A long wavelength surface emitting laser and a method for manufacturing the same

Abstract

The invention discloses a long-wavelength surface-emitting laser and a method for manufacturing the same, comprising: an InP substrate layer, an InP buffer layer, an N-type contact layer, an N-DBR, an N-spacer layer, a multi-junction cascade active region, a P-spacer layer, a buried tunnel junction, an InP leveling layer, a mixed medium mirror, and a P-type contact layer, which are sequentially arranged from bottom to top; wherein the N-DBR is fixedly connected to the top of the InP buffer layer, and the N-type contact layer is arranged around the N-DBR; the multi-junction cascade active region is fixedly connected to the top of the N-DBR through the N-spacer layer; the top of the multi-junction cascade active region is a p-spacer layer, and the upper side of the p-spacer layer is a buried tunnel junction surrounded by an InP leveling layer; and the top of the InP leveling layer is a mixed medium mirror. The long-wavelength surface-emitting laser structure of the invention improves the monochromaticity and thermal stability of the laser output beam, improves the output power and conversion efficiency of the device, enhances the environmental adaptability of the device, and optimizes the performance of the laser.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor laser optoelectronic technology, and in particular relates to a long-wavelength surface emitting laser and a manufacturing method thereof. Background Art

[0002] As an important optoelectronic device, long-wavelength vertical-cavity surface-emitting laser (LW-VCSEL) has been applied in the fields of long-distance optical communication and gas sensing. In long-distance optical communication, the operating wavelength of LW-VCSEL is mainly located at 1310nm and 1550nm. It has the characteristics of small transmission loss in optical fiber and good atmospheric penetration, providing products for high-bandwidth communication and long-distance transmission. In gas sensing, LW-VCSEL interacts with specific gases through spectral characteristics, and detects gases such as water, methane, carbon dioxide, carbon monoxide, hydrofluoric acid, and hydrochloric acid, achieving the advantages of high sensitivity, selective detection, and real-time monitoring, playing a vital role in environmental monitoring, industrial safety, medical agriculture, etc.

[0003] In terms of gas sensing, gases such as water, methane, carbon dioxide, carbon monoxide, hydrofluoric acid, and hydrochloric acid have spectral absorption peaks in the long wavelength range of 1280nm-2004nm. An InP-based long-wavelength surface-emitting laser structure is designed to achieve gas sensing, especially methane gas, with the help of the absorption peaks of these gases in this range. Although methane gas has an absorption spectrum near 1300nm and 1666nm, it has strong absorption at the 1654nm band and is not interfered by other gases. Therefore, the laser structure of the existing design has a lasing wavelength of about 1654nm. However, the laser structure in this band currently has problems such as low conversion efficiency, low output power, and low reliability. Therefore, it is urgent to improve the laser structure of the existing design. Summary of the invention

[0004] To solve the above problems, the present invention provides the following solution: a long-wavelength surface-emitting laser and a method for manufacturing the same. A long-wavelength surface-emitting laser comprises:

[0005] An InP substrate layer, an InP buffer layer, an N-type contact layer, an N-DBR, an N-spacer layer, a multi-junction cascade active region, a P-spacer layer, a buried tunnel junction, an InP filling layer, a mixed dielectric mirror, and a P-type contact layer are sequentially arranged from bottom to top;

[0006] Wherein, the N-DBR is fixedly connected to the top of the InP buffer layer, and the N-type contact layer is arranged around the N-DBR;

[0007] The multi-junction cascade active region is fixedly connected to the top of the N-DBR through an N spacer layer;

[0008] The top of the multi-junction cascade active region is a p-spacer layer, and the upper side of the p-spacer layer is a buried tunnel junction surrounded by an InP filling layer;

[0009] The top of the InP filling layer is a mixed dielectric mirror.

