CN116316051A - Surface emitting laser - Google Patents

Surface emitting laser Download PDF

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Publication number
CN116316051A
CN116316051A CN202310032186.8A CN202310032186A CN116316051A CN 116316051 A CN116316051 A CN 116316051A CN 202310032186 A CN202310032186 A CN 202310032186A CN 116316051 A CN116316051 A CN 116316051A
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China
Prior art keywords
electrode
emitting laser
insulating pattern
layer
substrate
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CN202310032186.8A
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Chinese (zh)
Inventor
张炜阳
张�成
刘嵩
翁玮呈
梁栋
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Vertilite Co Ltd
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Vertilite Co Ltd
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Priority to CN202310032186.8A priority Critical patent/CN116316051A/en
Publication of CN116316051A publication Critical patent/CN116316051A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H01S5/0425—Electrodes, e.g. characterised by the structure
    • H01S5/04254—Electrodes, e.g. characterised by the structure characterised by the shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
    • H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention discloses a surface emitting laser, comprising: a substrate; an epitaxial layer located on one side of the substrate; the epitaxial layer is used for forming a light-emitting platform, and the light-emitting platform comprises at least one active layer; a first electrode located on a side of the epitaxial layer away from the substrate; the second electrode is positioned on one side of the substrate away from the epitaxial layer; or, the substrate is positioned on one side close to the epitaxial layer and surrounds the light-emitting platform; wherein the first electrode is a grid electrode formed by a plurality of conductive grids; each conductive grid comprises an insulating pattern with a corresponding filling coefficient; the insulating pattern is used for adjusting carrier densities of different positions of the active layer; the filling factor of the insulating pattern is the area ratio of the insulating pattern to the conductive grid. The control of carrier density distribution is realized, and then the control of specific mode light excitation and polarization is realized.

Description

Surface emitting laser
Technical Field
The embodiment of the invention relates to the technical field of lasers, in particular to a surface emitting laser.
Background
The surface emitting laser is mainly VCSEL (Vertical Cavity Surface Emitting Laser ), has the advantages of small volume, round output light spot, single longitudinal mode output, small threshold current, low price, easy integration into a large-area array and the like, and is widely applied to the fields of optical communication, optical interconnection, optical storage and the like.
However, in the conventional VCSEL device, the electrode into which the current is injected is ring-shaped, control over carrier density distribution cannot be achieved, and gaussian distribution of carrier density distribution cannot be easily achieved; with the increase of the injection current, the Gaussian beam is degraded, so that the far-field light spots form hollow distribution, the orthogonal polarization suppression ratio (Orthogonal polarization suppression ratio, OPSR) is reduced, and the wavelength consistency is reduced.
Disclosure of Invention
The embodiment of the invention provides a surface emitting laser to realize the control of carrier density distribution, and further realize the control of specific mode light excitation and polarization.
The embodiment of the invention provides a surface emitting laser, which comprises the following components:
a substrate;
an epitaxial layer located on one side of the substrate; the epitaxial layer is used for forming a light-emitting platform, and the light-emitting platform comprises at least one active layer;
a first electrode located on a side of the epitaxial layer away from the substrate;
a second electrode located on a side of the substrate away from the epitaxial layer; or, the light emitting platform is positioned on one side of the substrate close to the epitaxial layer and surrounds the light emitting platform;
wherein the first electrode is a grid electrode formed by a plurality of conductive grids; each conductive grid comprises an insulating pattern with a corresponding filling coefficient; the insulating pattern is used for adjusting carrier densities of different positions of the active layer; the filling factor of the insulating pattern is the area ratio of the insulating pattern to the conductive mesh.
Optionally, the shape of the conductive mesh comprises a hexagon; the patterns of the first electrode are formed by splicing hexagons with the same area;
the shape of the insulating pattern includes at least one of a hexagon and a circle.
Optionally, the light emitting direction is a direction in which the active layer points to the substrate;
the second electrode comprises a first opening, and the area of the first opening is larger than or equal to the area of the light emergent hole;
the vertical projection of the first electrode on the second electrode is positioned in the area of the first opening.
Optionally, the filling factor of the insulating pattern increases stepwise, linearly or non-linearly along the direction of the center pointing edge of the first electrode.
