CN220896064U - High-power distributed Bragg reflection laser - Google Patents
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- CN220896064U CN220896064U CN202322649803.7U CN202322649803U CN220896064U CN 220896064 U CN220896064 U CN 220896064U CN 202322649803 U CN202322649803 U CN 202322649803U CN 220896064 U CN220896064 U CN 220896064U
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Abstract
The utility model discloses a high-power distributed Bragg reflection laser which comprises a non-grating section/grating section, a lower electrode layer, a substrate, a lower waveguide cover layer, an active waveguide layer and an upper waveguide cover layer, wherein the non-grating section/grating section is longitudinally and sequentially arranged, and the lower electrode layer, the substrate, the lower waveguide cover layer, the active waveguide layer and the upper waveguide cover layer are transversely and sequentially arranged from bottom to top. The passive waveguide layer below the active layer has an optical field distributed mainly in the passive waveguide layer, reducing optical confinement of the ridge waveguide, thereby maintaining single mode behavior in a relatively wide ridge waveguide. Meanwhile, the distributed Bragg reflection laser structure is adopted, the cavity length can be effectively increased on the basis of generating a single longitudinal mode by utilizing the grating, so that the distribution of photon density in the cavity is shared, the occurrence of the phenomenon of space hole burning is effectively avoided, and meanwhile, the series resistance of the device is reduced, the heat dissipation area is increased, and the heat saturation output power is improved.
Description
Technical Field
The utility model relates to the technical field of semiconductor lasers, in particular to a high-power distributed Bragg reflection laser.
Background
The high-power semiconductor laser is widely applied to the fields of free space optical communication and laser radar for automatic driving, geographical information mapping and the like, and besides, the semiconductor laser is an important light source in the silicon-based photonics field, and a high-power laser is required to compensate on-chip loss. Currently, there are two main approaches for high power semiconductor lasers, namely distributed feedback (Distributed Feedback,DFB)(Y.Mao,Y.Cheng,B.Xu,R.Ji and Y.Li,et al.Record-High Power 1.55-μm Distributed Feedback Laser Diodes for Optical Communication[C]//Optical Fiber Communications Conference and Exhibition–OFC 2021) lasers and distributed bragg reflector (DistributedBragg Reflector, DBR) lasers.
A grating layer is added above or below the active region of the distributed feedback laser, and the length of the grating is consistent with the cavity length of the device. The grating realizes resonance selection of specific wavelength through periodic disturbance of physical parameters of the laser waveguide and the active region. It is often necessary to break the continuity of a uniform grating within a distributed feedback laser and introduce a lambda B/4 phase shift to relieve the mode degeneracy (Akiba S,Usami M,UtakaK.1.5μmλ/4-shifted InGaAsP/InP DFB laser[J].Journal of Lightwave Technology,1987,5(1):15664-1573), to achieve single mode lasing. However, typically such lasers are coated with an anti-reflection film on both ends, so that the output of the laser is at equal power on both ends, whereas typically only the optical energy output of one end is coupled to the optical fiber as externally available power, which results in half the output power loss of the laser. In addition, to obtain higher output power, the coupling coefficient of the grating is low so as to increase the saturation power of the laser, which results in that the threshold gain of the conventional phase shift distributed feedback laser is usually very high. There is a technological limitation on the distributed feedback laser in increasing the longitudinal waveguide size to achieve larger output power, and secondly, the product of the grating coupling coefficient and the length needs to be controlled to avoid the occurrence of space hole burning (Minwen Xiang,Yuanhao Zhang,et al.Wide-waveguide high-power low-RIN single-mode distributed feedback laser diodes for optical communicationp[J].Optics Express,2022,30(17),30187-30197.).
The distributed Bragg reflection laser also achieves optical feedback by incorporating Bragg gratings, but with grating regions on only two sides or one side of the laser cavity. By designing the structural parameters such as the length, the etching depth and the like of the grating, the optimal grating reflectivity and full width at half maximum can be obtained, and the single longitudinal mode lasing of the laser can be realized. In order to achieve high power output of the laser, a scheme (Li X,Liang L,Qin L,et al.Development ofa High-Power Surface Grating Tunable Distributed-Feedback Bragg Semiconductor LaserBased on Gain-Coupling Effect[J].Applied Sciences,2022,12(9):4498.), for introducing a tapered amplification region in the distributed bragg reflection laser can achieve high power output of the laser while maintaining single mode characteristics, but there are problems in that the beam is unstable and the output beam is difficult to be efficiently coupled into the optical fiber.