[0010] Preferably, the N-DBR is a stacked and fixed InGaAlAs / InAlAs having an optical thickness of one quarter of the target wavelength;

[0011] The N-DBR is connected to the multi-junction cascade active region through N spacer layers, and the thickness of the N-DBR is n times the optical thickness of half the target wavelength.

[0012] Preferably, the multi-junction cascade active region comprises an active region and a tunnel junction;

[0013] The tunnel junction is arranged on at least one side of the active region to connect with other active regions;

[0014] The tunnel junction uses N-type heavily doped and P-type heavily doped InGaAlAs, and the P-type doped layer is thicker than the N-type doped layer, wherein the In component is 0.4-0.6, the Ga component is 0.3-0.55, and the Al component is 0-0.2;

[0015] The active region is a multilayer structure of quantum wells and well barriers that are repeated alternately, specifically quantum wells and well barriers of InGaAsAl / InAsAl material, in which the In component is 0.1-0.7, the Ga component is 0.2-0.6, the Al component is 0.05-0.2, and the sum of the three components is 1.

[0016] Preferably, each active region has an optical thickness that is an integer multiple of half a wavelength. After the quantum well and well barrier structure allow the carriers to fully recombine, the carriers are reactivated through the tunnel junction and continue to flow into the next cascade active region to generate gain, so that the carriers continue to recombine in the next active region to generate photons, thereby adding more active regions to the periodic gain structure, improving the internal quantum efficiency of the device, and reducing the carrier density to obtain more gain.

[0017] Preferably, the buried tunnel junction is an N-type and P-type heavily doped InGaAs material, elliptical in shape, with a major axis size of 6-9 μm and a minor axis size of 4-8 μm, for limiting current and light field; and according to the target wavelength, the quantum well is placed at the crest of the standing wave, and the buried tunnel junction is placed at the node of the standing wave, for achieving large gain and small absorption loss.

[0018] Preferably, the hybrid dielectric mirror comprises AlF3 / ZnS and a composite film at the tail, and each layer of material has an optical thickness of one quarter of the target wavelength;

[0019] The composite film includes Si 3 N 4 / SiON composite film.

[0020] Preferably, the overall structure of the laser is an elliptical multi-table structure;

[0021] Wherein, the InP substrate layer and the InP buffer layer are first elliptical cylinders;

[0022] The N-DBR, N spacer layer, multi-junction cascade active region, and P spacer layer are a second elliptical cylinder;

[0023] The first elliptical cylinder and the second elliptical cylinder are coaxially arranged;

[0024] The table surface of the first elliptical cylinder is a first elliptical table surface;

[0025] The table surface of the second elliptical cylinder is a second elliptical table surface;

[0026] The table top of the mixed medium mirror is a third elliptical table top;

[0027] An N-type contact layer and a P-type contact layer are respectively disposed on the first elliptical table surface and the second elliptical table surface;

[0028] The buried tunnel junction is located on the P spacer layer in the second elliptical cylinder and is surrounded by an InP filling layer.

[0029] The present invention also provides a method for manufacturing a long-wavelength surface-emitting laser, comprising:

[0030] Based on the emitting laser structure, an elliptical cylindrical epitaxial structure is grown by molecular beam epitaxy or chemical vapor deposition;

[0031] According to the anisotropy of the material etching rate, the direction with faster etching rate is designed as the short axis part of the ellipse according to the etching rate in each direction, and the direction with slower etching rate is set as the long axis part of the ellipse to obtain a long wavelength surface emitting laser.

[0032] Preferably, the process of growing an elliptical cylindrical epitaxial structure by molecular beam epitaxy or chemical vapor deposition based on the emitting laser structure includes:

[0033] An InP buffer layer, an N-DBR, an N spacer layer, a multi-junction cascade active region, and a P spacer layer are sequentially epitaxially grown on an InP substrate layer, a buried tunnel junction and a filling layer are secondary epitaxially grown, and finally a mixed dielectric mirror is epitaxially grown.

