow from one of the active regions to the other active region. In some cases, the carrier transport region may comprise a tunnel junction.
As described above, a grating layer (also referred to as grating) may provide optical feedback (e.g., in a longitudinal direction parallel to a direction of propagation of light in the laser cavity) to one or more optical vertical modes of the waveguide layer (e.g., to a corresponding light beam having a vertical field distribution according to the corresponding vertical optical modes). A laser having two or more spatially separated active regions may comprise one more features described above with respect to the lasers having a single active region. For example, the active regions and the grating layer may be positioned within the laser waveguide so as to reduce the lasing threshold for a first vertical mode (e.g., a threshold injection current that can cause the first vertical mode to lase) compared to that of a second vertical mode supported by the waveguide layer of the laser. In some examples, the first vertical mode can be the fundamental vertical mode of the waveguide layer and the second vertical mode can be a high order vertical mode of the waveguide layer (e.g., the first, second, or the third order mode).
In various implementations, the grating layer may coincide with a null or a minimum of the intensity profile of a first high order mode, while one or both gain regions coincide with a null or a minimum of the intensity profile for a second high order mode different from the first high order mode. In some cases, the active regions and the grating layer may be positioned in regions of the waveguide layer that are unfavorable to one or more high order modes while being favorable to the fundamental vertical mode, such that a threshold current required for oscillation of the fundamental vertical mode in the laser cavity is less than those of the higher order modes.
In some cases, the one or more active regions may be arranged to allow an electric current to sequentially pass through the active regions (e.g., along a vertical direction extended from top electrode to a substrate of the laser. In some such cases, at least one tunnel junction (e.g., a pn semiconductor tunnel junction) may be included between at least two active regions (or layers) to enable electric current (e.g., charge carriers) to flow from one of the active regions to another active region (e.g., a subsequent active region). The tunnel junction may not provide optical gain at least within an operational wavelength range of the corresponding laser or a wavelength range that can be amplified by the active regions.
Generating and amplifying laser light using multiple active regions may reduce the electric current required for generating a desired optical output mode (e.g., the fundamental mode) having a desired output power. In some cases, the output power of a first laser having multiple active regions can be larger than that of a second laser having one active region but otherwise being identical to the first laser. For example, for pulsed operation, an amount of optical power generated for a given peak current of a pulsed current, may be increased by including plurality of active regions that are serially pumped by a pulsed injection current, across the laser waveguide and the laser cavity. In some embodiments, the electric current may sequentially pass through the active regions via tunnel junctions disposed between the active regions. A tunnel junction may comprise at least one pn junction configured to enable transmission of charge carriers (e.g., electrons or holes) between n-type and p-type regions of the tunnel junction via quantum tunneling, thereby enabling current to pass from n-type semiconductor to p-type semiconductor (or visa versa). In some cases, the plurality of active regions may comprise a plurality of active regions parallel to a substrate on which the laser is grown or fabricated, or a lower cladding on which the waveguide layer is disposed. A tunnel junction may be positioned or disposed between two subsequent (e.g., two consecutive) active regions where a first active region is above the tunnel junction and a second active region is below the tunnel junction.
In some cases, multiple active regions in a laser cavity may provide more gain to a high order vertical mode of the corresponding waveguide layer compared to the fundamental vertical mode of the waveguide layer. As such, the high order mode may have a lower threshold compared to the fundamental vertical mode, if both modes receive the same level of optical feedback. So while multiple gain regions may generate a larger optical output power (compared to a single gain region), the corresponding optical output beam may have a high order vertical intensity profile comprising two or more peaks and at least a low power region (a null) along the vertical direction. Some of the designs and methods described above with respect to placement of a grating layer within the waveguide layer may be used to reduce the lasing threshold for the fundamental vertical mode and thereby maintaining a fundamental vertical optical output intensity profile in a laser cavity having multiple gain regions. As such, some of the laser designs proposed and described below, may generate an optical output having a fundamental vertical intensity profile but with a larger optical power compared to that of a laser having a single gain region (described above), for a given peak current provided to both lasers. In some examples, the optical output may comprise pulsed optical power. Some of the laser designs proposed and described below, may comprise vertically stacked quantum wells and tunnel junctions.
In some cases, the electrical current injected into the one or more gain regions is turned on and off (e.g., periodically) to generate one or more laser pulses. Given the difficulty of generating short electrical pulses having high peak currents, in some cases, several gain regions separated by tunnel junctions may be included in the laser cavity to reduce the magnitude of a current needed to generate a laser pulse having high peak power. In some cases, the gain regions and the tunnel junctions can be monolithically stacked in series.