The distributed Bragg reflection laser structure can effectively improve the problem (Xun Li.Longitudinal spatial hole burning,its impact on laser operation,and suppression[J].Science Bulletin,2015,60(11):1045-1046.), of spatial hole burning, and the optical field in the laser is unevenly distributed along the longitudinal axis direction in the normal condition. Under the action of the unevenly distributed optical field and injected carriers, the carriers in the laser cavity also show uneven distribution along the longitudinal axis. Under the high injection condition, the space hole burning can introduce a non-uniform refractive index change in the cavity, and the refractive index change introduced by the grating is overlapped to weaken or lose the grating effect, so that the lasing mode is switched, jumped or oscillated in multiple longitudinal modes. The more unevenly distributed the optical field in the cavity, the more remarkable the spatial hole burning phenomenon. The lambda/4 phase shift grating distributed feedback laser has the advantages that the optical field is most concentrated at the center of the cavity, and the influence of the phenomenon is more obvious. The longitudinal length of the distributed Bragg reflection laser is not limited to increase, so that the photon density distribution in the cavity of the distributed Bragg reflection laser is more uniform relative to that of the distributed feedback laser, the phenomenon of space hole burning can be effectively avoided, and meanwhile, the series resistance of the device is reduced, the heat dissipation area is increased, and the heat saturation output power is improved. But at the same time the increase in ridge width requires strict control in order to avoid the generation of higher order modes. A distributed bragg reflector laser is typically coated on one side with a highly reflective film, while a lower threshold gain is more readily achieved by controlling the reflectivity of the grating.
In combination with the above, the problems mainly faced by the current high-power semiconductor laser can be divided into the problems of high-power implementation and mode control, and meanwhile, instability caused by phenomena such as space hole burning needs to be considered.
Disclosure of utility model
The present utility model is directed to a high power distributed bragg reflector laser that solves the above-mentioned problems of the prior art.
In order to achieve the above purpose, the present utility model provides a high-power distributed bragg reflection laser, which adopts the following technical scheme:
A high-power distributed Bragg reflection laser comprises a non-grating section, a lower electrode layer, a substrate, a lower waveguide cover layer, a passive waveguide layer and an upper waveguide cover layer which are sequentially arranged longitudinally and horizontally from bottom to top.
Preferably, an active layer and an active waveguide layer are sequentially arranged between the passive waveguide layer and the upper waveguide cover layer from bottom to top, and the active waveguide layer is engraved with a Bragg grating; the grating section is carved with Bragg grating, one end of the non-grating section far away from the grating section is provided with a high reflection film, and one end of the grating section far away from the non-grating section is provided with an anti-reflection film.
Preferably, the upper waveguide cover layer comprises an unetched layer and a ridge layer which are sequentially arranged from bottom to top; the substrate, the lower waveguide cover layer, the non-source waveguide layer, the unetched layer and the ridge layer form a ridge waveguide structure.
Preferably, the active layer includes a lower respective confinement layer, a quantum well, and an upper respective confinement layer sequentially disposed from bottom to top.
Preferably, the upper end of the upper waveguide cover layer is provided with an ohmic contact layer and an upper electrode layer in sequence from bottom to top.
Preferably, the optical field of the active waveguide layer has a bragg grating coupling coefficient with the active waveguide layer of less than 30cm -1.
Preferably, the bragg grating of the active waveguide layer is a first-order bragg grating.
Preferably, the period of the bragg grating is Λ=mλ B/2neff, where λ B and m are the bragg wavelength and the number of stages corresponding to the grating, and n eff is the effective refractive index of the grating segment waveguide.
Preferably, the lower waveguide cover layer is doped with N type, and a highly doped N ohmic contact layer is arranged between the lower waveguide cover layer and the substrate; the upper waveguide cover layer is doped in a P type, and a highly doped P ohmic contact layer is arranged at the upper end of the upper waveguide cover layer; the upper waveguide cover layer, the active layer and the lower waveguide cover layer together form a P-i-N structure.
Preferably, the longitudinal direction is the length direction of the laser, and the transverse direction is the growth direction of the epitaxial wafer of the laser.
The beneficial effects of the utility model are as follows: the passive waveguide layer below the active layer has an optical field distributed mainly in the passive waveguide layer, reducing optical confinement of the ridge waveguide, thereby maintaining single mode behavior in a relatively wide ridge waveguide. Meanwhile, the distributed Bragg reflection laser structure is adopted, the cavity length can be effectively increased on the basis of generating a single longitudinal mode by utilizing the grating, so that the distribution of photon density in the cavity is shared, the occurrence of the phenomenon of space hole burning is effectively avoided, and meanwhile, the series resistance of the device is reduced, the heat dissipation area is increased, and the heat saturation output power is improved.
Drawings
In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. Like elements or portions are generally identified by like reference numerals throughout the several figures. In the drawings, elements or portions thereof are not necessarily drawn to scale.