Optionally, the first electrode includes a first fully conductive region, the first fully conductive region being located in a central region of the first electrode; in the first fully conductive region, the filling factor of the insulating pattern inside the conductive mesh is equal to zero.
Optionally, the first electrode is in an axisymmetric structure, and the direction of the symmetry axis of the first electrode is parallel to the fixed crystal direction;
the filling coefficient of the insulating pattern inside the conductive grid is smaller than a first preset value between a first boundary and a second boundary which are at the same distance from the symmetry axis and are parallel to the symmetry axis; the filling coefficient of the conductive grid internal insulation pattern on the side of the first boundary away from the second boundary and the filling coefficient of the conductive grid internal insulation pattern on the side of the second boundary away from the first boundary are larger than the first preset value.
Optionally, between the first boundary and the second boundary, along a direction in which a center of the first electrode points to an edge, a filling factor of the insulating pattern increases stepwise, linearly, or non-linearly.
Optionally, the first electrode comprises a plurality of second fully conductive regions; in the second fully conductive region, the filling coefficient of the insulating pattern inside the conductive mesh is equal to zero;
the first electrode includes a plurality of symmetry axes; the second fully conductive areas are positioned at the edges of the different sides of the first electrode and are correspondingly arranged on one symmetry axis; and the configuration of different positions of the second completely conductive region is used for forming the lasing of a preset high-order mode.
Optionally, the epitaxial layer further includes at least one oxide layer, and the oxide layer includes a second opening; the oxide layer is used for limiting the flow direction of carriers.
Optionally, the epitaxial layer further includes an upper bragg reflection layer and a lower bragg reflection layer, and the lower bragg reflection layer is located between the active layer and the substrate; the upper Bragg reflection layer is positioned on one side of the active layer away from the substrate; the surface-emitting laser is of a vertical cavity surface-emitting laser type;
or, the epitaxial layer further comprises a two-dimensional photonic crystal layer, and the two-dimensional photonic crystal layer is positioned on one side of the active layer; the surface emitting laser is of a photonic crystal surface emitting laser type;
or, the epitaxial layer further comprises a widirac vortex structure, and the widirac vortex structure is located on one side of the active layer; the type of the surface emitting laser is a topological cavity surface emitting laser.
The embodiment of the invention provides a surface emitting laser, which comprises the following components: a substrate; an epitaxial layer located on one side of the substrate; wherein the epitaxial layer comprises at least one active layer; a first electrode located on a side of the epitaxial layer away from the substrate; the second electrode is positioned on one side of the substrate away from the epitaxial layer; or the substrate is positioned on one side close to the epitaxial layer and is arranged around the epitaxial layer; wherein the first electrode is a metal grid electrode; each conductive grid comprises an insulating pattern with a corresponding filling coefficient; the insulating pattern is used for adjusting carrier densities of different positions of the active layer; the filling factor of the insulating pattern is the area ratio of the insulating pattern to the conductive grid. The control of carrier density distribution is realized through changing the filling coefficient of the metal grid electrode, and then the functions of specific mode light excitation, polarization control and the like are realized. Compared with the annular electrode, the current injection along the radial direction is more uniform, and the carrier density distribution of Gaussian distribution is easier to realize.
