Patent Application
20250158350
The invention relates to a semiconductor laser having a radiation guidance element, more particularly an optical element or light guide, and to a corresponding production method. The invention also relates to a radiation transmission element, more particularly radiation exit window for a laser housing, having at least one optical element, and to a corresponding production method.
One object to be achieved is that of specifying a semiconductor laser which is efficiently encapsulated and can be produced efficiently. Another object is that of a specifying semiconductor laser having a self-adjusting radiation guidance element, more particularly an optical element or light guide. A further object is that of specifying a corresponding radiation transmission element, more particularly a radiation exit window for a laser housing. The objects are achieved by the devices and the production methods having the features of the independent claims. Preferred developments are subjects of the dependent claims.
According to one embodiment, the semiconductor laser comprises a laser diode which has an active zone for generating laser radiation and has a radiation exit region via which the laser radiation can exit the laser diode. The semiconductor laser also has a radiation guidance element which is arranged in the radiation exit region on the laser diode and is connected monolithically to the laser diode. The radiation guidance element comprises a substance or consists of a substance which can be applied by means of the laser radiation on the laser diode. More preferably, the radiation guidance element is arranged in the radiation exit region directly (without interlayer) on the laser diode or directly on a dielectric mirror.
Accordingly, the radiation guidance element can be applied in a self-aligning manner precisely on the beam exit region, by operating the laser diode for applying the radiation guidance element.
The radiation guidance element is preferably stable towards the laser radiation, also called “radiation-stable”, meaning that in an operating state it does not degrade, or not substantially, within a typical total operating time for the semiconductor laser.
The laser diode may in principle be any desired semiconductor laser diode.
Because of the particularly high power densities, the effect known as the optical tweezers effect is particularly pronounced for edge-emitting semiconductor laser diodes. In this case, as a result of the high power densities, organic and inorganic soiling/compounds are picked up from the ambient air and deposited on the laser facet. The high energy densities in the region of the laser facet allow decomposition and deposition/accumulation of particles and decomposition products to take place at the facet. In this case, there is an interaction with the emitted radiation, leading in turn to additional heating of the facet. As a result of the relationship described above, self-reinforcing effects may occur that may ultimately result in destruction of the laser (COD, catastrophic optical damage).
According to one embodiment, the radiation guidance element is designed as a protective element reducing such effects. The element may in particular be designed in such a way that it enables operation of the semiconductor laser in normal ambient air. For this it may have a certain minimum thickness. As a coupling element, however, it may also bridge the distance between laser and a radiation outcoupling element, as is explained more precisely later on.
Accordingly, the laser diode is preferably an edge-emitting laser diode. In this case, the radiation exit region is a region of the laser facet, meaning that the radiation guidance element is arranged in the radiation exit region on the laser facet, preferably directly on the laser facet, and is connected monolithically to the laser facet.
As mentioned, however, the diode may in principle be any desired semiconductor laser diode, more particularly a vertical cavity surface emitting laser (VCSEL) or else a photonic crystal surface emitting laser (PCSEL). In the case of a VCSEL, the radiation guidance element may be applied—preferably directly—on a distributed Bragg reflector, via which the laser radiation exits in operation, or—preferably directly—on a substrate via which the laser radiation exits in operation. In the case of a PCSEL, the radiation guidance element may be applied—preferably directly—on a photonic crystal of the PCSEL.
The substance may in particular be an inorganic substance. The substance may comprise or consist of silicon, aluminum, tantalum, titanium or hafnium.
The substance may, for example, be a dielectric, such as: silicon dioxide SiO2, aluminum oxide Al2O3, tantalum oxide TaO, tantalum dioxide TaO2, ditantalum pentaoxide Ta2O5, titanium dioxide TiO2, hafnium dioxide HfO2. Experimentally, particularly good results have been achieved with silicon dioxide SiO2.
The radiation guidance element may be designed as a radiation outcoupling element. This means that the radiation guidance element has a radiation outcoupling face, not connected to a further optical element, via which the radiation can be delivered to an atmosphere.
The radiation outcoupling element may be designed for shaping the laser radiation (called “optical element” below), and in particular may be designed as a refractive lens.