In some cases, the slope efficiency of a laser comprising multiple gain regions may scale (e.g., linearly) with a number (N) of the gain regions included in the laser cavity (e.g., within the waveguide layer). In some cases, the output optical power of such laser may increase by N-fold compared to the output optical power of a laser having a single active region (e.g., the lasers described above with respect to
The tunneling region 1502 may comprise a material similar or different from the waveguide material. In some examples the tunneling region 1502 and the waveguide layer may comprise the same compound semiconductor but with different stoichiometric ratios. In some cases, the tunneling region 1502 may comprise a highly doped material having a dopant concentration larger than that of the waveguide material. In some examples, a dopant (e.g., p or n dopant) concentration in the tunneling region 1502 can between 4 to 6 times, 6 to 10 times, 10 to 20 times, 20 to 50 time, or 50 to 100 time larger than that of the waveguide region 201. In some cases, the tunneling region 1502 may comprise two or more layers having different types of dopants and/or doping concentrations, and/or different materials (e.g., semiconductor materials). The first and the second active regions 101a, 101b may positioned such that they provide optical gain to at least one optical mode confined in the waveguide layer 201, upon being pumped. In some implementations, at least one active region may be within the ridge 100. In some implementations, at least one active region may coincide with a peak of an intensity profile (vertical profile) associated with a vertical mode of the waveguide layer 201.
In some cases, the active regions 101a and 101b may comprise an undoped or lightly doped regions. In some cases, the undoped or lightly doped region may comprise one or more quantum wells configured to provide optical gain upon being pumped by a current flowing through the corresponding gain region. The active regions 101a and 101b may comprise the same or different number of quantum wells.
In some implementations, a portion of the first waveguide region 201a, above the first active layer 101a, a portion of the second waveguide region 201b, below the tunneling region 1502 and above the second active layer 101b, may comprise a first dopant type (p or n). In some implementations, a portion of the first waveguide region 201a, below the first active layer 101a and above the tunneling region 1502, and a portion of the second waveguide region 201b below the second active layer 101b, an above the cladding material, may comprise a second dopant type (p or n) different from the first dopant type.
The waveguide layer 201 can comprise materials similar to the waveguide layer 102 (in
In some implementations, the waveguide layer 201 may comprise a layered waveguide similar to the layered waveguide structure 105 described above with respect to
In some cases, the first 101a and the second 101b the active regions (or gain layers) each may comprise a vertical layered structure comprising 1 to 3, 3 to 5, 5 to 10, 10 to 15, or 15 -20 single quantum wells (SQWs). The tunneling region 1502 is substantially parallel to the gain regions 101a and 101b, and may have a thickness along a direction parallel to a growth direction of tunneling region 1502 (along the y-axis). The thickness of the tunneling region can be from 10 to 20 nm, 20 to 30 nm, 30 to 40 nm, 40 to 50 nm or any ranges formed by these values or larger or smaller.
The laser 1500 includes a grating or grating layer 106 that provides optical feedback to one or more vertical optical modes confined by the waveguide layer 201. In some examples, the grating layer 106 may be configured to provide different levels of optical feedback to different vertical optical modes confined in the waveguide layer 201. For example, placing the grating layer 106 in different positions along the vertical direction (e.g., along the y-axis) may generate different levels of optical feedback for different vertical modes. In some cases, the grating layer 106 may be disposed within the waveguide layer 201. In some such cases, the grating layer 106 may be positioned between the first 101a and the second 101b gain regions (e.g., within the tunnel junction 1502). In some cases, the grating layer 106 may be aligned with respect to waveguide layer 201 so as to provide more optical feedback to a fundamental vertical mode 1504a of the waveguide layer 201 compared to higher order vertical optical modes (e.g., the second order vertical mode 1504b). For example, the grating layer 106 may be disposed at or near a peak intensity or peak magnitude of the optical field associated with the fundamental optical mode. In some cases, the intensity or the magnitude of an optical field associated with the fundamental vertical mode 1504a (the fundamental mode) and the second order vertical 1504b can be different from those of the fundamental vertical mode 104a and the second vertical 104b described above with respect to
With continued reference to
The active regions 101a, 101b, can be pumped by an injection current flowing from the top electrode 108 toward the cladding 103, passing through the first active region 101a, the tunneling region 1502, and the second active region 101b. In some cases, the injection current may be generated by applying a voltage to the top electrode 108. A bottom electrode may be in electrical contact with the cladding 103 and configured to receive the injection current transmitted through the active regions. The bottom electrode may be kept at a lower voltage compared to the top electrode 108. In some cases, the bottom electrode may be connected to an electrical ground.