[0034] Preferably, according to the anisotropy of the material etching rate, the direction with a faster etching rate is designed as the short axis part of the ellipse according to the etching rates in each direction, and the direction with a slower etching rate is set as the long axis part of the ellipse. The process includes:

[0035] The InP substrate layer and the InP buffer layer are etched by ICP-RIE to obtain a first elliptical cylindrical table;

[0036] The P spacer layer, the multi-junction cascade active region and the N spacer layer are etched by ICP-RIE to obtain the second elliptical cylindrical table;

[0037] An elliptical buried tunnel junction is dry-etched on the P spacer layer, and then filled with an InP filling layer, and a high-refractive index mixed medium mirror including a composite film with enhanced environmental adaptability is epitaxially grown on the InP filling layer; and then a heavily doped N-type contact layer and a P-type contact layer are electroplated on the first elliptical cylindrical table and the second elliptical cylindrical table, respectively, to obtain a long wavelength surface emitting laser.

[0038] Compared with the prior art, the present invention has the following advantages and technical effects:

[0039] The long-wavelength surface-emitting laser structure of the present invention adopts an InP-based substrate structure. The electron mobility and carrier lifetime of the InP-based VCSEL are relatively excellent, and it has higher power conversion efficiency and higher light output power in the long wavelength range, and can achieve higher output power and longer transmission distance; and it has relatively stable performance in a wide temperature range. In terms of process, the preparation technology of the InP-based VCSEL is relatively mature, and it has high preparability and reliability.

[0040] The long-wavelength surface-emitting laser structure of the present invention adopts a multi-junction cascade active region structure, and multiple active regions are connected together through tunnel junctions to form a multi-junction structure. On the one hand, the periodic stacking of active regions and tunnel junctions can improve the round-trip gain and gain volume, and on the other hand, the tunneling effect and carrier redistribution can be achieved through the tunnel junction, further improving the slope efficiency. In addition, the gain multiple of the multi-junction VCSEL is increased, and the loss per junction is lower. The gain multiple of the multi-junction VCSEL sharing the DBR is increased but the loss does not increase, and the series resistance is reduced, so that the voltage is lower and the efficiency is higher.

[0041] The long wavelength surface emitting laser structure of the present invention adopts an elliptical buried tunnel junction structure surrounded by an InP overgrowth layer to limit current and light field and enhance mode stability. InP material has excellent thermal conductivity and can efficiently conduct heat away from the active area, thereby improving the monochromaticity and thermal stability of the light emitted by the laser structure.

[0042] The long wavelength surface emitting laser structure of the present invention adopts a multi-junction structure containing multiple active regions, which lengthens the cavity length. On the one hand, it reduces the threshold current and improves the stability of the device; on the other hand, it reduces the possibility of output light mode hopping, facilitates single-mode operation and manufacturing, and optimizes the performance of the device.

[0043] The long-wavelength surface-emitting laser structure of the present invention adopts a mixed medium mirror containing a composite film, which enhances the environmental adaptability of the device and significantly increases the service life of the device.

[0044] In summary, the present invention uses an optimized InAlGaAs four-component strained quantum well active area design, including a multi-active area design, and a multi-group quantum well structure connected based on a tunnel junction to improve conversion efficiency and output power. The high-gain four-component quantum well design is used to increase output power. The current and light field of the device are limited by an elliptical tunnel junction to improve the mode stability of the device. High reflectivity is achieved by a dielectric reflector, and a high-quality resonant cavity is constructed together with a semiconductor reflector. The reliability and life of the device are improved by coating a composite film on the cutoff reflector. Finally, a long-wavelength surface-emitting laser structure is obtained, and the device structure is suitable for the light source requirements of methane gas sensing applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0046] Figure 1 is a cross-sectional schematic diagram of a long wavelength surface emitting laser according to an embodiment of the present invention;