The lens may be designed in such a way that the laser radiation is widened by the lens effect, to enable operation of the semiconductor laser in normal ambient air. Alternatively, the radiation outcoupling element may enable self-adjusting focusing of the laser beam, to realize optimization of the beam profile. Alternatively, in addition to the radiation guidance element, there may be a radiation outcoupling element present that is connected monolithically to the radiation guidance element. The radiation guidance element may then constitute a coupling element (more particularly a light guide) with which the laser radiation is guided from the laser diode to the radiation outcoupling element. In the case of this embodiment as well, the beam outcoupling element may be configured for shaping the laser radiation. The beam outcoupling element may be any desired lens, more particularly a refractive lens, or else a prism which changes a direction of propagation of the laser radiation.
In this case, the radiation outcoupling element may be situated after the radiation guidance element along a beam path of laser radiation which can be generated with the semiconductor laser. This means that laser radiation generated when a laser diode is active is transmitted first through the radiation guidance element and then through the radiation outcoupling element. The semiconductor laser may further comprise a support at or on which the semiconductor laser and optionally the radiation outcoupling element are arranged. In particular, the laser and optionally the radiation outcoupling element may be mounted thereon.
According to one embodiment, the semiconductor laser has multiple laser diodes. An individual laser diode may likewise have multiple emission points. For example, the semiconductor laser may comprise a VCSEL array or an edge emitter having multiple laser ridges (laser bars).
Where multiple laser diodes and/or laser diodes having multiple emission points are present, there are preferably also a plurality of the above-described radiation guidance elements present; the semiconductor laser preferably has exactly the same number of radiation guidance elements as emission points.
The laser diode may be configured to emit light in the visible spectral range, more particularly in the blue spectral range. The semiconductor laser described is used preferably in a head-up display of a motor vehicle or as a beam source in a laser projector.
In a method for producing the above-described semiconductor laser, in the step S1 a laser diode which has an active zone for generating laser radiation and has a radiation exit region is provided, and then in step S2 a radiation guidance element is applied to the laser diode in the radiation exit region. The step S2 comprises the substep of exposing (S2a) the laser diode to an atmosphere with a precursor, for example a metal organyl, and optionally a nitrogen and/or oxygen donor which can be induced to react in a chemical reaction by the laser radiation. The step S2 also comprises the substep of operating S2b the laser diode, so that the chemical reaction is induced and the precursor is converted into a substance which forms the radiation guidance element monolithically in the radiation exit region on the laser diode. The optional addition of oxygen prevents the deposition of carbon on the facet.
The laser diode may, as discussed earlier on, be an edge-emitting laser diode. In that case the radiation exit region is a laser facet and the radiation guidance element is arranged on the laser facet, preferably directly. Moreover, the laser diode may be a VCSEL or else a PCSEL. The radiation guidance element is preferably radiation-stable and more preferably a protective element, and preferably enables operation of the semiconductor laser in normal ambient air.
The precursor may in particular be an inorganic precursor. Correspondingly, the substance may be an inorganic substance. The precursor may comprise or consist of silicon, aluminum, tantalum, hafnium or titanium. Correspondingly, the substance may comprise or consist of silicon, aluminum, tantalum, hafnium or titanium.
Experimentally, particularly good results have been achieved with SiO2. Here, a volatile silicone (SixHyCz), e.g., silane (SixH2x), is used as precursor. It reacts with oxygen O2 from the atmosphere to give silicon dioxide SiO2
SixHyCz+O2->SiO2+H2O (+stable Six-oHy-mCz-n)
The Si here may be replaced by a further metal for which the oxide formed has a suitable refractive index.
As mentioned earlier on, the radiation guidance element may be designed as a radiation outcoupling element, in which case it may be suitable for shaping the laser radiation. Alternatively, as mentioned earlier on, additionally to the radiation guidance element, there may be a radiation outcoupling element which is connected monolithically to the radiation guidance element.
A corresponding production method additionally comprises the step S1a of providing the radiation outcoupling element and the step S1b of arranging the radiation outcoupling element relative to the laser diode in such a way that in operation of the laser diode, the laser radiation is transmitted through the radiation outcoupling element. Accordingly, subsequently in step S2a, both the laser diode and the radiation outcoupling element are exposed to the atmosphere with the precursor, and in step S2b, during operation of the laser diode, the radiation guidance element is formed in the radiation exit region on the laser diode such that it connects the laser diode monolithically to the radiation guidance element.
As mentioned earlier on, the semiconductor laser may further comprise a support at or on which the semiconductor laser and optionally the radiation outcoupling element are arranged. As mentioned earlier on, the semiconductor laser may have multiple laser diodes, and in that case there may be a plurality of the radiation guidance elements generated. The laser diode may be configured to emit light in the visible spectral range, more particularly in the blue spectral range. The semiconductor laser described is preferably used in a head-up display of a motor vehicle or as a beam source in a laser projector.