In some embodiments, the position of the grating 106 and the positions of the first and the second active regions 101a, 101b, with respect the waveguide layer 201 may be configured so that their combined effects makes the lasing threshold for the fundamental vertical optical mode 1504a smaller than a lasing threshold for at least one higher order vertical optical mode (e.g., the second order mode 1504b). For example, the grating 106, the first active region 101a and the second active region 101b, may be positioned such that a lasing threshold for the fundamental vertical optical mode 1504a is smaller than a lasing threshold for at least one higher order vertical optical mode by a desired amount. In some cases, alignment between the vertical optical modes, the grating layer 106, and the gain region may be designed such that when an injection current larger than a threshold injection current for the fundamental mode is provided to the laser 1500, the higher order mode does not lase while the fundamental mode lases. In some cases, the grating 106, the first active region 101a and the second active region 101b, may be positioned such that a lasing threshold for the fundamental vertical optical mode 1504a is smaller than the lasing thresholds for all higher order vertical optical modes. In some cases, the grating 106, the first active region 101a and the second active region 101b, may be positioned such that a lasing threshold for the fundamental vertical optical mode 1504a is smaller than the lasing thresholds for most higher order vertical optical modes.
In some cases, at least one of the first and the second active regions 101a, 101b, may overlap with a peak (e.g., intensity peak) of at least one higher order vertical optical mode (e.g., the second order mode 1504b). In some examples, the grating layer 106 may overlap with a peak of the fundamental vertical optical mode. In some such examples, at least one of the first and the second active regions 101a, 101b, may not overlap with the peak of the fundamental mode. In some cases, the grating 106 may overlap with a null of the at least one higher order optical mode (e.g., the second order mode 1504b).
A peak of a mode (an optical mode) may include a position where a peak magnitude of the optical field or intensity associated with the mode is located. A null of a mode may include a position where the magnitude of the optical field or intensity associated with the mode is substantially zero.
In various implementations, the active regions 101a, 101b, can be positioned symmetrically or asymmetrically along the vertical direction (e.g., along the y-axis) with respect to the tunneling region 1502 or the tunnel junction therein. For example, one of the active regions 101a, 101b, can be vertically closer to the tunneling region 1502 or the tunnel junction therein. In some cases, the active regions 101a, 101b, can be positioned symmetrically or asymmetrically along the vertical direction (e.g., along the y-axis) with respect to the grating layer 106. For example, one of the active regions 101a, 101b, can be vertically closer to the grating layer 106. The grating layer 106 may be disposed inside or outside of the tunneling region 1502. The grating layer 106 can be closer to second waveguide layer 201b or closer to the first waveguide layer 201a. The tunneling region 1502 can be closer to second waveguide layer 201b or closer to the first waveguide layer 201a. In some implementations, other configurations are possible. In some cases, the positions and the relative alignments of the active regions 101a, 101b, the tunneling region 1502, and the grating layer 106 inside or outside of the waveguide layer 201, may be determined for decreasing the lasing threshold for a vertical mode of the waveguide layer 201 compared to other vertical modes of the waveguide layer 201, without any further geometrical constraints.
In some implementations, the designs described above with respect to positioning two or more active regions (e.g., active regions 101a and 101b) and the grating layer 106 to selectively reduce a number of vertical modes lasing (oscillating) within a laser waveguide or cavity, is not limited to ridge waveguide architectures (e.g., schematically illustrated in
The laser 1600 includes two active regions 101a, and 101b that upon being pumped, they can provide optical gain to the optical modes mainly confined within the buried waveguide layer 201. The optical modes are vertically confined by the upper cladding 1100 and the lower cladding 103, and laterally confined by the regions 112. Additionally, the laser 1600 may include a tunneling region 1502 positioned between the first active region 101a and the second active region 101b to allow electric current flow between these active regions. The waveguide region 201 may comprise a first waveguide region 201a above the tunneling region 1502 and a second waveguide region 201b, below the tunneling region 1502. The first active region 101a can be within the first waveguide region 201a and the second active region 101b can be within the second waveguide region 201b.
A top electrode 108 is disposed on the upper cladding 1100 and is configured to provide electrical contact to the cladding 1100. The top electrode 108 may comprise a conducting material (e.g., a metal). In some cases, the laser 1600 may include a bottom electrode configured to provide electrical contact to the lower cladding 103. The top electrode 108 may be used to generate an electrical current (an injection current) flowing through the first and the second active regions 101a and 101b, to pump these active regions and for providing optical gain to the optical modes of the laser 1600. The electric current may flow from the top electrode, which is kept at a first electric potential, to the bottom electrode, which is kept at second potential different from the first potential. In some cases, the first potential can be higher than the second potential. In some cases, the bottom electrode and or the lower cladding 103 may be connected to ground.
