Vcsel laser with mode regulation function and preparation method thereof

Abstract

The application provides a VCSEL laser with a mode control function and a preparation method thereof. The VCSEL laser comprises an output light outlet of a high-order mode light beam and a basic mode light beam, and a mode control structure for turning the high-order mode light beam is prepared on the surface of the output light outlet, so that the high-order mode light beam is separated from the basic mode light beam. Compared with the prior art, the mode control structure is integrated on the surface of the VCSEL, only the high-order mode light beam at the edge of the output hole is filtered, the stable output of the basic mode light beam in the central region is not affected, the output loss of the basic mode light beam is not reduced, and the preparation process is simple.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of VCSEL laser, in particular to a VCSEL laser with mode regulation function and a preparation method thereof. BACKGROUND

[0002] With the development of information society, new quantum sensing, optical biomedicine and even optical quantum control fields have put forward new demands for the mode characteristics of VCSEL output laser. Since the traditional VCSEL structure is a cylindrical symmetric waveguide, the single-mode output requires the light emitting hole size to be controlled within 3 μm, which is extremely difficult in process, and limits the output power of the VCSEL laser. How to realize the stable output of the base transverse mode of the high-power vertical cavity surface emitting laser under a large light emitting hole has become a research hotspot at home and abroad.

[0003] In order to solve the above problems of the VCSEL laser, a complex mode filtering structure is generally integrated in the central area of the VCSEL surface, such as a photonic crystal structure, to filter the base mode and high-order mode synchronously. The photonic localization characteristics of the photonic crystal are used to etch the photonic crystal structure on the surface of the distributed Bragg reflector (DBR), utilize the refractive index difference between the photonic crystal pattern and the defect area, confine the light in the defect area of the photonic crystal, change the transverse mode distribution in the cavity, and realize the stable output of single mode under a large light emitting hole. However, such photonic crystal structure has the disadvantages of large power consumption and complex preparation process. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art, and provide a VCSEL laser with mode regulation function and a preparation method thereof. The high-order mode is filtered by integrating a mode regulation structure on the surface of the laser, and the stable output of single mode under a large light emitting hole is realized.

[0005] In order to achieve the above purpose, the following specific technical solutions are adopted in the present application:

[0006] The VCSEL laser with mode regulation function provided by the present application comprises a light emitting hole for outputting high-order mode light beams and base mode light beams, and a mode regulation structure for turning the high-order mode light beams is prepared on the surface of the light emitting hole, so that the high-order mode light beams and the base mode light beams are separated.

[0007] Preferably, the mode regulation structure is a microlens or a grating.

[0008] Preferably, the microlens is a cylindrical structure with a light emitting hole in the inside, and the diameter of the light emitting hole gradually increases along the light emitting direction.

[0009] Preferably, the cylindrical structure is a prismatic structure or a cylindrical structure.

[0010] Preferably, the material of the microlens is photoresist, and a high-reflection film is deposited on the surface of the light-emitting hole.

[0011] Preferably, the grating is a circular grating or a square grating, and a light-emitting hole is formed in the center of the circular grating or the square grating.

[0012] Preferably, the VCSEL laser with the mode control function further comprises, from bottom to top, an N-face electrode, a substrate, an N-type DBR layer, an active layer, an oxidation layer, a P-type DBR layer, and a P-face electrode, and the P-face electrode is located at the periphery of the light-emitting port.

[0013] Preferably, an unoxidized oxidation hole is formed in the oxidation layer corresponding to the position of the light-emitting port, and the aperture of the light-emitting hole near one end of the light-emitting port is smaller than the aperture of the oxidation hole.

[0014] Preferably, epoxy resin is used to reinforce between the microlens or the grating and the P-type DBR layer.

[0015] The application provides a preparation method of the VCSEL laser with the mode control function, comprising the following steps:

[0016] S1, preparing a VCSEL laser body; wherein the light-emitting port of the VCSEL laser body emits a high-order mode light beam and a fundamental mode light beam;

[0017] S2, preparing a mode control structure on the surface of the light-emitting port; wherein the mode control structure is used to bend the high-order mode light beam, so that the high-order mode light beam is separated from the fundamental mode light beam.

