Horizontal cavity vertical emitting laser and preparation method thereof

Abstract

The invention relates to the technical field of lasers, and provides a preparation method of a horizontal-cavity vertical-emitting laser, which comprises the following steps: S1, manufacturing an epitaxial structure, S2, manufacturing a ridge waveguide on the epitaxial structure, S3, growing a mask layer to protect an area where the ridge waveguide is located, S4, etching an area outside the ridge waveguide on the epitaxial structure, manufacturing an inclined plane with an inclined angle of 45 degrees, and S5, manufacturing a horizontal-cavity vertical-emitting laser. And S5, manufacturing a reflecting surface on the inclined surface, enabling the light emitting end to emit horizontal laser to the reflecting surface, enabling the reflecting surface to reflect the horizontal laser into vertical laser, and enabling the vertical laser to be emitted out of the epitaxial structure. The invention also provides a horizontal-cavity vertical-emitting laser which is manufactured by adopting the method. The reflecting surface is manufactured on the epitaxial structure, the laser emitted by the light emitting end can be reflected into the vertical laser, and compared with traditional on-chip and off-chip schemes, the vertical light emitting device has the advantages of being low in cost, high in vertical light emitting efficiency and the like.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, in particular to a horizontal cavity vertical emission laser and a preparation method thereof. Background Art

[0002] For the infrared band laser light source of 3D structured light, the current mainstream technical solution is to use VCSEL (Vertical-Cavity Surface-Emitting Laser). The biggest problem with this solution is that the operating wavelength of VCSEL used for face recognition is 940nm, and the laser in the near-infrared spectrum region of 750nm to 1400nm is prone to cause safety problems for the human eye. The 940nm wavelength laser will focus on the retina of the human eye and will not trigger the protective blink reflex. This limits the intensity of the laser light source of 3D structured light, affecting the accuracy of face recognition and the ability to resist ambient light based on the structured light solution. However, the epitaxial growth of 1550nm wavelength VCSEL chips, which is safer for the human eye, is difficult and cannot be achieved at present, which greatly limits the face recognition ability of 3D structured light.

[0003] On the other hand, DFB (Distributed Feedback Laser) based on the indium phosphide material system has been widely used in the field of optical communications as a horizontal cavity resonant laser. Its operating wavelength covers 1200nm to 1700nm and can operate in a wavelength range that is safe for human eyes. Existing vertical emission solutions based on DFB lasers are divided into on-chip solutions and off-chip solutions. The off-chip solution mainly achieves vertical deflection of the horizontal beam by rotating the angle or introducing optical components in the package, and the structure is complex and costly; the on-chip solution mainly introduces a high-order grating to achieve vertical deflection of the horizontal beam. The vertical component of the high-order grating structure can achieve vertical deflection of the horizontal beam, but the coupling efficiency of the grating vertical component is low. Summary of the invention

[0004] The object of the present invention is to provide a horizontal cavity vertical emitting laser and a method for preparing the same, which can at least solve some of the defects in the prior art.

[0005] To achieve the above object, the embodiment of the present invention provides the following technical solution: a method for preparing a horizontal cavity vertical emitting laser, comprising the following steps:

[0006] S1, fabrication of epitaxial structure,

[0007] S2, fabricating ridge waveguide on the epitaxial structure,

[0008] S3, the growth mask layer protects the area where the ridge waveguide is located,

[0009] S4, etching the area outside the ridge waveguide on the epitaxial structure to form an inclined surface with an inclined angle of 45 degrees, and exposing the light emitting end of the epitaxial structure, the light emitting end is directly opposite to the inclined surface,

[0010] S5, making a reflecting surface on the inclined surface, the light emitting end emits a horizontal laser to the reflecting surface, and the reflecting surface reflects the horizontal laser into a vertical laser and emits it to the outside of the epitaxial structure.

[0011] Furthermore, an IBE (ion beam etching) etching method is used to etch the epitaxial structure to form an inclined surface.

[0012] Furthermore, during etching, a parallelepiped notch is first etched downward on the epitaxial structure, and the epitaxial structure forms mutually parallel inclined surfaces and a light emitting end at the notch, and then the light emitting end is etched into a vertical light emitting cavity surface.

[0013] Furthermore, the etching depth is between 10 and 50 μm.

[0014] Furthermore, the specific method for making the reflective surface is: growing a passivation layer and an anti-reflection film on the inclined surface, and then making a metal layer on the passivation layer and the anti-reflection film, and the metal layer is the reflective surface.

[0015] Furthermore, a P electrode is fabricated on the ridge waveguide, and a gap is provided between the reflection surface and the P electrode.

