Laser gyroscopes have traditionally included a laser block that comprises a ring shaped laser cavity filled with a gas lasing medium. High voltage anodes and cathodes in the laser block are energized to ionize the gas, and light generated by discharging of the gas is reflected around the ring shaped cavity by mirrors to generate a laser beam. However, such laser gyroscopes can suffer due to degradation of the gas lasing medium, and also require high voltage electronics and related infrastructure. Solid state lasers have been developed using Neodymium (Nd), which is one type of solid state LASER material that has desirable fluorescing properties, and may be doped with other materials to obtain other desired characteristics. Early Nd laser systems were typically pumped using tungsten filament lamps, and for that reason, the reliability of such lasers was an issue due to short lamp life as well as other reasons, such as the light not being well aligned with the axis of the laser beam path within the laser block.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for systems and methods for end pumped laser mirror stack assemblies.
The Embodiments of the present disclosure provide methods and systems for systems and methods for end pumped laser mirror stack assemblies and will be understood by reading and studying the following specification.
Systems and methods for end pumped laser mirror stack assemblies are provided. in one embodiment, an end pump mirror stack assembly for a laser resonator comprises: a pump light injection layer applied to a first surface of a transparent substrate, the pump light injection layer comprising at least one light generating optical emitter embedded within the pump light injection layer, wherein the pump light injection layer is configured to transmit a pump light having a first wavelength into the first surface of substrate; a multilayer thin-film mirror stack coupled to a second surface of the transparent substrate; a lasing material layer coupled to the second surface of the transparent substrate and positioned to receive the pump light, wherein the lasing material layer is doped with a dopant that generates a fluorescent light output at a second frequency when exposed to the pump light from the pump light injection layer; and an antireflective coating applied to the substrate, the first anti-reflective coating configured to pass light of the first wavelength.
Embodiments of the present disclosure can be more easily understood and further advantages and uses thereof more readily apparent, when considered in view of the description of the preferred embodiments and the following figures in which:
In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize features relevant to the present disclosure. Reference characters denote like elements throughout figures and text.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of specific illustrative embodiments in which the embodiments may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense.
Embodiments of the present disclosure provide systems and methods for end pumped laser mirror stack assemblies for use with closed path/ring laser gyroscope and other applications. As described in greater detail below, these embodiments employ stacking of a pump light source, mirror, substrates, mirror coatings, thin film lasing medium, and other materials, etc. into a single integrated stack. Such embodiments provide for direct optical pumping of the lasing medium) or another layer within the structure. The fluorescence generated by the optically pumped lasing medium could be located and aligned within the lasing path of a laser block assembly, with an efficient overlap with the optical path to achieve benefits over existing laser gyroscopes.
Optical emitters, such as light emitting diodes (LEDs), diode lasers, vertical-cavity surface-emitting laser, (VCSEL) lasers, edge mitting lasers, light-emitting coatings, as well as optional diffractive optical elements, may be integrated into the structure of the laser mirror stack for the purposed of pumping of the solid state laser materials, such as but not limited to Nd thin film material.
In the embodiment of
One or more light beams 120 created in the interior cavity ring 112 are repeatedly reflected around the interior cavity ring 112 by the mirror assemblies 114, 116 and 118 (either in the clockwise (CW) direction, counterclockwise (CCW) direction, or both) supporting gain to create lasing of the light beams 120 into laser light. In one embodiment, one of the other mirror assemblies (such as mirror assembly 116, for example) is used as a read-out device 130. The interior cavity ring 112 and the mirror assemblies 114, 116 and 118 thus form a closed laser resonator path. Is should be appreciated that in alternative implementations of the embodiments described herein, as opposed to the laser block sensor 110 comprising an interior resonator cavity that defines a ring path for the light beams 120 to follow, the interior resonator cavity of laser block sensor 110 may instead comprise a linear resonator.
The performance of ring laser gyroscope 100 is observed by coupling optical energy information from the interior cavity ring 112 to the read-out device 130 The readout device 130 inputs the optical energy and as a function of that optical energy provides an output of one or more voltage signals 132 to one or more processing elements 134. In some embodiments, the readout device 130 may comprise photodetectors. For example in some embodiments, differences in frequencies between counter-rotating laser beams within the interior cavity ring 112 may be determined from the voltage signals 132, and hence rotation information may be obtained. In addition to the rotation information, the readout device 130 may also provide a voltage signal correlated with laser intensity.
One of ordinary skill in the art after reading this specification would appreciate that
End pumped laser mirror stack assembly 200 comprises a multilayer thin-film mirror stack 210 deposited on a transparent substrate 205, a pump light injection layer 220 applied to the transparent substrate 205, and a fluorescing lasing material layer 230 (which may be applied to the multilayer thin-film mirror stack 210 or otherwise secured to the substrate 205). As discussed above, the path of a laser block sensor interior resonator cavity may be defined by the highly reflective multi-layer dielectric stacks (i.e., reflective at λ2) shown as mirror assemblies 114, 116 and 118 in
Pump light injection layer 220 is configured to transmit a beam of light of a first wavelength, λ1, (shown in
In some embodiments, pump light 222 is generated by one or more light generating optical emitters 221 embedded within the pump light injection layer 220. In alternate implementations, the optical emitters 221 may comprise one or more light emitting diodes (LEDs), an array of LEDs, one or more lasers or array of lasers such as vertical-cavity surface-emitting laser (VCSEL) lasers, edge emitting lasers, or one or more light-emitting coatings. In some embodiments, the pump light injection layer 220 may comprise an embedded or integrated multi-chip module with components on a carrier that is integrated within the pump light injection layer 220.