[0047] Figure 2 It is a schematic diagram of the active region structure of a multi-junction cascade according to an embodiment of the present invention;

[0048] Figure 3 is a schematic top view of a long wavelength surface emitting laser according to an embodiment of the present invention;

[0049] Among them, 100, InP substrate layer; 200, InP buffer layer; 300, N-type contact layer; 400, N-DBR; 500, N spacer layer; 600, multi-junction cascade active area; 700, P spacer layer; 202, buried tunnel junction; 201, InP filling layer; 800, mixed dielectric mirror; 900, P-type contact layer; 102, first elliptical table; 103, second elliptical table; 104, third elliptical table; 401, InGaAlAs; 402, InAlAs; 601, quantum well; 602, well barrier; 603, first tunnel junction; 604, first active area; 605, second tunnel junction; 606, second active area; 607, third active area. DETAILED DESCRIPTION

[0050] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0051] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0052] Embodiment 1

[0053] like Figure 1 As shown, the present invention provides a long wavelength surface emitting laser, comprising:

[0054] An InP substrate layer 100, an InP buffer layer 200, an N-type contact layer 300, an N-DBR 400, an N-spacer layer 500, a multi-junction cascade active region 600, a P-spacer layer 700, a buried tunnel junction 202, an InP fill layer 201, a mixed dielectric mirror 800, and a P-type contact layer 900 are sequentially arranged from bottom to top;

[0055] Among them, the N-DBR 400 is fixedly connected to the top of the InP buffer layer 200, and the N-type contact layer 300 is arranged around the N-DBR 400; the multi-junction cascade active area 600 is fixedly connected to the top of the N-DBR 400, and is connected by an N spacer layer 500; at the top of the multi-junction cascade active area 600 is a P spacer layer 700, and above the P spacer layer 700 is a buried tunnel junction 202 surrounded by an InP filling layer 201, and on the top of the InP filling layer 201 is a mixed medium mirror 800.

[0056] Furthermore, the mixed medium mirror 800 is preferably AlF 3 / ZnS and the composite film at the tail, each layer of material has a quarter of the target wavelength optical thickness. 3 / ZnS has a very high emissivity, so a high reflector effect can be achieved with fewer pairs. The composite film has related functions such as water vapor resistance and heat resistance, which can be used to enhance the environmental adaptability and stability of the laser, such as Si 3 N 4 / SiON composite film. The buried tunnel junction 202 is elliptical and plays a role in limiting the current and light field. It is preferably N-type and P-type heavily doped InGaAs materials, elliptical in shape, with a major axis size of 6-9μm and a minor axis of 4-8μm. And according to the target wavelength, the quantum well is placed at the crest of the standing wave, and the buried tunnel junction 202 is placed at the node of the standing wave to achieve the purpose of large gain and small absorption loss. The present invention improves the monochromaticity and stability of the light emitted by the laser structure, optimizes the injection efficiency of the current, improves the output power and conversion efficiency of the device, and optimizes the performance of the laser.

[0057] like Figure 2 The multi-junction cascade active area structure shown contains multiple active areas and tunnel junctions, such as the first active area 604, the second active area 606, the third active area 607, the first tunnel junction 603, and the second tunnel junction 605. A tunnel junction is set on at least one side of the active area to connect with other active areas.

[0058] The tunnel junction preferably uses N-type heavily doped and P-type heavily doped InGaAlAs, the P-type doped layer is thicker than the N-type doped layer, wherein the In component is 0.4-0.6, the Ga component is 0.3-0.55, and the Al component is 0-0.2, and the more specific components are determined according to the target wavelength;

[0059] The active region is a multilayer structure of alternating quantum wells 601 and well barriers 602, preferably quantum wells and well barriers of InGaAsAl / InAsAl material, in which the In component is 0.1-0.7, the Ga component is 0.2-0.6, and the Al component is 0.05-0.2, and the sum of the three components is 1. The more specific components are determined according to the target wavelength to prevent the laser beam from being absorbed by the band gap.