In certain embodiments, as schematically illustrated in
As described above, the first active region 101a, the second active region 101b, and the grating layer 106 may be positioned within the waveguide layer 201 in the laser 1500 or laser 1600 such that a threshold (e.g., a threshold injection current) for lasing of a first vertical mode (e.g., the fundamental mode 1504a) of the waveguide layer 201 is smaller than a threshold for lasing of at least a second vertical mode (e.g., the second order mode 1504b) different from the first vertical mode. In some examples, the threshold for lasing of the fundamental mode 1504a can be smaller than that of the second order mode 1504b and one or more other vertical modes (higher order vertical modes). In some examples, the threshold for lasing of a vertical mode (e.g., the fundamental mode 1504a) can be larger than all other vertical modes (higher order vertical modes) of the waveguide layer. In some examples, the threshold for lasing of a vertical mode (e.g., the fundamental mode 1504a) can be larger than most other vertical modes of the waveguide layer. As such, a placement of the first active region 101a, the second active region 101b, and the grating layer 106 may result in suppression of the lasing of one or more vertical modes (e.g., the second order mode 1504b, a third order mode, etc.), while allowing the lasing of the fundamental mode 1504a. In some cases, for a given placement of the first active region 101a, the second active region 101b, and the grating layer 106, providing an injection current having a magnitude larger than the threshold current for the first vertical mode to the laser 1500 or laser 1600, may result in generation of a single-vertical-mode laser beam (e.g., a large area beam or a beam having a large waist size). The single-vertical-mode optical output beam may have a cross-sectional intensity profile associated with the fundamental vertical mode 1504a (e.g., a Gaussian distribution). In some examples, a portion of the single-vertical-mode output optical beam may include an intensity distribution associated with a higher order vertical mode. In some such examples, a peak or an average magnitude of such intensity distribution may be suppressed by 10 dB, 100 dB, or 150 dB compared to a peak or an average magnitude of intensity distribution associated with the fundamental vertical mode, in the single-vertical-mode output optical beam.
In some cases, in order to generate a single-vertical-mode laser beam, the positions of the first active region 101a, the second active region 101b, and the grating layer 106 may be determined via an iterative calculation process. The process may begin with providing a first initial position of a first active region, a second initial position of a second active region, and a third initial position of the grating layer 106, and calculating at least a first vertical optical mode and at least a second vertical optical mode confined by the waveguide layer 201 for the first and the second initial positions of the first and second active regions and the third initial position of the grating layer 106. Next, a first product of an overlap (e.g., an overall integral) of the first vertical optical mode with the grating (Γgrt1) and an overlap of the first vertical optical mode with the first and the second active regions (Γqw11 and Γqw21 respectively), and a second product of an overlap of the at least one second vertical optical mode with the grating (Γgrt2) and an overlap of the at least one second vertical optical mode with the first and the second active regions (Γqw12 and Γqw22 respectively), are calculated. If the first product (Γqw11 + Γqw21 )×Γgrt1 is not larger than the second product (Γqw12 + Γqw22) × Γgrt2 by a threshold value, the positions of the active regions 101a, 101b, and the grating layer 106 may be adjusted so as to increase the first product and/or decrease the second product. After the first adjustment of the positions the first and the second products are calculated and compared again, if still the first product is not larger than the second product by the threshold value, the positions may be adjusted for a second time. This process may be repeated (iteratively) until the first product becomes larger than the second product by the threshold value. In some cases, the process described above is performed by a computing system comprising a non-transitory memory and at least one processor. The processor may perform the process by executing machine-readable instructions stored in the non-transitory memory. The threshold value may be a value stored in the memory and/or provided by a user via a user interface. In some cases, the processor may determine the threshold value based on a desired or target suppression level of a second vertical mode (e.g., a 2nd or higher order vertical mode) compared to a first vertical mode (e.g., the fundamental mode 1504a) of the waveguide layer 201. In some cases, in each iteration of the calculation process described above, after adjusting positions and before calculating the first and the second products, the processor may re-calculate the first vertical optical mode and the second vertical optical mode and determine perturbations of the first vertical optical mode and the second vertical optical mode resulting from the adjusted positions of the first and the second active regions and the grating layer. Using this process, the threshold for lasing of a single vertical mode (e.g., the fundamental mode 1504a) may be selectively reduced and/or the threshold for lasing of other vertical modes (e.g., second order mode 1504b) may be increased to make the threshold for lasing of the first vertical mode larger than that of the first vertical mode by the threshold amount.