In operation, pump light 222 of wavelength λ1 is generated within the pump light injection layer 220 and directed to the lasing material layer 230. The lasing material layer 230 is doped with a dopant (for example, lasing material layer 230 may comprise a layer of Nd-doped silica) that generates a fluorescent light 232 at a second frequency, λ2, when exposed to the pump light 222 of wavelength λ1. For example, in one embodiment the pump light 222 generated by the pump light injection layer 220 has a wavelength λ1 of approximately 803 nm, which causes an Nd doped lasing material layer 230 to fluoresce an output of florescent light 232 having a wavelength λ2 of approximately 1050-1065 nm. The end pumped laser mirror stack assembly 200 outputs the fluorescent light 232 through its output end 212, which may be directed, for example, into the interior cavity ring 112 of the mirror stack end pumped laser gyroscope 100.
In one embodiment, the multilayer thin-film mirror stack 210 has a surface reflectivity that is highly reflective to any incoming light entering from output end 212 having a wavelength λ2. As the term is used herein, a surface or coating that is highly reflective has a reflectance of at least 99% for a specified wavelength. For example, in one embodiment, multilayer thin-film mirror stack 210 may comprises a dielectric mirror of alternating coatings of thin film dielectric layers having different refractivity characteristics that are selected to produce the highly reflective surface to light of wavelength λ2. Moreover, the refractivity characteristics of the dielectric layers may be tuned to optimize the reflectivity of light received at angle of incidence that would correspond to light expected to be received from the interior cavity ring 112. In contrast, the multilayer thin-film mirror stack 210 may at the same time be highly transmissive to light of wavelength λ1 so that the pump light 222 will pass through the multilayer thin-film mirror stack 210 to reach the lasing material layer 230 with little loss.
As shown in
With respect to wavelength λ1, reflection of any pump light 222 emerging from lasing material layer 230 back into the lasing material layer 230 enables multi passes of the pump light 222 through the lasing material which increases efficiency by permitting additional fluorescent light 232 to be produced from the pump light 222 already generated by pump light injection layer 220. With respect to wavelength λ2, having an optical coating layer with anti-reflective characteristics for light of wavelength λ2 reduce loss of efficiency caused by fluorescent light 232 failing to exit the end pumped laser mirror stack assembly 200 at output end 212, and also prevents losses due to scattering by ensuring that any laser light at λ2 received in from output end 212 passes completely to the multilayer thin-film mirror stack 210 before being reflected.
As such, when the end pumped laser mirror stack assembly 200 is used in conjunction with mirror stack end pumped laser gyroscope 100, light of wavelength λ2 is created in the interior cavity ring 112, traverses around interior cavity ring 112, and then is received back from interior cavity ring 112, and is reflected by the multilayer thin-film mirror stack 210 back into the interior cavity ring 112 with high efficiency, thus resulting in a high Q-factor (10{circumflex over ( )}8 or greater) laser block 110.
Because the pump light injection layer 220 is a rigidly integrated component of the end pumped laser mirror stack assembly 200, the fluorescent light 232 can exit from the end pumped laser mirror stack assembly 200 in alignment with the laser beam path defined within the interior cavity ring 112. That is, in some embodiments, the pump light injection layer 220 aligns the pump light 222 to produce fluorescent light 232 from the lasing material layer 230 that is aligned with the axis (that is, the plane) of the laser beam paths defined within the interior cavity ring 112.
Although Nd doped silica has been discussed above as an example lasing material for the lasing material layer 230, it should be understood that this material is mentioned for example purposes only, and that other solid or thin film lasing materials (for example, other rare-earth materials) may be used instead in silica, titania, or other glassy hosts (such as but not limited to oxide glasses, fluoride glasses, fluorosilicate glasses) for any of the embodiments described herein. It should also be understood that although the lasing material layer 230 is illustrated as a distinct layer, in other embodiments, lasing materials may be included, for example, within layers of the mirror stack or substrate 105,
For example, in
Example 1 includes an end pump mirror stack assembly for a laser resonator, the assembly comprising: a pump light injection layer applied to a first surface of a transparent substrate, the pump light injection layer comprising at least one light generating optical emitter embedded within the pump light injection layer, wherein the pump light injection layer is configured to transmit a pump light having a first wavelength into the first surface of substrate; a multilayer thin-film mirror stack coupled to a second surface of the transparent substrate; a lasing material layer coupled to the second surface of the transparent substrate and positioned to receive the pump light, wherein the lasing material layer is doped with a dopant that generates a fluorescent light output at a second frequency when exposed to the pump light from the pump light injection layer; and an antireflective coating applied to the substrate, the first anti-reflective coating configured to pass light of the first wavelength.