According to one embodiment, a radiation transmission element, more particularly a radiation exit window for a laser housing, comprises a base element, more particularly a radiation exit window base element, and one or more optical elements arranged on the base element and connected monolithically to the base element. The optical elements again comprise a substance which can be applied by means of laser radiation on the base element, or consist thereof.
The base element may in particular be a radiation exit window base element, and in that case may preferably be a planar or predominantly planar sheet which is transparent to laser radiation.
Similarly to the semiconductor laser with radiation guidance element, described earlier on, the optical element or elements may be generated in a self-aligning manner on the base element, by operating a laser diode for applying the one or more optical elements.
The optical element is designed for shaping the laser radiation. This element may be a refractive lens. The lens may be designed in such a way that the laser radiation is widened by the lens effect. The substance may be the substances mentioned earlier on, more particularly silicon dioxide.
According to one embodiment, an optoelectronic device comprises one or more semiconductor laser diodes which each have an active zone for generating laser radiation and have a hermetic laser housing in which the semiconductor laser diodes are arranged. The radiation exit window described above is part of the hermetic laser housing. The laser diodes are arranged relative to the radiation exit window in such a way that each laser diode is assigned one of the optical elements, through which the laser radiation of the respective laser diode can exit in an operating state.
The laser diodes may be laser diodes of one of the types mentioned earlier on, for example edge-emitting laser diodes or a VCSEL array, and application in a head-up display or as a beam source in a laser projector is preferred.
In a method for producing a corresponding radiation transmission element, more particularly radiation exit window, the radiation transmission element is provided first in the step S21. Subsequently, the optical element or elements is or are applied to the radiation transmission element in the step S22. In this case, the radiation transmission element is first exposed (step S22a) to an atmosphere with a precursor which can be induced to react in a chemical reaction by laser radiation. Laser radiation is then generated, so that the chemical reaction is induced by the laser radiation and the precursor is converted into a substance which forms the optical elements monolithically on the radiation transmission element (step S22b).
In a method for producing the optoelectronic device, first at least one semiconductor laser diode is provided (step S31), having an active zone for generating laser radiation. Also provided is a hermetic laser housing having a radiation exit window base element (step S32). The laser diode is then arranged in the laser housing (step S33) in such a way that in an operating state, the laser radiation of the laser diodes can exit via the radiation exit window base element. The application of the optical element or elements in step S34 to the radiation exit window base element takes place by exposing the radiation exit window base element, in step S34a, to an atmosphere with a precursor which can be induced to react in a chemical reaction by the laser radiation, and then, in step S34b, operating the laser diode, so that the chemical reaction is induced and the precursor is converted into a substance which forms the at least one optical element monolithically on the radiation exit window base element.
In the step S34a, an interior of the laser housing is preferably kept free from the precursor.
The at least one laser diode may in particular be a laser diode of one of the types described above. The substance may be a substance of the substances described above, more particularly silicon dioxide, in which case the precursor may be a volatile silicone.
The invention is elucidated more closely below in association with the appended figures, which schematically show:
The radiation guidance element 3 comprises a substance or consists of a substance which can be applied by means of the laser radiation 5 on the laser diode 2. The radiation guidance element 3 enables operation of the semiconductor laser 1 in normal ambient air, and is therefore a protective element.
Presently, moreover, the radiation guidance element 3 is shaped as a refractive lens. The radiation guidance element 3 is therefore a radiation outcoupling element 30 which has a radiation outcoupling face via which the laser radiation 5 can be delivered to an atmosphere.
As mentioned above, the radiation guidance element 3 comprises a substance which can be applied by means of the laser radiation 5 on the laser diode 2. A corresponding method is described in more detail below in association with
The method begins with the step S0 Start. In the step S1 the laser diode 2 is provided. Subsequently in the step S2 the radiation guidance element 3 is applied on the laser diode 2. The step S2 encompasses the component steps S2a and S2b. In the step S2a the laser diode 2 is exposed to an atmosphere with a precursor which can be induced to react in a chemical reaction by laser radiation 5. In the step S2b the laser diode is operated, so that the chemical reaction is induced and the precursor is converted into a substance which forms the radiation guidance element 3 in the radiation exit region 22 monolithically on the laser diode 2. The precursor may in particular be a silicone hydride or volatile silicone and the substance may be silicon dioxide. The method ends with the step SE End. Any hydrocarbons present are oxidized to CO2 by means of reaction with oxygen and are no longer available as reactants in the process.