[0060] Each active area has an optical thickness of an integer multiple of half a wavelength. After the quantum well and well-barrier structure allow the carriers to fully recombine, the carriers are reactivated through the tunnel junction and continue to flow into the next cascade active area to generate gain, so that the carriers continue to recombine in the next active area to generate photons. In this way, more active areas are added to the periodic gain structure, which improves the internal quantum efficiency of the device and reduces the carrier density, thereby obtaining more gain.

[0061] N-DBR 400 is a stacked and bonded InGaAlAs 401 and InAlAs 402 with a quarter target wavelength optical thickness. N-DBR 400 and multi-junction cascade active region 600 are connected by N spacer layer 500, whose thickness is n times the half target wavelength optical thickness. Preferably, the spacer layer is made of InAlAs material.

[0062] like Figure 3The top view of the device structure shown in FIG. 1 shows that the overall structure of the laser is an elliptical multi-table structure, the InP substrate layer 100 and the InP buffer layer 200 are a first elliptical cylinder, the N-DBR 400, the N spacer layer 500, the multi-junction cascade active region 600, and the P spacer layer 700 are a second elliptical cylinder, and the first elliptical cylinder and the second elliptical cylinder are coaxially arranged to facilitate heat dissipation of the laser;

[0063] The table of the first elliptical cylinder is the first elliptical table 102, the table of the second elliptical cylinder is the second elliptical table 103, and the mixed medium mirror table is the third elliptical table 104; the shaded parts on the first elliptical table 102 and the second elliptical table 103 are the heavily doped N-type contact layer 300 and the P-type contact layer 900, respectively. The dotted line part in the figure is the elliptical buried tunnel junction 202, which is located on the P spacer layer 700 in the second elliptical cylinder and is surrounded by the InP filling layer. The shaded parts are the N-type contact layer 300 and the P-type contact layer 900, respectively. The multi-table structure, multi-junction cascade active area 600, elliptical buried tunnel junction 202 and other structures improve the monochromaticity, mode stability and thermal stability of the output light from the three aspects of heat dissipation, output power and current limitation, and optimize the performance of the laser.

[0064] Embodiment 2

[0065] The present invention also discloses a method for manufacturing a long-wavelength surface-emitting laser, comprising:

[0066] According to the above-mentioned emitting laser structure, an elliptical cylindrical epitaxial structure is grown by molecular beam epitaxy or chemical vapor deposition method, that is, an InP buffer layer 200, an N-DBR 400, an N spacer layer 500, a multi-junction cascade active region 600, and a P spacer layer 700 are sequentially epitaxially grown on an InP substrate layer 100, a buried tunnel junction 202, an InP fill layer 201 are epitaxially grown for a second time, and finally a mixed dielectric mirror 800 is grown.

[0067] According to the anisotropy of the material etching rate, the direction with a faster etching rate is designed as the short axis part of the ellipse according to the values ​​of the etching rates in each direction, and the direction with a slower etching rate is set as the long axis part of the ellipse. The P spacer layer 700, the multi-junction cascade active area 600 and the N spacer layer 500 are etched by ICP-RIE to obtain the second elliptical table 103, the major axis of the second elliptical table 103 is 16-30μm, and the minor axis is 15-26μm. Similarly, the InP substrate layer and the InP buffer layer are etched by ICP-RIE to obtain the first elliptical table 102, the table size of the first elliptical table 102 is about 30μm larger than the table size of the second elliptical table 103, thereby obtaining the first elliptical table 102. An elliptical buried tunnel junction 202 is dry-etched on the P spacer layer 700, and then filled with an InP filling layer. A high-refractive-index mixed dielectric mirror 800 is grown on the InP filling layer 201, including a composite film for enhancing environmental adaptability. The preferred composite film thickness is 10nm or 20nm. The main body of the third elliptical table 104 is a mixed dielectric mirror table, with a major axis of 15-22μm and a minor axis of 10-16μm. The major axis size of the elliptical buried tunnel junction is 6-9μm, and the minor axis is 4-8μm, which is smaller than the size of the mixed dielectric mirror 800. Then, a heavily doped N-type contact layer 300 and a P-type contact layer 900 are electroplated on the first elliptical table and the second elliptical table, respectively. Figure 3 The circular shadow part in the standing wave field is formed by the contact layer, and the contact layer is located at the trough of the standing wave field to reduce the optical loss of the device. The first elliptical cylinder table, the second elliptical cylinder table and the third elliptical cylinder table in the laser structure of the present invention have good heat dissipation function, the multi-junction cascade active area improves the output power and conversion efficiency of the device, and the elliptical buried tunnel junction structure limits the current and the mode stability.