It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the invention or to delineate the scope of the invention. Other features of the present invention will become apparent from the description that follows.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic cross-sectional structure of a surface-emitting laser according to an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of another surface-emitting laser according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of another surface-emitting laser according to an embodiment of the present invention;
FIG. 4 is a schematic top view of a first electrode and a second electrode according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a first electrode according to an embodiment of the present invention;
FIG. 6 is a schematic view of another first electrode according to an embodiment of the present invention;
FIG. 7 is a schematic view of another first electrode according to an embodiment of the present invention;
FIG. 8 is a schematic view of another first electrode according to an embodiment of the present invention;
FIG. 9 is a schematic view of another first electrode according to an embodiment of the present invention;
FIG. 10 is a schematic view of another first electrode according to an embodiment of the present invention;
FIG. 11 is a schematic view of another first electrode according to an embodiment of the present invention;
fig. 12 is a schematic structural diagram of another first electrode according to an embodiment of the present invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
An embodiment of the present invention provides a surface-emitting laser, fig. 1 is a schematic cross-sectional structure of the surface-emitting laser provided by the embodiment of the present invention, fig. 2 is a schematic cross-sectional structure of another surface-emitting laser provided by the embodiment of the present invention, fig. 3 is a schematic cross-sectional structure of another surface-emitting laser provided by the embodiment of the present invention, and fig. 4 is a schematic top view of a first electrode and a second electrode provided by the embodiment of the present invention; fig. 5 is a schematic structural diagram of a first electrode according to an embodiment of the present invention; referring to fig. 1 to 5, the surface emitting laser includes:
a substrate 10;
an epitaxial layer located on one side of the substrate 10; wherein the epitaxial layer is used for forming a light emitting platform 20, and the light emitting platform 20 comprises at least one active layer 22;
a first electrode 30 located on a side of the epitaxial layer remote from the substrate 10;
a second electrode 40 located on a side of the substrate 10 remote from the epitaxial layer; or, on the side of the substrate 10 close to the epitaxial layer, around the light-emitting stage 20;
wherein the first electrode 30 is a grid electrode; each conductive mesh 31 includes therein an insulation pattern 311 of a corresponding fill factor; the insulating pattern 311 is used to adjust carrier densities at different positions of the active layer 22; the filling factor of the insulating pattern 311 is the area ratio of the insulating pattern 311 to the conductive mesh 31.
Specifically, the substrate 10 may be any material suitable for forming a laser, and the material of the substrate 10 may be GaAs or Si, or the like. The epitaxial layer is located on one side of the substrate 10; wherein the epitaxial layer comprises at least one active layer 22; the active layer 22 is used to provide gain. When the number of active layers 22 is plural, two adjacent active layers 22 are connected by a tunnel junction. Increasing the number of active layers 22 can realize the doubling of the light output of the surface-emitting laser. The active layer 22 may include a quantum well and confinement layers on both sides of the quantum well.
The first electrode 30 and the second electrode 40 are used to supply power to the active layer 22. Referring to fig. 1 and 3, when the first electrode 30 is located on a side of the epitaxial layer away from the substrate 10 and the second electrode 40 is located on a side of the substrate 10 away from the epitaxial layer, the first electrode 30 and the second electrode 40 are located on opposite sides of the substrate 10, and the surface emitting laser is a PN hetero-surface laser. Referring to fig. 2, when the first electrode 30 is located on a side of the epitaxial layer away from the substrate 10, and the second electrode 40 is located on a side of the substrate 10 close to the epitaxial layer and is disposed around the light emitting stage, the first electrode 30 and the second electrode 40 are located on the same side of the substrate 10, and the surface emitting laser is a PN coplanar laser. In addition, in embodiments of the present invention, the surface emitting laser may be a Vertical Cavity Surface Emitting Laser (VCSEL), a photonic crystal surface emitting laser (Photonic Crystal Surface Emitting Laser, PCSEL), or a topological cavity surface emitting laser (Topological Cavity Surface Emitting Laser, TCSEL).
Referring to fig. 1 and 2, when the surface-emitting laser is of the vertical cavity surface-emitting laser (VCSEL) type, the epitaxial layer further includes an upper bragg reflective layer 23 and a lower bragg reflective layer 21, the lower bragg reflective layer 21 being located between the active layer 22 and the substrate 10; the upper bragg reflective layer 23 is located on the side of the active layer 22 remote from the substrate 10. Each period of the lower bragg reflection layer 21 is composed of a first refractive index material having an optical thickness of an odd multiple of the quarter lasing wavelength and a second refractive index material having an optical thickness of an odd multiple of the quarter lasing wavelength. The material of the lower bragg reflection layer 21 may be a dielectric material, such as silicon oxide, silicon nitride, or the like; or may be a III-V semiconductor material such as an arsenide, phosphide, nitride, or the like. Each period of the upper bragg reflection layer 23 is composed of a first refractive index material having an optical thickness of an odd multiple of the quarter lasing wavelength and a second refractive index material having an optical thickness of an odd multiple of the quarter lasing wavelength. The material of the upper bragg reflection layer 23 may be a dielectric material, such as silicon oxide, silicon nitride, etc.; or may be a III-V semiconductor material such as an arsenide, phosphide, nitride, or the like. The reflectivity is adjusted by the upper and lower bragg reflection layers 23 and 21 to provide the maximized output optical power.