The laser radiation 5 exits, deflected by 90°, at the top side of the prism 60. An arrangement of this kind may be used in particular as what is called a toplooker laser housing, i.e., as a semiconductor laser housing where the laser radiation 5 exits at the top side perpendicular to a basal face of the housing. With the basal face, the housing can be arranged on a support, such as a printed circuit board, for example, and contacted. The semiconductor laser 1 is arranged in this case on an assembly which extends parallel to the basal face, and emits the laser radiation 5 parallel to the basal face (perpendicular to the surface normal of the basal face).
With the present exemplary embodiment, moreover, the interspace between the prism 60 and the semiconductor laser diode 2 or the submount 42 is filled with a filling material 7, to provide said interspace with protection from contaminants, with sealing, and with mechanical stabilization.
Common to all of the exemplary embodiments described above is that the laser radiation 5, when coupled out into an atmosphere via one of the radiation outcoupling elements 30, 6, is widened in such a way that operation of the optoelectronic device in normal ambient air (e.g., terrestrial atmosphere at 300 kelvins) is possible.
A method for producing the semiconductor laser 1 according to the second and third exemplary embodiments is represented in
Subsequently, in the step S2, the radiation guidance element 3 is applied to the laser diode 2 in such a way that it monolithically connects the laser diode 2 to the radiation outcoupling element 6. The step S2 encompasses the component steps S2a and S2b. In the step S2a both the laser diode 2 and the radiation exit element 6 are exposed to the atmosphere with the precursor. The spacing between the radiation exit element 6 and the laser diode 2 was chosen in step S1b to be so low that in the step S2b of operation of the laser diode 2, the radiation guidance element 3 is formed in the radiation exit region 22 on the laser diode 2 and connects the laser diode 2 monolithically to the radiation guidance element 3. The method ends with the step SE End.
As a result, the radiation exit window 8a of
In this case, preferably only one side of the radiation exit window base element 80a is exposed to the precursor, so that the optical elements 31 are formed only on one side of the radiation exit window base element 80a. The element, for example, may be charged with a protective gas.
According to an alternative exemplary embodiment, in the case of the radiation exit window 8a according to
To produce the optoelectronic device 10, in principle, a corresponding radiation exit window 8a may be provided with the optical elements 31 and placed onto the laser housing 9, which already accommodates the laser diode 2 and the submount 4 and the prism 90, and aligned in such a way that the laser radiation 5 exits through the optical elements 31.
Preferably, however, the optoelectronic device 10 is produced according to the method represented in
In the subsequent method step S34, the optical elements 31 are applied on the radiation exit window base element 80a. The step S34 encompasses the component steps S34a and S34b. In the component step S34a, the radiation exit window base element 80a is exposed to an atmosphere with a precursor which can be induced to react in a chemical reaction by the laser radiation 5, and in the component step S34b, lastly, the laser diodes 2 are operated, so that the chemical reaction is induced and the precursor is converted into a substance which forms the optical elements 31 monolithically on the radiation exit window base element 80a. The method ends with the step SE End.
The method has been described in association with multiple laser diodes 2, but it is also possible to use a single laser diode 2, in which case-depending on the number of emission points—possibly only one optical element 31 is generated.
The methods described may be used in principle to generate all radiation guidance elements 3, more particularly optical elements 31, which can be realized by means of the beam shaping of the initiating laser radiation 5.
The interior 91 of the hermetic laser housing 9 is preferably kept free from the precursor, so that no optical elements are formed there.
With all of the methods described, the radiation exit window base element 80a or the laser diode 2 may be exposed to the precursor by means of a reaction chamber. In all exemplary embodiments, the precursor may in particular be one of the precursors described earlier on, and the substance may be one of the substances described earlier on.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 201 340.9 | Feb 2022 | DE | national |
The present application is a national stage entry from International Application No. PCT/EP2022/083179, filed on Nov. 24, 2022, published as International Publication No. WO 2023/151842 Al on Aug. 17, 2023, and claims priority to German Patent Application No. 10 2022 201 340.9, filed Feb. 9, 2022, the disclosures of all of which are hereby incorporated by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/083179 | 11/24/2022 | WO |