[0068] In summary, the laser structure of the present invention adopts InP-based substrate, multiple active regions, elliptical tunnel junction, mixed dielectric mirror and other structures to form a new type of surface emitting laser structure suitable for methane gas sensing applications. The long-wavelength surface emitting laser structure of the present invention improves the monochromaticity and thermal stability of the laser output beam, improves the output power and conversion efficiency of the device, enhances the environmental adaptability of the device, and optimizes the performance of the laser.

[0069] The present invention discloses a novel surface emitting laser structure and manufacturing method, which is a novel long-wavelength surface emitting laser composed of a multi-junction cascade active region, an elliptical buried tunnel junction, a mixed medium mirror containing a composite film, an elliptical table and other structures based on an InP-based substrate. The multi-junction cascade active region includes multiple active regions, but is not limited to 3, and may also be 4, 5, or more than or equal to 2. In the multiple active regions, each group of adjacent active regions is connected by a tunnel junction, and each active region is formed by multiple pairs of quantum wells and well barriers stacked alternately; the elliptical multi-table structure, the elliptical table is not limited to two, and may also be a multi-table structure of three, four, or more than one.

[0070] Furthermore, the laser structure is based on an InP-based long-wavelength surface-emitting laser structure, and the InP-based substrate structure improves the stability of the device and can support the stable output of a long-wavelength light beam.

[0071] The laser structure of the present invention includes a multi-active region structure, and a plurality of active regions are connected by tunnel junctions to form a multi-active region structure to improve the output power of the laser. In addition, the plurality of active regions connected by tunnel junctions form an expansion of the cavity, and such expansion lengthens the cavity length, can reduce the divergence angle of the emitted light, and improve the output beam quality.

[0072] The laser structure of the present invention adopts an elliptical buried tunnel junction structure. On the one hand, it realizes the function of current and light field limitation as a buried tunnel junction. On the other hand, the elliptical structure optimizes the polarization phenomenon of the device structure change, enhances the mode stability, and prevents the occurrence of mode hopping. The output mirror of the laser structure of the present invention uses a high refractive index mixed medium mirror structure, in which a composite film is added to improve the laser's resistance to water vapor, temperature, etc., protect the sensitivity of the sensor, and can significantly increase the service life of the device.

[0073] In general, the laser structure is suitable for the surface emitting laser structure of methane gas sensing application. The long wavelength surface emitting laser structure of the present invention improves the monochromaticity and thermal stability of the laser output beam, improves the output power and conversion efficiency of the device, enhances the environmental adaptability of the device, and optimizes the performance of the laser.