Example 2 include the assembly of claim 1, further comprising: an optical coating applied to the lasing material layer, the optical coating configured to be anti-reflective to light of the second wavelength, and highly-reflective to light of the first wavelength.
Example 3 include the assembly of any of claims 1-3, wherein the lasing material layer comprises a Neodymium doped thin film.
Example 3 include the assembly of any of claims 1-4, wherein the at least one light generating optical emitter comprises at least one of: a light emitting diode (LED), an array of LEDs, a vertical-cavity surface-emitting laser (VCSEL) laser; an edge emitting lasers, or a light-emitting coating.
Example 5 include the assembly of any of claims 1-5, wherein the pump light injection layer is coupled to the transparent substrate via a diffractive optical element layer.
Example 6 include the assembly of any of claims 1-6, wherein the pump light from the at least one light generating optical emitter is coupled into the first surface of the transparent substrate via a fiber optic medium.
Example 7 include the assembly of claim 6, wherein the pump light injection layer comprises an optical coupling element, wherein the pump light is coupled from the fiber optic medium into the transparent substrate via the optical coupling element.
Example 8 include the assembly of any of claims 1-7, wherein the pump light injection layer is a rigidly integrated component of the end pumped laser mirror stack assembly.
Example 9 include the assembly of any of claims 1-8, further comprising a piezoelectric driver, wherein the multilayer thin-film mirror stack is coupled to the substrate via the piezoelectric driver, and the piezoelectric driver is configured to mechanically oscillate the multilayer thin-film mirror stack.
Example 10 include the assembly of any of claim 9, wherein the pump light is directed to bypass the thin-film mirror stack.
Example 11 include the assembly of any of claim 9-10, wherein the multilayer thin-film mirror stack is inset such that at least a portion of the pump light from the pump light injection layer is applied to the lasing material layer without passing through the multilayer thin-film mirror stack.
Example 12 includes a mirror stack end pumped laser gyroscope, the gyroscope comprising: a laser block assembly having an interior resonator cavity therein; a readout device optically coupled to the laser block assembly that outputs one or more voltage signals; an end pumped laser mirror stack assembly coupled to the laser block assembly, wherein the end pumped laser mirror stack assembly creates one or more light beams in the interior resonator cavity; wherein the end pumped laser mirror stack assembly comprises: a pump light injection layer applied to a first surface of a transparent substrate, the pump light injection layer comprising at least one light generating optical emitter embedded within the pump light injection layer, wherein the pump light injection layer is configured to transmit a pump light having a first wavelength into the first surface of substrate; a multilayer thin-film mirror stack coupled to a second surface of the transparent substrate; a lasing material layer coupled to the second surface of the transparent substrate and positioned to receive the pump light, wherein the lasing material layer is doped with a dopant that generates a fluorescent light output at a second frequency when exposed to the pump light from the pump light injection layer, wherein the one or more light beams comprises the fluorescent light output; an antireflective coating applied to the substrate, the first anti-reflective coating configured to pass light of the first wavelength; an optical coating applied to the lasing material layer, the optical coating configured to be anti-reflective to light of the second wavelength, and highly-reflective to light of the first wavelength.
Example 13 include the gyroscope of claim 12, wherein interior resonator cavity of the laser block assembly comprises an interior cavity ring therein that defines a closed path laser beam path around the laser block assembly; and wherein the end pump mirror stack assembly is configured to direct a first portion of the fluorescent light output in a clockwise direction through the interior cavity ring, and a portion of the fluorescent light output in a counter-clockwise direction through the interior cavity ring.
Example 14 include the gyroscope of any of claims 12-13, wherein interior resonator cavity of the laser block assembly comprises an interior cavity ring therein that defines a closed path laser beam path around the laser block assembly; wherein the fluorescent light output is injected into the laser block assembly aligned with an axis of the closed path laser beam path of the interior cavity ring.
Example 15 include the gyroscope of any of claims 12-14, further comprising: an optical coating applied to the lasing material layer, the optical coating configured to be anti-reflective to light of the second wavelength, and highly-reflective to light of the first wavelength.
Example 16 include the gyroscope of any of claims 12-15, wherein the lasing material layer comprises a Neodymium doped thin film.
Example 17 include the gyroscope of any of claims 12-16, wherein the at least one light generating optical emitter comprises at least one of: a light emitting diode (LED), an array of LEDs, a vertical-cavity surface-emitting laser (VCSEL) laser, an edge emitting lasers, or a light-emitting coating.
Example 18 include the gyroscope of any of claims 12-17, wherein the pump light injection layer is coupled to the transparent substrate via a diffractive optical element layer.
Example 19 include the gyroscope of any of claims 12-18, further comprising a piezoelectric driver, wherein the multilayer thin-film mirror stack is coupled to the substrate via the piezoelectric driver, and the piezoelectric driver is configured to mechanically oscillate the multilayer thin-film mirror stack.
Example 20 include the assembly of claim 19, wherein the pump light does not pass through the thin-film mirror stack.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the presented embodiments. Therefore, it is manifestly intended that embodiments be limited only by the claims and the equivalents thereof.