Referring to fig. 3, when the surface emitting laser is of the Photonic Crystal Surface Emitting Laser (PCSEL) type, the epitaxial layer further includes a two-dimensional photonic crystal layer 60, and the two-dimensional photonic crystal layer 60 is located on one side of the active layer 22 and is spaced apart from the active layer 22 by a spacer layer 61. The two-dimensional photonic crystal layer 60, the spacer layer 61, and the active layer 22 are located between the first cladding layer 211 and the second cladding layer 231. Although the first cladding layer 211 and the second cladding layer 231 are not essential components in the present invention, they have an effect of connecting the first electrode 30 and the active layer 22 and the second electrode 40 and the two-dimensional photonic crystal layer 60 and facilitating injection of current from the first electrode 30 and the second electrode 40 to the active layer 22. To perform these functions, an N-type semiconductor may be used as a material of the first cladding layer 211, and a P-type semiconductor may be used as a material of the second cladding layer 231. First, theOne cladding layer 211 may be the lower bragg reflective layer 21 and the second cladding layer 231 may be the upper bragg reflective layer 23. The two-dimensional photonic crystal layer 60 is formed by etching a photonic crystal layer host material to form circular air holes, or a material having a different refractive index from the photonic crystal layer host material may be filled in the circular air holes. Illustratively, the bulk material of the photonic crystal layer has a refractive index n 1 The refractive index of air is n 2 Etching to form periodically arranged etching holes in the main material of the photon crystal layer, wherein if the area of the periodically arranged etching holes is regarded as an equivalent uniform medium, the refractive index of the medium is between the refractive index n of the main material of the photon crystal layer 1 Refractive index n with air 2 Between them. In the two-dimensional photonic crystal surface-emitting laser, only light of a given wavelength corresponding to the period of the differential refractive index region is amplified to generate laser oscillation, and emitted as a laser beam in a direction perpendicular to the two-dimensional photonic crystal, among light generated by the active layer 22 by injecting current into the active layer 22; the region with different refractive index is a region in which etched holes are periodically arranged in the two-dimensional photonic crystal layer 60. Since the two-dimensional photonic crystal surface-emitting laser emits light (surface light) from a certain range in the two-dimensional photonic crystal, the emission area is larger than that of the end-surface-emitting semiconductor laser, and thus the light output can be easily improved and the diffusion angle can be reduced.
When the surface emitting laser is a Topological Cavity Surface Emitting Laser (TCSEL), the two-dimensional photonic crystal layer 60 includes a vidira vortex structure that is located on one side of the active layer 22. The topological optical cavity is designed by vortex modulation Dirac photon crystal. The cavity can realize excellent characteristics of single mode, random multiple degeneracy modes, maximum free spectrum range, small far field divergence angle, vector light field output, mode area adjustable from micrometer to millimeter, compatibility of various substrates 10 and the like.
In fig. 4, the outline of the first electrode 30 is illustrated as a circle, and the outline of the second electrode 40 is illustrated as a circular ring. In other embodiments, the contour of the first electrode 30 may be square and the contour of the second electrode 40 may be square and ring-shaped. In the embodiment of the present invention, the light emitting direction of the laser may be the direction in which the active layer 22 points to the substrate 10, i.e. the surface emitting laser emits back light; the annular second electrode 40 includes a first opening, the area of the first opening is greater than or equal to the area of the light emitting hole, the vertical projection of the first electrode 30 on the second electrode 40 is located in the area of the first opening, there is no overlap, and the contour of the first electrode 30 should be smaller than the contour of the second electrode 40. If the light emitting direction of the laser is the direction in which the active layer 22 is directed to the first electrode 30, the material of the first electrode 30 needs to have transparency.