[0018] Preferably, the mode control structure is a microlens, and the preparation method of the microlens comprises the following steps:

[0019] S201, spin-coating photoresist on the surface of the light-emitting port;

[0020] S202, performing ultraviolet exposure through a photoetching process to transfer a photoetching plate pattern to the light-emitting port, to form a cylindrical photoresist;

[0021] S203, heating the cylindrical photoresist to a molten state, so that the cylindrical photoresist melts into a spherical dome shape under the action of surface tension;

[0022] S204, depositing a layer of high-reflection film on the surface of the spherical dome-shaped photoresist;

[0023] S205, preparing a masking layer on the high-reflection film, and etching the spherical dome-shaped photoresist into a ring structure by using a photoetching process.

[0024] Preferably, the mode control structure is a grating, and the preparation method of the grating comprises the following steps:

[0025] S210, depositing a silicon material on the surface of the light outlet by a physical vapor deposition process;

[0026] S220, spin-coating a photoresist on the surface of the silicon material, and performing an electron beam exposure process on the photoresist by using a mask plate to prepare a grating mask;

[0027] S230, performing etching on the surface of the silicon material by using the grating mask to form a grating by a dry etching process.

[0028] Preferably, in the process of preparing the VCSEL laser body, the following steps are specifically included:

[0029] S101, alternately growing N-doped materials with different components on a substrate to form an N-type DBR layer by a metal organic chemical vapor deposition process;

[0030] S102, growing an active layer on the N-type DBR layer;

[0031] S103, growing an oxidation layer on the active layer;

[0032] S104, alternately growing P-doped materials with different components on the oxidation layer to form a P-type DBR layer;

[0033] S105, etching from the P-type DBR layer to the active layer to form a mesa, and performing side oxidation on the oxidation layer to form an oxidation hole in the oxidation layer;

[0034] S106, evaporating metal on the surface of the P-type DBR layer to form a P-face electrode, the surface being located at the periphery of the light outlet;

[0035] S107, after thinning and polishing the substrate, evaporating metal to form an N-face electrode.

[0036] Compared with the prior art, the application integrates a mode regulation structure on the surface of the VCSEL, only filters out the high-order mode light beams at the edge of the light outlet, does not affect the stable output of the base film light beams in the central region, does not reduce the output loss of the base mode light beams, and has the advantages of simple preparation process. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a perspective view of a VCSEL laser with a mode regulation function provided according to Embodiment 1 of the application;

[0038] Figure 2 is a front view of Figure 1 ;

[0039] Figure 3 is a top view of Figure 1 ;

[0040] Figure 4is a flow chart of a micro-lens manufacturing method according to the embodiment 1 of the present application;

[0041] Figure 5 is a perspective view of a VCSEL laser with mode control function according to the embodiment 2 of the present application;

[0042] Figure 6 is Figure 5 a front view;

[0043] Figure 7 is Figure 5 a top view.

[0044] The reference signs in the drawings include: substrate 1, N-type DBR layer 2, active layer 3, oxidation layer 4, P-type DBR layer 5, P-face electrode 6, N-face electrode 7, micro-lens 8, high-order mode light beam 9, single mode light beam 10, substrate 1', N-type DBR layer 2', active layer 3', oxidation layer 4', P-type DBR layer 5', P-face electrode 6', N-face electrode 7', grating 8', high-order mode light beam 9', single mode light beam 10'. DETAILED DESCRIPTION

[0045] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0046] In order to make the objectives, technical solutions, and advantages of the present application clearer, further detailed descriptions will be given below in combination with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not constitute a limitation on the present application.

[0047] The present application provides a VCSEL laser with mode control function, a mode control structure is prepared on the surface of the light outlet, the high-order mode light beam is turned through the mode control structure, so that the direction of the high-order mode light beam deviates from the direction of the fundamental mode light beam.

[0048] Since the fundamental mode light beam of the VCSEL laser is mainly distributed in the central region of the light outlet, and the high-order mode is mainly distributed in the peripheral region of the light outlet, the mode control structure is provided with a light outlet hole, which does not shield the central region of the light outlet, but shields the edge region of the light outlet, so that the mode control structure only filters the high-order mode light beam distributed in the edge position of the light outlet, and does not affect the stable output of the fundamental mode light beam.