In some examples, the process described with respect to
In certain embodiments, the product (Γqw1+ Γqw2)×Γgrat for the fundamental mode 1504a can be in a range of about 1-20 dB (e.g., 1 dB, 3 dB, 10 dB, 15 dB, 20 dB or any value in a range/sub-range defined values between 1 dB and 20 dB) greater than the product (Γqw1+ Γqw2)×Γgrat for other higher order modes present in the waveguide to selectively reduce the lasing threshold for the fundamental mode 1504a.
With reference to the process shown in
In some cases, the positions of the grating layer 106 in the waveguide layer 201 of the laser 1500 or 1600, may not overlap with the location of any peak magnitude of the optical field or intensity associated with the fundamental vertical optical mode 1504a.
In some cases, the positions of the gain regions 101a and 101b in the layer 106 in the waveguide layer 201 of the laser 1500 or 1600, may not overlap with the location of any peak magnitude of the optical field or intensity associated with the fundamental vertical optical mode 1504a.
In some cases, the positions of the grating layer 106 in the waveguide layer 201 of the laser 1500 or 1600, may not overlap with the location of any null of the optical field or intensity associated with the higher order verticals optical modes (e.g., the second vertical optical mode 1504a).
In some cases, the positions of the gain regions 101a and 101b in the layer 106 in the waveguide layer 201 of the laser 1500 or 1600, may not overlap with the location of any peak magnitude of the optical field or intensity associated with the higher order verticals optical modes (e.g., the second vertical optical mode 1504a).
In some cases, the positions of the grating layer 106 in the waveguide layer 201 of the laser 1500 or 1600, may not overlap with the location of any peak magnitude of the optical field or intensity associated with the fundamental vertical optical mode 1504a.
In certain such embodiments, the second order mode 1504b may have comparable or better overlap with one or both the active regions 101a and 101b, only the fundamental mode 1504a lases because the feedback from the grating layer 106 for the second order mode 1504b (or the coupling between the grating layer 106 and the second order mode 1504b) is much lower as compared to the feedback from the grating layer 106 for the fundamental mode 1504a (or the coupling between the grating layer 106 and the fundamental mode 1504a).
In some cases, the grating layer 106 is positioned within the waveguide 201 layer such that the grating layer 106 coincides with a null or a minimum of the second order mode 1504b, and at least one of the active regions 101a and 101b coincide with a null or a minimum of a third order mode (e.g., mode 104c shown in
In various implementations, an optical power of light outputted from the laser 1500 and laser 1600 can be from 10 to 50 W and the placement of the grating 106 and the active regions 101a and 101b may result in a side mode suppression ratio of light outputted from the laser 1500 to be from larger than 10 dB, 100 dB, or 150 dB.
In some cases, the laser designs, structures, and design methods described above with respect to laser having two active regions may be used to design lasers having more than two active regions and can generate an optical output beam comprising a single vertical mode or having a vertical intensity profile dominated by a single vertical mode (e.g. the fundamental vertical mode). In some such cases, the active regions may be stacked in a vertical direction (e.g., a direction of along which different layers are disclosed or grown) such that each active region is below a subsequent active region. In some examples, a tunnel junction may be disposed between two consecutive active regions to enable an electric current (e.g., injection current) to serially flow from one active region to another active region. As example laser with multiple active regions may include a waveguide layer configured to support a first vertical optical mode (e.g., the fundamental vertical mode) and at least a second vertical optical mode (e.g., the second or third order optical modes), a first active region at a first position with respect to the waveguide layer, a second active region at a second position with respect to the waveguide layer, a third active region at a third position with respect to the waveguide layer, a first tunneling region below the first position and above the second position, and a second tunneling region below the second position and above the third position. The laser may include a grating at a fourth position with respect to the waveguide layer, which provides optical feedback to one more vertical modes of the waveguide layer. The active regions and the grating layer may be aligned with respect to the a vertical optical field or intensity profile of the first and the second vertical mode such that a first product of an overlap of the first vertical optical mode with the grating and an overlap of the first vertical optical mode with the first, second, and the third active regions is greater than a second product of an overlap of the second vertical optical mode with the grating and an overlap of the second vertical optical mode with the first, second, and the third active regions.
In certain embodiments, the laser 1500 may comprises one or more features described above with respect to the laser in
In certain embodiments, the waveguide layer 201 and the high index region of the ridge may support two, three or more modes vertical optical modes, and the placement of the grating layer 106 and the active regions 101a, 101b may result in a lower lasing threshold for fundamental vertical mode compared to the higher order modes. The active regions 101a, 101b may be disposed positioned within the waveguide layer 201. Various methods and designs described above with respect to making the lasing threshold of the fundamental vertical mode smaller than that than those of the higher order modes may be used for a laser having at least two active regions and a high index region.