Referring to fig. 5, the first electrode 30 may be a metal mesh electrode; each conductive mesh 31 includes therein an insulation pattern 311 of a corresponding fill factor; the insulating pattern 311 is used to adjust carrier densities at different positions of the active layer 22; the filling factor of the insulating pattern 311 can be understood as the area ratio of the insulating pattern 311 to the conductive grid 31. By increasing the fill factor in a region, the total area of the insulating pattern 311 in the region can be increased, and the total area of the conductive region in the region can be reduced, thereby reducing the conductivity of the region, and further reducing the carrier density in the region corresponding to the active layer 22. By decreasing the fill factor in a region, the total area of the insulating pattern 311 in the region can be decreased, and the total area of the conductive region in the region can be increased, thereby increasing the conductivity of the region, and further increasing the carrier density in the region corresponding to the active layer 22. The control of carrier density distribution can be realized through adjusting the filling coefficient of the metal grid electrode, so that the functions of specific mode light excitation, polarization control and the like are realized. Compared with the annular first electrode, the current injection along the radial direction is more uniform, and the carrier density distribution of Gaussian distribution is easier to realize.
In the prior art, for large aperture VCSELs, carrier density is concentrated at the oxide aperture edge. Higher order modes with energy distribution closer to the edges are more easily excited than the fundamental mode with near gaussian distribution, resulting in far field spots that appear annular. In the embodiment of the invention, the density distribution of carriers can be controlled by changing the filling coefficient of the metal grid electrode, so that the functions of specific mode light excitation, polarization control and the like can be realized. For example, the filling coefficient of the insulating pattern 311 may be gradually increased along the radial direction from the center of the circle to the outside, so that the carrier distribution of maximum density generated in the middle region of the active region may be satisfied, which approximates to gaussian distribution. In this way, the gain of the fundamental mode can be higher, the gain of the higher-order mode is lower due to weaker carrier distribution at the edge, and the problem of reducing the orthogonal polarization suppression ratio due to the higher-order mode can be improved.
The surface emitting laser provided by the embodiment of the invention comprises: a substrate; an epitaxial layer located on one side of the substrate; wherein the epitaxial layer comprises at least one active layer; a first electrode located on a side of the epitaxial layer away from the substrate; the second electrode is positioned on one side of the substrate away from the epitaxial layer; or, the light emitting stage is disposed around the light emitting stage in the epitaxial layer on a side of the substrate adjacent to the epitaxial layer. Wherein the first electrode is a metal grid electrode; each conductive grid comprises an insulating pattern with a corresponding filling coefficient; the insulating pattern is used for adjusting carrier densities of different positions of the active region; the filling factor of the insulating pattern is the area ratio of the insulating pattern to the conductive grid. The control of carrier density distribution is realized through changing the filling coefficient of the metal grid electrode, and then the functions of specific mode light excitation, polarization control and the like are realized. Compared with the annular electrode, the current injection along the radial direction is more uniform, and the carrier density distribution of Gaussian distribution is easier to realize.
As an alternative to one embodiment of the invention, referring to fig. 5, the shape of the conductive mesh 31 comprises a hexagon; the pattern of the first electrode 30 is formed by hexagonal concatenation with the same area; the shape of the insulating pattern 311 includes at least one of a hexagon and a circle.
It will be appreciated that the first electrode 30 comprises a plurality of hexagonal conductive grids 31, and that the pattern of the first electrode 30 is formed by a concatenation of hexagons of equal area. As shown in fig. 5, the shape of the first electrode 30 may be circular. The hexagonal conductive mesh 31 is arranged around a hexagonal conductive mesh 31 at the center, and a plurality of circles of hexagonal conductive meshes 31 are sequentially arranged around the hexagonal conductive mesh 31 at the center, thereby forming a "honeycomb-shaped" mesh electrode. In the conductive mesh 31, the width of the conductive mesh line is determined according to the filling factor of the insulating pattern 311.
When the filling factor of the insulating pattern 311 in a conductive mesh 31 is zero, the conductive mesh 31 is a monolithic conductive layer. As the area of the insulating pattern 311 in the conductive mesh 31 increases gradually, the filling factor of the insulating pattern 311 in the conductive mesh 31 increases gradually, and the width of the conductive mesh line decreases gradually. The filling factor of the insulating pattern 311 in the conductive mesh 31 increases to 100%, and the conductive mesh 31 is entirely filled with the insulating pattern 311. When the filling coefficients of two adjacent conductive grids 31 are 100%, the two conductive grids 31 are connected to form a whole insulation region. In the embodiment of the present invention, the filling coefficient of the insulating pattern 311 in each conductive grid 31 is set to be less than 100%, so that each conductive grid 31 has a conductive grid 31 line with a certain width, thereby ensuring the conductivity of each conductive grid 31.