Fig. 1 shows a schematic structure of a high-power distributed bragg reflector laser according to an embodiment of the present utility model.
Fig. 2 shows a longitudinal cross-sectional view of a high power distributed bragg reflector laser in accordance with an embodiment of the present utility model.
Fig. 3 shows a carrier concentration profile within the cavity of a high power distributed bragg reflector laser in accordance with an embodiment of the present utility model.
Fig. 4 shows a photon concentration profile in a cavity of a high power distributed bragg reflector laser in accordance with an embodiment of the present utility model.
Fig. 5 shows a graph of output optical power versus input current for a high power distributed bragg reflector laser in accordance with an embodiment of the present utility model.
The low-power semiconductor device comprises a lower electrode layer-1, an ohmic contact layer-2, a lower waveguide cover layer-3, an passive waveguide layer-4, a lower limiting layer-5, a quantum well-6, an upper limiting layer-7, an active layer-8, an active waveguide layer-9, an unetched layer-10, a ridge layer-11, an upper waveguide cover layer-12, a high-reflection film-13, an antireflection film-14, a non-grating section-15, a grating section-16 and an upper electrode layer-18.
Detailed Description
Other advantages and effects of the present utility model will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present utility model with reference to specific examples. The utility model may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present utility model. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.
In the description of the present utility model, unless otherwise indicated, the meaning of "a plurality" is two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front," "rear," "head," "tail," and the like are used as an orientation or positional relationship based on that shown in the drawings, merely to facilitate description of the utility model and to simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the utility model. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present utility model, it should be noted that, unless explicitly specified and limited otherwise, the terms "connected," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in the present utility model will be understood in specific cases by those of ordinary skill in the art.
The following describes in further detail the embodiments of the present utility model with reference to the drawings and examples.
The embodiment of the utility model provides a high-power distributed Bragg reflection laser, which is shown in figures 1-2, and comprises a laser, wherein the laser longitudinally and sequentially comprises a non-grating section 15 and a grating section 16, and the laser is transversely and sequentially provided with a lower electrode layer 1, a substrate, a lower waveguide cover layer 3, a passive waveguide layer 4 and an upper waveguide cover layer 12 from bottom to top; an active layer 8 and an active waveguide layer 9 are sequentially arranged between the passive waveguide layer 4 and the upper waveguide cover layer 12 of the grating section 16 from bottom to top, and a Bragg grating is engraved on the active waveguide layer 9; the end of the non-grating section 15, which is far away from the grating section 16, is provided with a high-reflection film, and the end of the grating section 16, which is far away from the non-grating section 15, is provided with a high-reflection film anti-reflection film.
In some embodiments, in order to make the ohmic contact layer 2 possess enough carriers and ensure the normal operation of the laser, the ohmic contact layer 2 and the upper waveguide cap layer 12 are heavily doped with P-type, the doping concentration range is 10 19～1020cm-3, the lower waveguide cap layer 3 is doped with N-type, the active layer 8 is not doped, and the upper waveguide cap layer 12, the active layer 8 and the lower waveguide cap layer 3 together form a P-i-N structure.
In some embodiments, the active layer 8 contains one or more quantum wells 6, and the quantum wells 6 may be bulk materials, quantum wires, and quantum dots.
In some embodiments, to ensure that the laser has sufficient single mode characteristics and that the bragg wavelength corresponding to the grating corresponds to the resonant wavelength of the resonant cavity, a portion of the grating section 16 is fabricated in the active waveguide layer 9.
In some embodiments, to reduce the effect of the reflection of the etched interface, an etched interface that is tilted horizontally may be used to avoid the effect of the reflection of the etched interface on the performance of the laser.
In some embodiments, there may be a highly doped N ohmic contact layer 2 between the lower waveguide cap layer 3 and the substrate, and a highly doped P ohmic contact layer 2 on the upper waveguide cap layer 12.
In some embodiments, the grating segments 16 are used for the output end face.
In some embodiments, the coupling coefficient of the grating segment 16 grating is adjusted by adjusting parameters such as the etch depth of the grating segment 16 grating, the refractive index of the active waveguide layer 9 material, and the distance of the active waveguide layer 9 to the active layer 8.
In some embodiments, the left and right sides of fig. 1 and 2 are all covered according to the description; the non-grating section 15 is located at the left end of the laser in the length direction and the grating section 16 is located at the right end of the laser in the length direction.
The following examples of the present utility model will demonstrate the feasibility and advancement of the utility model in conjunction with specific experiments.