Although for various embodiments of lasers discussed herein, the first and the second active regions 101a, 101b, the grating layer 106, the tunneling region 1502, and the tunnel junction can be described as being positioned inside the waveguide layer 201, it should be appreciated that one or more of these regions can be outside of the waveguide layer 1502. For example, with reference to
Certain embodiments described herein can be configured to output optical power greater than or equal to about 10 mW (e.g., greater than or equal to about 20 mW, greater than or equal to about 30 mW, greater than or equal to about 50 mW, greater than or equal to about 75 mW, greater than or equal to about 100 mW, greater than or equal to about 150 mW) and/or less than or equal to 50 W (e.g., less than or equal to 25 W, less than or equal to 10 W, less than or equal to 5 W, less than or equal to 1 W), or any optical power in a range/sub-range defined by these values. Certain embodiments described herein are configured to output a single vertically confined mode. Accordingly, the light output from certain embodiments described herein have a large side mode suppression ratio (SMSR). For example, the SMSR of light output from certain embodiments described herein can be between about 10 dB and about 150 dB (e.g., between about 10 dB and about 20 dB, between about 15 dB and about 30 dB, between about 20 dB and about 40 dB, between about 30 dB and about 60 dB, between about 40 dB and about 80 dB, between about 50 dB and about 100 dB, between about 60 dB and about 120 dB, between about 70 dB and about 140 dB, or any value in any range/sub-range defined by these values.).
Although for various embodiments of lasers discussed herein, the active region and/or the grating layer can be described as being positioned at the peak and/or at the null of the vertically confined mode, it should be appreciated that the active region and/or the grating layer can be positioned near or in proximity to the peak and/or near or in proximity to the null of the vertically confined mode to increase/decrease lasing threshold of the vertically confined mode.
In certain embodiments, a computer system is used for some or all of the calculations described herein. For example, the computer system can comprise hardware (e.g., at least one microprocessor) operative to execute software (e.g., code stored on computer-readable non-transitory memory media). It will be appreciated that one or more portions, or all of the code may be remote from the user and, for example, resident on a network resource, such as a LAN server, Internet server, network storage device, etc. In certain embodiments, the computer system comprises a standard personal computer. The computer system can comprise standard communication components (e.g., keyboard, mouse, trackball, touchpad, toggle switches) for receiving user input (e.g., commands and/or data from a human operator), and can comprise standard communication components (e.g., image display screen, alphanumeric meters, printers) for displaying and/or recording output data, and computer-readable non-transitory memory media (e.g., random-access memory (RAM) integrated circuits; hard-disk drives).
Various additional example embodiments of the disclosure can be described by the following examples:
Example 1. A laser comprising:
Example 2. The laser of Example1, wherein the active region overlaps with a peak of the fundamental optical mode.
Example 3. The laser of Example1, wherein the active region overlaps with a null of the at least one higher order optical mode.
Example 4. The laser of Example1, wherein the grating overlaps with a peak of the fundamental optical mode.
Example 5. The laser of Example1, wherein the grating overlaps with a null of the at least one higher order optical mode.
Example 6. The laser of Example1, wherein an optical power of light outputted from the laser is between about 10 mW and about 50 W.
Example 7. The laser of Example1, wherein a side mode suppression ratio of light outputted from the laser is between about 10 dB and about 150 dB.
Example 8. The laser of Example1, wherein the waveguide comprises a first plurality of layers comprising a first material having a first refractive index and a second plurality of layers comprising a second material having a second refractive index.
Example 9. The laser of Example8, wherein the waveguide is a weakly confined waveguide.
Example 10. The laser of Example1, wherein the active region is over the waveguide.
Example 11. The laser of Example1, wherein the active region within the waveguide.
Example 12. The laser of Example1, wherein the grating structure is within the waveguide.
Example 13. The laser of Example1, wherein the waveguide is between and vertically confined by a first region and a second region, the first region comprising a first material having a first refractive index, the second region comprising a second material having a second refractive index, the waveguide comprising a third material having a third refractive index, the first refractive index less than the third refractive index, and the second refractive index less than the third refractive index.
Example 14. The laser of Example13, wherein the waveguide is laterally confined by at least one region comprising a fourth material having a fourth refractive index.
Example 15. The laser of Example14, wherein the fourth refractive index is substantially equal to the first refractive index and/or the second refractive index.
Example 16. The laser of Example13, wherein the fourth material is electrically blocking or insulating.
Example 17. A method for designing a laser comprising a waveguide, an active region, and a grating, the method comprising:
Example 18. The method of Example17, wherein the first optical mode is a fundamental optical mode supported by the waveguide and the at least one second optical mode is a second order optical mode and/or a third order optical mode supported by the waveguide.
Example 19. The method of Example17, wherein the position of the active region and the position of the grating are within the waveguide.