[0049] The material system of the VCSEL laser includes but is not limited to GaAs, GaN, InP, etc.

[0050] The mode control structure is not limited in shape, including but not limited to circular or polygonal.

[0051] The mode control structure can be a circular microlens or a grating. The structure of the VCSEL laser will be described below using microlenses and gratings as specific examples.

[0052] Example 1

[0053] like Figures 1-3 As shown, the VCSEL laser includes a substrate 1, an N-type DBR layer 2 fabricated on the surface of the substrate 1, an active layer 3 fabricated on the surface of the N-type DBR layer 2, an oxide layer 4 fabricated on the surface of the active layer 3, an unoxidized oxide hole formed inside the oxide layer 4 corresponding to the position of the light exit port, the aperture of the oxide hole is usually smaller than the aperture of the light exit port, a P-type DBR layer 5 fabricated on the surface of the oxide layer 4, a P-surface electrode 6 fabricated on the surface of the P-type DBR layer 5 corresponding to the position of the light exit port, an N-surface electrode 7 fabricated on the bottom surface of the substrate 1, and a microlens 8 fabricated on the P-type DBR layer 5 corresponding to the position of the light exit port.

[0054] The microlens 8 is a cylindrical structure with an internal light-emitting hole. Of course, the microlens 8 can also be a prismatic structure. The diameter of the light-emitting hole gradually increases along the light-emitting direction, forming a funnel-shaped structure. The diameter of the light-emitting hole at the end near the light-emitting opening is smaller than the diameter of the oxide hole, so that the microlens 8 covers the edge of the light-emitting hole.

[0055] The microlens is made of photoresist, and a high-reflectivity film is deposited on the surface of the light-emitting aperture. The high-reflectivity film reflects the high-order mode beam 9 that reaches the microlens, causing the output direction of the high-order mode beam 9 to deviate from the output direction of the fundamental mode beam 10, and the fundamental mode beam 10 is stably output from the light-emitting aperture.

[0056] Epoxy resin is used to reinforce the space between the upper surface of the laser and the microlens 8.

[0057] The fabrication method of a VCSEL laser includes the following steps:

[0058] S1. N-type DBR layers with different compositions of N-doped AlGaAs are alternately grown on the substrate by metal-organic chemical vapor deposition process.

[0059] S2. An active layer is grown on the N-type DBR layer.

[0060] S3. Grow an AlAs oxide layer on the active layer.

[0061] S4. P-doped AlGaAs with different compositions are alternately grown on the oxide layer to form a P-type DBR layer.

[0062] S5. Etch from the P-type DBR layer to the active layer to form a mesa, and perform side oxidation on the oxide layer to form oxide holes within the oxide layer.

[0063] S6, a light outlet is prepared on the center of the surface of the P-type DBR layer by a photoetching process.

[0064] The size of the light outlet is generally larger than that of the oxidation hole.

[0065] S7, a P-face electrode is formed by evaporating metal on the surface of the P-type DBR layer at the periphery of the light outlet.

[0066] S8, after the substrate is thinned and polished, an N-face electrode is formed by evaporating metal.

[0067] S9, a photoresist is spin-coated on the surface of the light outlet.

[0068] S10, the photoresist is exposed to ultraviolet light by a photoetching process, and the photoetching plate pattern is transferred to the light outlet to form a cylindrical photoresist.

[0069] S11, the cylindrical photoresist is heated to a molten state, and the cylindrical photoresist is melted into a spherical dome shape under the action of surface tension.

[0070] S12, a high-reflection film is deposited on the surface of the spherical dome-shaped photoresist.

[0071] S13, a mask layer is prepared on the high-reflection film, and the spherical dome-shaped photoresist is etched into a ring structure by a photoetching process.

[0072] Steps S10-S13 are the specific process of making a microlens, as shown in Figure 4 .