[0016] Furthermore, the epitaxial structure includes an active layer, an indium phosphide transition layer, a grating layer, a grating buried layer, an etching stop layer, a P-type indium phosphide waveguide layer and a contact layer which are sequentially grown on the substrate.

[0017] Furthermore, the P-type indium phosphide waveguide layer and the contact layer are etched to form a ridge waveguide.

[0018] Further, in step S4, etching is performed to the substrate layer.

[0019] The embodiment of the present invention provides another technical solution: a horizontal cavity vertical emitting laser, which is manufactured by the above method.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. By making a reflective surface on the epitaxial structure, the laser emitted by the light emitting end can be reflected into a vertical laser. Compared with traditional on-chip and off-chip solutions, it has the advantages of low cost and high vertical light output efficiency.

[0022] 2. Compared with the infrared light emitter of the VCSEL solution in the structured light of 3D face recognition, it has a long-wavelength working band of 1500nm to 1700nm. Under the premise of safety for human eyes, it can increase the output light power, enhance the anti-interference ability of face recognition, be insensitive to ambient light, and have higher recognition accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A front view of an epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0024] Figure 2 A three-dimensional diagram of an epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0025] Figure 3 A top view of a ridge waveguide is further shown on the epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0026] Figure 4 A stereoscopic diagram of a ridge waveguide is further shown on an epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0027] Figure 5 A parallelepiped main view is continued to be shown on the epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0028] Figure 6 A three-dimensional diagram of a parallelepiped is continued to be shown on the epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0029] Figure 7 A front view of a vertical light emitting end (light emitting cavity surface) is further shown on the epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0030] Figure 8 A three-dimensional diagram showing a vertical light emitting end (light emitting cavity surface) on an epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0031] Fig. 9 A front view of a passivation layer and an anti-reflection film is further shown on an epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0032] Fig.10 A stereoscopic view of a passivation layer and an anti-reflection film is further shown on an epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0033] Fig.11 A front view of a P electrode and a metal layer is further shown on an epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0034] Fig.12 A three-dimensional diagram of a P electrode and a metal layer is further shown on the epitaxial structure of a horizontal cavity vertical emitting laser provided by an embodiment of the present invention;

[0035] Fig.13 A schematic diagram of laser reflection of a horizontal cavity vertical emitting laser provided in an embodiment of the present invention;

[0036] In the figure markings: 1-substrate; 2-active layer; 3-indium phosphide transition layer; 4-grating layer; 5-grating buried layer; 6-etching stop layer; 7-P-type indium phosphide waveguide layer and contact layer; 8-passivation layer and anti-reflection film; 9-P electrode; 10-metal layer; 11-N electrode; 12-high reflective coating layer; 13-N substrate; 14-laser. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] See also Figures 1 to 12 The embodiment of the present invention provides a method for preparing a horizontal cavity vertical emitting laser, comprising the following steps: S1, making an epitaxial structure, S2, making a ridge waveguide on the epitaxial structure, S3, growing a mask layer to protect the area where the ridge waveguide is located, S4, etching the area other than the ridge waveguide on the epitaxial structure, making an inclined surface with a 45-degree inclination angle, and exposing the light emitting end of the epitaxial structure, the light emitting end is facing the inclined surface, S5, making a reflecting surface on the inclined surface, the light emitting end emits a horizontal laser to the reflecting surface, the reflecting surface reflects the horizontal laser into a vertical laser and emits it out of the epitaxial structure. Making a reflecting surface on the epitaxial structure can reflect the laser emitted by the light emitting end into a vertical laser, which has the advantages of low cost and high vertical light output efficiency compared to traditional on-chip and off-chip solutions. Fig.13 As shown, the horizontal laser can be reflected by the reflection surface and then emitted as a vertical laser. Preferably, the etching method uses an IBE etching method to etch the epitaxial structure to form an inclined surface.

[0039] As an optimization solution of the embodiment of the present invention, please refer to Figures 1 to 12 During etching, a parallelepiped notch is first etched downward on the epitaxial structure, and the epitaxial structure forms mutually parallel inclined surfaces and a light emitting end at the notch, and then the light emitting end is etched into a vertical light-emitting cavity surface. In this embodiment, the etching adopts the IBE etching method, and etching is performed by tilting and rotating the sample stage, so as to form a notch that looks like a parallelepiped, in which the light emitting end and the inclined surface are both inclined at 45 degrees. Preferably, the etching depth is between 10 and 50 μm, that is, the height of the parallelepiped is between 10 and 50 μm.

[0040] As an optimization solution of the embodiment of the present invention, please refer to Figures 1 to 12 The specific method of making the reflective surface is: growing a passivation layer and an anti-reflection film 8 on the inclined surface, and then making a metal layer 10 on the passivation layer and the anti-reflection film 8, and the metal layer 10 is the reflective surface. In this embodiment, the metal layer 10 can be a thin Au metal layer.