The position of the insulating pattern 311 may be an opening or an insulating material filled in the opening, which is sufficient to ensure that the position of the insulating pattern 311 is not conductive. Since the conductive mesh 31 is hexagonal in shape, setting the shape of the insulating pattern 311 to be hexagonal or circular can improve the uniformity of the width of the conductive mesh lines in the same conductive mesh 31. Preferably, the shape of the insulating pattern 311 is set to be hexagonal, so that the widths of the conductive grid lines are the same in the same conductive grid 31. When the filling factor of the insulating patterns 311 is the same in all the conductive grids 31, the first electrode 30 is formed as a mesh electrode composed of conductive grid lines having the same thickness.
Fig. 6 is a schematic structural view of another first electrode provided by the embodiment of the present invention, fig. 7 is a schematic structural view of another first electrode provided by the embodiment of the present invention, fig. 8 is a schematic structural view of another first electrode provided by the embodiment of the present invention, and referring to fig. 6 to 8, on the basis of the above embodiment, as an alternative implementation manner of the present invention, the filling factor of the insulating pattern 311 increases stepwise, linearly, or non-linearly along the direction Y in which the center of the first electrode points to the edge.
Specifically, along the radius direction of the circular first electrode, the filling coefficient of the insulating pattern 311 gradually increases from the center of the circle to the outside, so that the carrier distribution with the maximum density generated in the middle area of the active region can be satisfied, the carrier density distribution is close to Gaussian distribution, and the fundamental mode gain can be higher in this way. The gain of the higher order mode is lower due to weaker carrier distribution at the edges. Thereby realizing the effect of enhancing the fundamental mode lasing and inhibiting the higher order mode. Since the excitation of the higher order mode also reduces the OPSR, the fundamental mode excitation is enhanced, and the suppression of the higher order mode can also increase the Orthogonal Polarization Suppression Ratio (OPSR).
Referring to fig. 6 and 7, along a direction Y in which the center of the first electrode 30 points to the edge, a direction in which the filling factor of the insulating pattern gradually increases may be stepwise increased. Referring to fig. 6, it is exemplarily drawn that the first electrode includes a first region 301 located at a central region and a second region 302 disposed around the first region 301. The filling factor of the insulating pattern in the first region 301 is smaller than that of the insulating pattern in the second region 302. Referring to fig. 7, it is exemplarily shown that the first electrode includes a first region 301 located at a central region, and a second region 302 and a third region 303 sequentially disposed around the first region 301. The filling factor of the insulating patterns in the first region 301 is the same, the filling factor of the insulating patterns in the second region 302 is the same, and the filling factor of the insulating patterns in the third region 303 is the same. And, the filling factor of the insulating pattern in the first region 301 is smaller than that of the insulating pattern in the second region 302, and the filling factor of the insulating pattern in the second region 301 is smaller than that of the insulating pattern in the third region 302.
Referring to fig. 8, along a direction Y in which the center of the first electrode is directed toward the edge, a direction in which the fill factor of the insulating pattern gradually increases may be linearly increased or non-linearly increased.
As an embodiment of the present invention, referring to fig. 6 to 8, optionally, the first electrode includes a first fully conductive region Q1, the first fully conductive region Q1 being located at a central region of the first electrode; in the first fully conductive region Q1, the filling factor of the insulating pattern inside the conductive mesh is equal to zero. It is understood that the first fully conductive region is located in the central region of the first electrode, so that the enhancement of the fundamental mode lasing can be further realized, and the effect of inhibiting the higher-order mode can be achieved.
Fig. 9 is a schematic structural view of another first electrode according to an embodiment of the present invention, and referring to fig. 9, as an alternative embodiment of the present invention, the first electrode is in an axisymmetric structure, and a direction of a symmetry axis L1 of the first electrode 30 is parallel to a fixed crystal direction; between a first boundary a and a second boundary B, which are at the same distance from the symmetry axis L1 and parallel to the symmetry axis L1, the filling factor of the insulating pattern inside the conductive mesh 31 is smaller than a first preset value; the filling factor of the conductive mesh internal insulation pattern on the side of the first boundary A far from the second boundary B and the filling factor of the conductive mesh internal insulation pattern on the side of the second boundary B far from the first boundary A are larger than a first preset value.