Example 20. The method of Example17, wherein the threshold value is 1 dB, 3 dB, 10 dB, 15 dB, 20 dB, or any value in a range/sub-range defined by any of these threshold values.
Example 1. A laser comprising:
Example 2. The laser of Example 1, wherein at least one of the first and the second active regions overlap with a peak of the first higher order vertical optical mode.
Example 3. The laser of Example 1, wherein the grating overlaps with a peak of the fundamental vertical optical mode.
Example 4. The laser of Example 1, wherein the grating overlaps with a null of the first higher order optical mode.
Example 5. The laser of Example 1, wherein the waveguide layer is configured to support a second higher order optical mode, and the grating overlaps with a null of the first or the second higher order optical mode.
Example 6. The laser of Example 5, wherein the grating overlaps with a peak of the fundamental vertical optical mode.
Example 7. The laser of Example 1, wherein a first product of an overlap of the fundamental vertical optical mode with the grating and an overlap of the fundamental vertical optical mode with the first and the second active regions is greater than a second product of an overlap of the first higher order vertical optical mode with the grating and an overlap of the first higher order vertical optical mode with the first and the second active regions.
Example 8. The laser of Example 5, wherein a first product of an overlap of the fundamental vertical optical mode with the grating and an overlap of the fundamental vertical optical mode with the first and the second active regions is greater than a second product of an overlap of the second higher order vertical optical mode with the grating and an overlap of the second higher order vertical optical mode with the first and the second active regions.
Example 9. The laser of Example 1, wherein the first lasing threshold for the fundamental vertical optical mode comprises a first threshold injection current and the second lasing threshold for the first higher order vertical optical mode comprises a second threshold injection current larger than the first threshold injection current, and wherein an injection current larger than the first threshold current provided to the laser generates an optical output beam, a contribution of the first higher order vertical optical modes in the optical output beam being suppressed with respect to a contribution of the fundamental vertical optical mode by at least 10 dB.
Example 10. The laser of Example 5, wherein the first and the second positions of the first and the second active regions, and the third position of the grating are further configured to make the first lasing threshold for the fundamental vertical optical mode smaller than a third lasing threshold for the second higher order vertical optical mode.
Example 11. The laser of Example 10, wherein the first lasing threshold for the fundamental vertical optical mode comprises a first threshold injection current, the second lasing threshold for the first higher order vertical optical mode comprises a second threshold injection current, the third lasing threshold for the second higher order vertical optical mode comprises a third threshold injection current, wherein the third threshold current is larger than the second threshold injection current and the second threshold current is larger than the first threshold injection current.
Example 12. The laser of Example 11, wherein an injection current larger than the first threshold current is provided to the laser generates an optical output beam, and wherein contributions of the first and the second higher order vertical optical modes in the output optical beam are suppressed with respect to a contribution of the fundamental vertical optical mode by at least 10 dB.
Example 13. The laser of Example 12, wherein the injection current sequentially passes through the first active region, the tunnel junction, and the second active region.
Example 14. The laser of Example 1, wherein an optical power of light outputted from the laser is between about 10 mW and about 50 W.
Example 15. The laser of Example 1, wherein a side mode suppression ratio of light outputted from the laser is between about 10 dB and about 150 dB.
Example 16. The laser of Example 1, wherein the waveguide comprises a first plurality of layers comprising a first material having a first refractive index and a second plurality of layers comprising a second material having a second refractive index.
Example 17. The laser of Example 15, wherein the waveguide layer comprises a weakly confined waveguide.
Example 18. The laser of Example 1, wherein at least one of the first and the second active regions is within the waveguide layer.
Example 19. The laser of Example 1, wherein the grating is within the waveguide layer.
Example 20. The laser of Example 1, wherein the waveguide layer is between and vertically confined by a first region and a second region, the first region comprising a first material having a first refractive index, the second region comprising a second material having a second refractive index, the waveguide layer comprising a third material having a third refractive index, the first refractive index less than the third refractive index, and the second refractive index less than the third refractive index.
Example 21. The laser of Example 20, wherein the waveguide is laterally confined by at least one region comprising a fourth material having a fourth refractive index.
Example 22. The laser of Example 21, wherein the fourth refractive index is substantially equal to the first refractive index and/or the second refractive index.
Example 23. The laser of Example 22, wherein the fourth material is electrically blocking or insulating.
Example 24. The laser of Example 1, wherein the tunnel junction comprises a pn semiconductor junction.
Example 25. The laser of Example 1, wherein the third position is between the first and the second positions.
Example 26. The laser of Example 1, wherein the first position is above the second position.
Example 27. The laser of Example 26, wherein the third position is above the second position and below the first position.