[0073] Example 2

[0074] As shown in Figures 5-7 , the VCSEL laser includes a substrate 1`, an N-type DBR layer 2` is prepared on the surface of the substrate 1`, an active layer 3` is prepared on the surface of the N-type DBR layer 2`, an oxidation layer 4` is prepared on the surface of the active layer 3`, an unoxidized oxidation hole is formed in the oxidation layer 4` corresponding to the position of the light outlet, the aperture of the oxidation hole is generally smaller than that of the light outlet, a P-type DBR layer 5` is prepared on the surface of the oxidation layer 4`, a P-face electrode 6` is prepared on the surface of the P-type DBR layer 5` corresponding to the position of the light outlet, an N-face electrode 7` is prepared on the bottom surface of the substrate 1`, and a grating 8` is prepared on the P-type DBR layer 5` corresponding to the position of the light outlet.

[0075] The light grating 8' has an internal opening, which avoids affecting the fundamental mode light beam, and covers the edge position of the light outlet hole. The light grating 8' is a diffraction grating with transverse transmission characteristics, and is used for reflecting the high-order mode light beam 9' at the edge position of the light outlet hole, so that the high-order mode light beam 9' deviates from the direction of the fundamental mode light beam 10', thereby filtering out the high-order mode light beam 9' and realizing the output of the fundamental mode light beam 10' of the semiconductor laser. Since the fundamental mode light beam 10' is not affected, the stability of the fundamental mode light beam 9' can be ensured.

[0076] The preparation method of the VCSEL laser includes the following steps:

[0077] S1, alternately growing N-doped AlGaAs with different compositions on a substrate to form an N-type DBR layer.

[0078] S2, growing an active layer on the N-type DBR layer.

[0079] S3, growing an AlAs oxidation layer on the active layer.

[0080] S4, alternately growing P-doped AlGaAs with different compositions on the oxidation layer to form a P-type DBR layer.

[0081] S5, etching from the P-type DBR layer to the active layer to form a mesa, and side-oxidizing the oxidation layer to form an oxidation hole in the oxidation layer.

[0082] S6, preparing a light outlet hole at the center position of the surface of the P-type DBR layer through a photolithography process.

[0083] The size of the light outlet hole is generally larger than the size of the oxidation hole.

[0084] S7, evaporating metal on the surface of the P-type DBR layer at the periphery of the light outlet hole to form a P-face electrode.

[0085] S8, after thinning and polishing the substrate, evaporating metal to form an N-face electrode.

[0086] S9, depositing a silicon-based material on the surface of the light outlet hole through a physical vapor deposition process.

[0087] The silicon-based material is, for example, silicon nitride or silicon dioxide.

[0088] S10, spin-coating photoresist on the surface of the silicon-based material, and using a mask to perform an electron beam exposure process on the photoresist to prepare a grating mask.

[0089] First, the position of the annular grating is defined by a mask, and the annular grating is located above the light outlet hole. The size of the central hole of the annular grating is smaller than the size of the oxidation hole. The grating mask is prepared on the photoresist through an electron beam exposure process on the mask.

[0090] S11, using a grating mask to perform etching on the surface of the silicon material by a dry etching process to form a grating.

[0091] The grating has a transverse transmission characteristic. When the high-order mode light beams around the light outlet reach the grating, the high-order mode light beams are angularly deflected, so that the high-order mode light beams are deviated from the fundamental mode light beam. The central hole of the grating does not affect the stable output of the fundamental mode light beam, and the purpose of filtering the high-order mode light beam is achieved.

[0092] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, different embodiments or examples described in the present specification and the features of different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0093] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

[0094] The specific embodiments of the present application described above do not constitute a limitation on the scope of protection of the present application. Any various other corresponding changes and modifications made according to the technical concept of the present application shall be included in the scope of protection of the claims of the present application.

Claims

1. A VCSEL laser with mode modulation function, comprising an output port for outputting a higher-order mode beam and a fundamental mode beam, characterized in that, A mode control structure is fabricated on the surface of the light outlet to fold the higher-order mode beam, thereby separating the higher-order mode beam from the fundamental mode beam. An unoxidized oxide hole is formed within the oxide layer of the VCSEL laser at the position corresponding to the light exit port. The mode control structure is a microlens or a grating. The microlens is a columnar structure with an internal light exit hole, the diameter of which gradually increases along the light exit direction. The grating is a circular grating, which is a diffraction grating with lateral transmission characteristics. A light exit hole is formed at the center of the circular grating, and the diameter of the light exit hole near the light exit port is smaller than the diameter of the oxide hole, so that the mode control structure covers the edge of the light exit hole.