Specifically, the symmetry axis L1 of the first electrode is aligned with a specific crystal orientation, the filling coefficient is reduced in the specific crystal orientation direction, and non-uniform current injection in different crystal orientations is realized, so that polarization control is realized. The polarization control is mainly implemented to increase the orthogonal polarization suppression ratio, i.e. increase the output of one polarization state and suppress the other polarization state. Wherein the direction with a lower fill factor corresponds to a stronger polarized light. Referring to fig. 9, an exemplary illustration shows that the symmetry axis L1 is parallel to the crystal direction 1, the amplitude of polarized light having the polarization direction of the crystal direction 1 is stronger. Since the lasing of the higher order mode also reduces the Orthogonal Polarization Suppression Ratio (OPSR), a surface emitting laser such as a VCSEL is required to achieve a high Orthogonal Polarization Suppression Ratio (OPSR) while also meaning that the fundamental mode lasing is ensured. In order to prevent the excitation of higher order modes from decreasing the Orthogonal Polarization Suppression Ratio (OPSR), the embodiment of the invention sets the middle region to the lowest filling coefficient or the fully conductive region (Q1) while decreasing the filling coefficient in the specific crystal direction, so as to improve the fundamental mode gain and reduce the influence of the excitation of higher order modes on the Orthogonal Polarization Suppression Ratio (OPSR).
On this basis, fig. 10 is a schematic structural diagram of another first electrode according to an embodiment of the present invention, and referring to fig. 10, optionally, between the first boundary a and the second boundary B, along the direction of the center pointing edge of the first electrode 30, the filling factor of the insulating pattern 311 increases stepwise, linearly, or non-linearly. The gain of the fundamental mode can be made higher and the gain of the higher order mode is lower because the carrier distribution at the edge is weaker. Thereby further improving the orthogonal polarization suppression ratio.
Fig. 11 is a schematic structural view of another first electrode provided by an embodiment of the present invention, and fig. 12 is a schematic structural view of another first electrode provided by an embodiment of the present invention, referring to fig. 11 and fig. 12, as an alternative embodiment of the present invention, the first electrode includes a plurality of second fully conductive regions Q2; in the second fully conductive region Q2, the filling coefficient of the insulating pattern inside the conductive mesh is equal to zero; the first electrode may include one or more axes of symmetry; the second fully conductive areas Q2 are positioned at the edges of the different sides of the first electrode and are correspondingly arranged on a symmetry axis; the second fully conductive region is configured at different positions for forming a predetermined higher order mode of lasing.
Referring to fig. 11, an example is shown where the first electrode includes two second fully conductive regions Q2, one at each of opposite ends of the same axis of symmetry L1. Referring to fig. 12, an example is shown where the first electrode 30 includes three second fully conductive regions Q2; the first electrode comprises three symmetry axes, namely symmetry axis L1, symmetry axis L2 and symmetry axis L3. The three second fully conductive regions Q2 are disposed on different symmetry axes, respectively. By providing fully conductive regions on different symmetry axes, lasing of a particular higher order mode can be achieved.
Optionally, referring to fig. 1-3, the epitaxial layer further includes at least one oxide layer 24, and the oxide layer 24 includes a second opening; the oxide layer is used for limiting the flow direction of carriers.
Specifically, the oxide layer 24 may be formed by oxidizing the sidewall of the semiconductor layer (for example, the material of aluminum gallium arsenide) where the oxide layer is located by wet oxidation of highly aluminum doped under a certain temperature condition. The oxide layer 24 has a second opening, which is a semiconductor layer that is not oxidized, and is used to define the light emitting region of the laser. Such a structure may restrict current to pass only through the middle conductive portion. The oxidized aluminum oxide has high impedance, the second opening is still made of aluminum-doped AlGaAs material, and when current enters, the current flows to the multi-junction active region through the second opening. The multi-junction active region includes at least two active layers 22 for converting electrical energy into optical energy to generate laser light. The laser also includes a passivation layer 50 deposited on the surface, and a window of passivation layer is etched over the first electrode 30 to create a P Pad electrode. A window of passivation layer is etched over the second electrode 40 to make an N Pad electrode.
Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.

Claims (10)

1. A surface-emitting laser, comprising:
a substrate;
an epitaxial layer located on one side of the substrate; the epitaxial layer is used for forming a light-emitting platform, and the light-emitting platform comprises at least one active layer;
a first electrode located on a side of the epitaxial layer away from the substrate;
a second electrode located on a side of the substrate away from the epitaxial layer; or, the light emitting platform is positioned on one side of the substrate close to the epitaxial layer and surrounds the light emitting platform;
wherein the first electrode is a grid electrode formed by a plurality of conductive grids; each conductive grid comprises an insulating pattern with a corresponding filling coefficient; the insulating pattern is used for adjusting carrier densities of different positions of the active layer; the filling factor of the insulating pattern is the area ratio of the insulating pattern to the conductive mesh.
2. The surface emitting laser of claim 1, wherein the shape of the conductive mesh comprises a hexagon; the patterns of the first electrode are formed by splicing hexagons with the same area;
the shape of the insulating pattern includes at least one of a hexagon and a circle.
3. The surface-emitting laser according to claim 1, wherein a light-emitting direction is a direction in which the active layer is directed toward the substrate;
the second electrode comprises a first opening, and the area of the first opening is larger than or equal to the area of the light emergent hole;
the vertical projection of the first electrode on the second electrode is positioned in the area of the first opening.
4. The surface emitting laser according to claim 1, wherein a filling factor of the insulating pattern increases stepwise, linearly or non-linearly along a direction in which a center of the first electrode is directed toward an edge.
5. The surface emitting laser of claim 1, wherein the first electrode comprises a first fully conductive region, the first fully conductive region being located in a central region of the first electrode; in the first fully conductive region, the filling factor of the insulating pattern inside the conductive mesh is equal to zero.
6. The surface emitting laser according to claim 1, wherein the first electrode has an axisymmetric structure, and a symmetry axis direction of the first electrode is parallel to a fixed crystal direction;
the filling coefficient of the insulating pattern inside the conductive grid is smaller than a first preset value between a first boundary and a second boundary which are at the same distance from the symmetry axis and are parallel to the symmetry axis; the filling coefficient of the conductive grid internal insulation pattern on the side of the first boundary away from the second boundary and the filling coefficient of the conductive grid internal insulation pattern on the side of the second boundary away from the first boundary are larger than the first preset value.
7. The surface emitting laser according to claim 6, wherein a filling factor of the insulating pattern increases stepwise, linearly or non-linearly between the first boundary and the second boundary along a direction in which a center of the first electrode points to an edge.
8. The surface emitting laser of claim 1, wherein the first electrode comprises a plurality of second fully conductive regions; in the second fully conductive region, the filling coefficient of the insulating pattern inside the conductive mesh is equal to zero;
the first electrode includes a plurality of symmetry axes; the second fully conductive areas are positioned at the edges of the different sides of the first electrode and are correspondingly arranged on one symmetry axis; and the configuration of different positions of the second completely conductive region is used for forming the lasing of a preset high-order mode.
9. The surface emitting laser of claim 1, wherein the epitaxial layer further comprises at least one oxide layer, the oxide layer comprising a second opening; the oxide layer is used for limiting the flow direction of carriers.
10. A surface emitting laser according to any one of claims 1 to 9, wherein,
the epitaxial layer further comprises an upper Bragg reflection layer and a lower Bragg reflection layer, and the lower Bragg reflection layer is positioned between the active layer and the substrate; the upper Bragg reflection layer is positioned on one side of the active layer away from the substrate; the surface-emitting laser is of a vertical cavity surface-emitting laser type;
or, the epitaxial layer further comprises a two-dimensional photonic crystal layer, and the two-dimensional photonic crystal layer is positioned on one side of the active layer; the surface emitting laser is of a photonic crystal surface emitting laser type;
or, the epitaxial layer further comprises a widirac vortex structure, and the widirac vortex structure is located on one side of the active layer; the type of the surface emitting laser is a topological cavity surface emitting laser.
CN202310032186.8A 2023-01-10 2023-01-10 Surface emitting laser Pending CN116316051A (en)

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