[0041] As an optimization solution of the embodiment of the present invention, please refer to Figures 1 to 12 , a P electrode 9 is made on the ridge waveguide, and there is a gap between the reflection surface and the P electrode 9. In this embodiment, the reflection surface and the P electrode 9 are not connected.

[0042] As an optimization solution of the embodiment of the present invention, please refer to Figures 1 to 12 The epitaxial structure includes an active layer 2, an indium phosphide transition layer, a grating layer 4, a grating buried layer 5, an etching stop layer 6, a P-type indium phosphide waveguide layer and a contact layer 7 grown sequentially on a substrate 1. Preferably, the P-type indium phosphide waveguide (P-type indium phosphide) layer and the contact layer are etched to form a ridge waveguide. In step S4, etching is performed to the substrate 1 layer.

[0043] The following is a specific implementation method:

[0044] (1) Using MOCVD (metal organic chemical vapor deposition) to sequentially grow an active layer 2, an indium phosphide transition layer 3, and a grating layer 4 on an indium phosphide substrate 1, using EBL technology and etching technology to make a grating, and using MOCVD to continue to bury and grow a grating buried layer 5, an etching stop layer 6, a P-type indium phosphide waveguide and a contact layer 7, as shown in FIG. Figure 1 , Figure 2 As shown;

[0045] (2) Using photolithography and etching techniques, a phosphoric acid-based etching solution is used to etch the P-type indium phosphide waveguide and the contact layer 7 into a ridge waveguide, such as Figure 3 , Figure 4 As shown;

[0046] (3) Then, a PECVD (plasma enhanced chemical vapor deposition) is used to grow a mask layer, and a photolithography and etching process is used to retain the mask layer in the ridge waveguide region. Then, an IBE etching technique is used to etch the area outside the mask layer in the ridge waveguide region to the indium phosphide substrate 1. The IBE etching technique can make the Ar+ ion beam generated by the IBE form a certain angle with the wafer surface by tilting and rotating the sample stage. In this embodiment, a 45° angle and an etching depth of 10 to 50 μm are optimal. Then, the mask layer is removed, as shown in FIG. Figure 5 , Figure 6 As shown;

[0047] (4) Use PECVD to grow the mask layer again, use photolithography and etching processes to retain the mask layer of the ridge waveguide area and the reflector area, and then use etching technology to etch the IBE etching slope close to the ridge waveguide to the indium phosphide substrate 1. The etching depth must be greater than the IBE etching depth of S3 to form a groove-shaped etching area, keep the light output cavity surface vertical, and then remove the mask layer, such as Figure 7 , Figure 8 As shown;

[0048] (5) Then, a passivation layer and an anti-reflection film 8 in the light-emitting direction are grown using PECVD, and the P-electrode contact is opened using photolithography and etching processes, such as Fig. 9 , Fig.10 As shown;

[0049] (6) Make a P electrode pad 9 on the ridge waveguide, and then make an Au metal thin layer 10 on the reflective slope as the reflective surface of the reflector to reflect the laser 14 emitted by the laser in the vertical direction. Note that the Au metal thin layer 10 and the P electrode pad 9 cannot be connected. Fig.11 , Fig.12 As shown;

[0050] (7) Then thinning, making N-type electrode 11, alloying, then stripping, using dielectric film coating equipment to make high-reflective coating layer 12, stripping to complete the production of laser, and finally performing chip packaging, sticking the laser on N-type substrate 13, as shown in FIG. Fig.13 Schematic diagram of the reflective surface effect.

[0051] The embodiment of the present invention provides a horizontal cavity vertical emitting laser, which is manufactured by the above method. Fig.12 The horizontal cavity vertical emitting laser includes an epitaxial structure, the epitaxial structure includes a ridge waveguide area, the top of the epitaxial structure is recessed downward to form a light reflection area, the light reflection area is located on one side of the ridge waveguide area, the ridge waveguide area has a ridge waveguide and a light emitting end, the light emitting area has a reflection surface that can reflect the laser emitted by the light emitting end into a vertical laser, and the light emitting end and the reflection surface are both located in the recess. In this embodiment, the epitaxial structure can be divided into a ridge waveguide area and a light reflection area, a ridge waveguide is arranged in the ridge waveguide area, and a P electrode 9 is arranged on the ridge waveguide. A light emitting end or a light exit cavity surface and a reflection surface are formed in the light reflection area. A notch is formed in the light emitting area by recessing downward, and the notch is obtained by the above-mentioned etching method. The structure of the horizontal cavity vertical emitting laser does not limit the preparation process, and other methods except etching can be used in the horizontal cavity vertical emitting laser, which is not limited in this embodiment.