Fig. 3 and 4 show the carrier concentration and the photon concentration distribution in the cavity at the injection current of 800mA according to a specific embodiment of the high-power distributed bragg reflector laser of the present utility model, and it can be seen that the distribution of photons and carriers in the laser cavity is uneven according to this embodiment. Wherein the photon concentration is highest at the junction of the non-grating section and the grating section, and the carrier concentration is lowest. And the photon density of the grating area is in a descending trend along with the increment of the longitudinal coordinate, the photon density valley value is appeared at a position close to the output end face under the influence of photon output, and the photon density of the non-grating area is in a gentle descending trend along with the reduction of the longitudinal coordinate. The phenomenon can be explained by a carrier velocity equation, and under constant current, the carrier generation rate is constant, and the carrier density is smaller as the carrier consumption rate is larger in the region with higher photon density.
Fig. 5 is a graph showing a relationship between output power and input current according to a specific embodiment of a high-power distributed bragg reflector laser according to the present utility model, and the present embodiment can find that the threshold current of the laser is about 88mA and the slope efficiency is 0.28mW/mA, so that the laser can achieve the performance of low threshold and high slope efficiency.
According to the utility model, the passive waveguide layer structure is introduced below the active layer, so that the limitation of the ridge waveguide on the mode can be reduced, the single-mode behavior is kept under the condition of wide waveguide, meanwhile, the distributed Bragg reflection laser structure is adopted, only the grating section 16 is carved with a grating, and the single longitudinal mode output of the laser can be controlled by designing the grating structure. The structure can effectively avoid the occurrence of the phenomenon of space hole burning by increasing the cavity length of the laser, and simultaneously reduce the series resistance of the device and increase the heat dissipation area so as to improve the heat saturation output power.
The above embodiments are only for illustrating the present utility model, not for limiting the present utility model, and various changes and modifications may be made by one of ordinary skill in the relevant art without departing from the spirit and scope of the present utility model, and therefore, all equivalent technical solutions are also within the scope of the present utility model, and the scope of the present utility model is defined by the claims.
Claims (9)
1. A high power distributed bragg reflector laser, characterized by: the non-grating-type light source device comprises a non-grating section (15), a grating section (16), a lower electrode layer (1), a substrate, a lower waveguide cover layer (3), an passive waveguide layer (4) and an upper waveguide cover layer (12) which are sequentially arranged longitudinally and horizontally from bottom to top.
2. A high power distributed bragg reflector laser as claimed in claim 1, wherein: an active layer (8) and an active waveguide layer (9) are sequentially arranged between the passive waveguide layer (4) and the upper waveguide cover layer (12) from bottom to top, and the active waveguide layer (9) is engraved with a Bragg grating; the optical grating comprises a grating section (16), wherein Bragg gratings are engraved on the grating section (16), a high-reflection film (13) is arranged at one end, far away from the grating section (16), of the non-grating section (15), and an antireflection film (14) is arranged at one end, far away from the non-grating section (15), of the grating section (16).
3. A high power distributed bragg reflector laser as claimed in claim 1, wherein: the upper waveguide cover layer (12) comprises an unetched layer (10) and a ridge layer (11) which are sequentially arranged from bottom to top; the substrate, the lower waveguide cover layer (3), the passive waveguide layer (4), the unetched layer (10) and the ridge layer (11) form a ridge waveguide structure.
4. A high power distributed bragg reflector laser as claimed in claim 2, wherein: the active layer (8) comprises a lower limiting layer (5), a quantum well (6) and an upper limiting layer (7) which are sequentially arranged from bottom to top.
5. A high power distributed bragg reflector laser as claimed in claim 1, wherein: the upper end of the upper waveguide cover layer (12) is sequentially provided with an ohmic contact layer (2) and an upper electrode layer (18) from bottom to top.
6. A high power distributed bragg reflector laser as claimed in claim 2, wherein: the optical field of the active waveguide layer (9) has a Bragg grating coupling coefficient with the active waveguide layer (9) of less than 30cm -1.
7. A high power distributed bragg reflector laser as in claim 6 wherein: the Bragg grating of the active waveguide layer (9) is a first-order Bragg grating.
8. A high power distributed bragg reflector laser as in claim 7 wherein: the period of the Bragg grating is lambada=mlambada B/2neff, wherein lambada B and m are Bragg wavelength and progression corresponding to the grating respectively, and n eff is the effective refractive index of the grating segment (16) waveguide.
9. A high power distributed bragg reflector laser as claimed in claim 1, wherein: the lower waveguide cover layer (3) is doped in an N type, and a high-doped N ohmic contact layer (2) is arranged between the lower waveguide cover layer (3) and the substrate; the upper waveguide cover layer (12) is doped in a P type, and a highly doped P ohmic contact layer (2) is arranged at the upper end of the upper waveguide cover layer (12); the upper waveguide cover layer (12), the active layer (8) and the lower waveguide cover layer (3) together form a P-i-N structure.
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