2. The VCSEL laser with mode modulation function as described in claim 1, characterized in that, The columnar structure is a prismatic structure or a cylindrical structure.

3. The VCSEL laser with mode modulation function as described in claim 1 or 2, characterized in that, The microlens is made of photoresist, and a high-reflectivity film is deposited on the surface of the light-emitting aperture.

4. The VCSEL laser with mode modulation function as described in claim 1, characterized in that, It also includes, from bottom to top, an N-side electrode, a substrate, an N-type DBR layer, an active layer, an oxide layer, a P-type DBR layer, and a P-side electrode, wherein the P-side electrode is located on the periphery of the light outlet.

5. The VCSEL laser with mode modulation function as described in claim 4, characterized in that, The microlens or grating is reinforced with epoxy resin to the P-type DBR layer.

6. A method for fabricating a VCSEL laser with mode modulation function as described in claim 1, characterized in that, Includes the following steps: S1. Fabricate a VCSEL laser body; wherein, the output port of the VCSEL laser body emits a higher-order mode beam and a fundamental mode beam; S2. A mode control structure is prepared on the surface of the light exit port; wherein, the mode control structure is used to deflect the higher-order mode beam, causing the higher-order mode beam to separate from the fundamental mode beam; an unoxidized oxide hole is formed in the oxide layer of the VCSEL laser corresponding to the position of the light exit port, the aperture of the light exit hole near the light exit port is smaller than the aperture of the oxide hole, so that the mode control structure covers the edge position of the light exit hole; the mode control structure is a microlens or a grating; the microlens is a columnar structure with an internal light exit hole, the diameter of the light exit hole gradually increases along the light exit direction; the grating is a circular grating or a square grating, the circular grating or the square grating is a diffraction grating with lateral transmission characteristics, and a light exit hole is formed in the center of the circular grating or the square grating.

7. The method for fabricating a VCSEL laser with mode modulation function as described in claim 6, characterized in that, The method for preparing the microlens includes the following steps: S201. Spin-coat photoresist onto the surface of the light outlet; S202. Ultraviolet exposure is performed through photolithography to transfer the photomask pattern onto the light outlet, forming a cylindrical photoresist. S203. The cylindrical photoresist is heated to a molten state, and under the action of surface tension, the cylindrical photoresist melts into a spherical dome shape; S204. A highly reflective film is deposited on the surface of a spherical dome-shaped photoresist. S205. A masking layer is prepared on the high reflectivity film, and the photoresist of the spherical dome is etched into a ring structure using a photolithography process.

8. The method for fabricating a VCSEL laser with mode modulation function as described in claim 6, characterized in that, The method for fabricating the grating includes the following steps: S210. A silicon-based material is deposited on the surface of the light outlet by a physical vapor deposition process. S220. Photoresist is spin-coated onto the surface of the silicon-based material, and an electron beam exposure process is performed on the photoresist using a mask to prepare a grating mask. S230. The grating is formed by etching the surface of the silicon material using the grating mask with a dry etching process.

9. The method for fabricating a VCSEL laser with mode modulation function as described in claim 6, characterized in that, The fabrication process of the VCSEL laser body includes the following steps: S101. An N-type DBR layer is formed by alternating growth of N-doped materials with different compositions on a substrate using a metal-organic chemical vapor deposition process. S102. An active layer is grown on the N-type DBR layer; S103. An oxide layer is grown on the active layer; S104. P-type DBR layers are formed by alternately growing P-doped materials with different compositions on the oxide layer. S105. Etch from the P-type DBR layer to the active layer to form a mesa, and perform side oxidation on the oxide layer to form oxide holes in the oxide layer; S106. A P-surface electrode is formed by depositing metal on the surface of the P-type DBR layer around the light outlet. S107. After thinning and polishing the substrate, metal is vapor-deposited to form an N-face electrode.

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