[0052] As an optimization solution of the embodiment of the present invention, please refer to Fig.12, the light emitting end is arranged vertically, and the reflecting surface is arranged at an angle of 45 degrees. In this embodiment, the light emitting end or the light emitting cavity surface is arranged vertically, so that the active layer 2 emits horizontal laser light, and then the vertical laser light is obtained by reflecting the reflecting surface inclined at 45 degrees. Of course, this embodiment may not limit the direction of the laser light emitted by the light emitting end, and we may obtain vertical laser light by designing the inclination angle of the reflecting surface accordingly.

[0053] As an optimization solution of the embodiment of the present invention, please refer to Fig.12 The epitaxial structure includes an active layer 2, and the laser is emitted from the active layer 2. In this embodiment, the laser is emitted from the active layer 2, so the surface of the active layer 2 is the light-emitting cavity surface.

[0054] As an optimization solution of the embodiment of the present invention, please refer to Fig.12 The epitaxial structure further includes an indium phosphide transition layer 3, a grating layer 4, a grating buried layer 5, an etching stop layer 6, a P-type indium phosphide waveguide layer and a contact layer 7 which are sequentially stacked on the active layer 2. The active layer 2 is disposed on the substrate 1. Preferably, a ridge waveguide is formed on the P-type indium phosphide waveguide layer and the contact layer 7. A P electrode 9 is disposed on the ridge waveguide. A grating is disposed on the grating layer 4. The bottom of the depression sinks into the substrate 1, as shown in FIG. Fig.12 As shown, the depth of the depression can reach the substrate 1, and then a step structure can be formed at the depression through the above-mentioned etching process, and the step structure is located at the bottom of the reflective surface. The lowest step of the step structure is set at 90 degrees to the light emitting end, and the higher step cannot block the horizontal laser, which needs to be projected onto the reflective surface. Preferably, the wavelength of the laser emitted by the light emitting end is between 1500 and 1700 nm, which can increase the output light power under the premise of safety for human eyes, enhance the anti-interference ability of face recognition, be insensitive to ambient light, and have higher recognition accuracy.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a horizontal cavity vertical emitting laser, characterized in that: The steps include: S1, fabrication of epitaxial structure, S2, fabricating ridge waveguide on the epitaxial structure, S3, the growth mask layer protects the area where the ridge waveguide is located, S4, etching the area outside the ridge waveguide on the epitaxial structure to form an inclined surface with an inclined angle of 45 degrees, and exposing the light emitting end of the epitaxial structure, the light emitting end is directly opposite to the inclined surface, S5, making a reflecting surface on the inclined surface, the light emitting end emits a horizontal laser to the reflecting surface, and the reflecting surface reflects the horizontal laser into a vertical laser and emits it to the outside of the epitaxial structure.

2. The method for preparing a horizontal cavity vertical emitting laser according to claim 1, characterized in that: The epitaxial structure is etched by IBE (ion beam etching) to form an inclined surface.

3. The method for preparing a horizontal cavity vertical emitting laser according to claim 1, characterized in that: During etching, a parallelepiped notch is first etched downward on the epitaxial structure, and the epitaxial structure forms mutually parallel inclined surfaces and a light emitting end at the notch. Then, the light emitting end is etched into a vertical light emitting cavity surface.

4. The method for preparing a horizontal cavity vertical emitting laser according to claim 3, characterized in that: The etching depth is between 10 and 50 μm.

5. The method for preparing a horizontal cavity vertical emitting laser according to claim 1, characterized in that: The specific method for making the reflective surface is: growing a passivation layer and an anti-reflection film on the inclined surface, and then making a metal layer on the passivation layer and the anti-reflection film, and the metal layer is the reflective surface.

6. The method for preparing a horizontal cavity vertical emitting laser according to claim 1, characterized in that: A P electrode is fabricated on the ridge waveguide, with a gap between the reflection surface and the P electrode.

7. The method for preparing a horizontal cavity vertical emitting laser according to claim 1, characterized in that: The epitaxial structure comprises an active layer, an indium phosphide transition layer, a grating layer, a grating buried layer, an etching stop layer, a P-type indium phosphide waveguide layer and a contact layer which are sequentially grown on a substrate.

8. The method for preparing a horizontal cavity vertical emitting laser according to claim 7, characterized in that: The P-type indium phosphide waveguide layer and the contact layer are etched to form a ridge waveguide.

9. The method for preparing a horizontal cavity vertical emitting laser according to claim 7, characterized in that: In step S4, etching is performed to the substrate layer.

10. A horizontal cavity vertical emitting laser, characterized in that: The method is prepared by any one of claims 1 to 9.

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