Example 28. The laser of Example 1, wherein the tunnel junction is below the first position and above the second position.
Example 29. The laser of Example 28, wherein the third position overlaps with the tunnel junction.
Example 30. A method for designing a laser comprising a waveguide layer, at least two active regions, and a grating, the method comprising:
Example 31. The method of Example 30, wherein the first optical mode is a fundamental vertical optical mode supported by the waveguide layer and the at least one second vertical optical mode is a second order vertical optical mode and/or a third order vertical optical mode supported by the waveguide layer.
Example 32. The method of Example 30, wherein the positions of the first and the second active regions and the position of the grating are within the waveguide layer.
Example 33. The method of Example 30, wherein the threshold value is 1 dB, 3 dB, 10 dB, 15 dB, 20 dB, or any value in a range/sub-range defined by any of these threshold values.
Example 34. The method of Example 30, further comprising providing a fourth position of a tunnel junction between the first and the second positions.
Example 35. The method of Example 34, calculating the vertically confined first vertical optical mode and the vertically confined second vertical optical mode comprises, calculating the vertically confined first vertical optical mode and the vertically confined second vertical optical mode for the fourth position of the tunnel junction
Example 36. The method of Example 34, wherein the tunnel junction comprises a pn semiconductor junction.
Example 37. The method of Example 30, wherein the first position is above the second position.
Example 38. The method of Example 37, wherein the third position is above the second position and below the first position.
Example 39. A laser comprising:
Example 40. The laser of Example 39, wherein the first optical mode is a fundamental vertical optical mode supported by the waveguide layer and the at least one second vertical optical mode is a second order vertical optical mode or a third order vertical optical mode supported by the waveguide layer.
Example 41. A laser comprising:
Example 42. The laser of Example 41, wherein the first optical mode is a fundamental vertical optical mode supported by the waveguide layer and the at least one second vertical optical mode is a second order vertical optical mode and/or a third order vertical optical mode supported by the waveguide layer.
Example 43. A laser comprising:
Example 44. The laser of Example 43, further comprising a grating within the waveguide layer, the grating configured to provide feedback for the fundamental vertical optical mode.
Example 45. The laser of Example 43, wherein a first product of an overlap of the fundamental vertical optical mode with the grating and an overlap of the fundamental vertical optical mode with the two active regions is greater than a second product of an overlap of a higher order vertical optical mode with the grating and an overlap of the higher order vertical optical mode with the two active regions.
Example 46. The laser of Example 43, further comprising a tunnel junction between the two active regions.
Example 47. The laser of Example 46, wherein the tunnel junction comprises a pn semiconductor junction.
Example 48. The laser of Example 1, wherein at least one of the first and the second active regions is inside the waveguide layer.
Example 49. The laser of Example 1, wherein the grating is inside the waveguide layer.
Example 49. The laser of Example 1, wherein the tunnel junction is inside the waveguide layer.
Example 1. A laser comprising:
Example 2. The laser of the Example 1, further comprising a grating within the waveguide layer, the grating configured to provide feedback for the fundamental mode.
Example 3. The laser of the Example 1, wherein the waveguide layer comprises a first plurality of layers comprising a first material having a first refractive index and a second plurality of layers comprising a second material having a second refractive index.
Example 4. A laser comprising:
While the foregoing detailed description discloses several embodiments, it should be understood that this disclosure is illustrative only and is not limiting. It should be appreciated that specific configurations and operations in accordance with certain embodiments described herein can differ from the particular example described herein, and that the example apparatus and methods described herein can be used in other contexts. Additionally, components can be added, removed, and/or rearranged. Additionally, processing steps can be added, removed, or reordered. A wide variety of designs and approaches are possible.
Various modifications to the embodiments described herein may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the embodiments shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. The word “exemplary” is used exclusively herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of the device as implemented.
Certain features that are described in this specification in the context of separate embodiments also can be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment also can be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described herein should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.
This application is a continuation in part of the U.S. Appl. No. 17/898305 filed on Aug. 29, 2022 which is a continuation of the U.S. Appl. No. 16/823823 filed on Mar. 19, 2020 that is Issued as the U.S. Pat. No. 11431149, on Aug. 30, 2022 and claims the benefit of priority to U.S. Provisional Appl. No. 62/822,677 filed Mar. 22, 2019. Each of the applications referenced in this paragraph is hereby incorporated herein by reference in its entirety.
| Number | Date | Country | |
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| 62822677 | Mar 2019 | US |
| Number | Date | Country | |
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| Parent | 16823823 | Mar 2020 | US |
| Child | 17898305 | US |
| Number | Date | Country | |
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| Parent | 17898305 | US | |
| Child | 18157793 | US |