[0074] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A long wavelength surface emitting laser, characterized in that: include: An InP substrate layer, an InP buffer layer, an N-type contact layer, an N-DBR, an N-spacer layer, a multi-junction cascade active region, a P-spacer layer, a buried tunnel junction, an InP filling layer, a mixed dielectric mirror, and a P-type contact layer are sequentially arranged from bottom to top; Wherein, the N-DBR is fixedly connected to the top of the InP buffer layer, and the N-type contact layer is arranged around the N-DBR; The multi-junction cascade active region is fixedly connected to the top of the N-DBR through an N spacer layer; The top of the multi-junction cascade active region is a p-spacer layer, and the upper side of the p-spacer layer is a buried tunnel junction surrounded by an InP filling layer; The top of the InP filling layer is a mixed dielectric mirror; The N-DBR is a stacked and fixed InGaAlAs / InAlAs with an optical thickness of one quarter of the target wavelength; The N-DBR is connected to the multi-junction cascade active region through N spacer layers, and the thickness of the N-DBR is n times the optical thickness of half the target wavelength; The multi-junction cascade active region includes an active region and a tunnel junction; The tunnel junction is arranged on at least one side of the active region to connect with other active regions; The tunnel junction uses N-type heavily doped and P-type heavily doped InGaAlAs, and the P-type doped layer is thicker than the N-type doped layer, wherein the In component is 0.4-0.6, the Ga component is 0.3-0.55, and the Al component is 0-0.2; The active region is a multilayer structure of quantum wells and well barriers that are repeated alternately, specifically quantum wells and well barriers of InGaAsAl / InAsAl material, in which the In component of InGaAsAl is 0.1-0.7, the Ga component is 0.2-0.6, and the Al component is 0.05-0.2, and the sum of the three components is 1; The hybrid dielectric mirror includes AlF3 / ZnS and a composite film at the tail, and each layer of material has an optical thickness of one quarter of the target wavelength; The composite film includes a Si3N4 / SiON composite film.

2. The long wavelength surface emitting laser according to claim 1, characterized in that Each active area has an optical thickness of an integer multiple of half a wavelength. After the carriers are fully recombined through the quantum well and well barrier structure, the carriers are reactivated through the tunnel junction and continue to flow into the next cascade active area to generate gain, so that the carriers continue to recombine in the next active area to generate photons, thereby adding more active areas to the periodic gain structure, improving the internal quantum efficiency of the device, and reducing the density of carriers to obtain more gain.

3. The long wavelength surface emitting laser according to claim 1, characterized in that The buried tunnel junction is an N-type and P-type heavily doped InGaAs material, elliptical in shape, with a major axis size of 6-9μm and a minor axis size of 4-8μm, and is used to limit current and light field; and according to the target wavelength, the quantum well is placed at the crest of the standing wave, and the buried tunnel junction is placed at the node of the standing wave to achieve high gain and low absorption loss.

4. The long wavelength surface emitting laser according to claim 1, characterized in that The overall structure of the laser is an elliptical multi-table structure; Wherein, the InP substrate layer and the InP buffer layer are first elliptical cylinders; The N-DBR, N spacer layer, multi-junction cascade active region, and P spacer layer are a second elliptical cylinder; The first elliptical cylinder and the second elliptical cylinder are coaxially arranged; The table surface of the first elliptical cylinder is a first elliptical table surface; The table surface of the second elliptical cylinder is a second elliptical table surface; The table top of the mixed medium mirror is a third elliptical table top; An N-type contact layer and a P-type contact layer are respectively disposed on the first elliptical table surface and the second elliptical table surface; The buried tunnel junction is located on the P spacer layer in the second elliptical cylinder and is surrounded by an InP filling layer.

5. A method for manufacturing a long wavelength surface emitting laser according to claim 1, characterized in that: include: Based on the emitting laser structure, an elliptical cylindrical epitaxial structure is grown by molecular beam epitaxy or chemical vapor deposition; According to the anisotropy of the material etching rate, the direction with faster etching rate is designed as the short axis part of the ellipse according to the etching rate in each direction, and the direction with slower etching rate is set as the long axis part of the ellipse to obtain a long wavelength surface emitting laser.

6. The method for manufacturing a long wavelength surface emitting laser according to claim 5, characterized in that: Based on the emission laser structure, the process of growing the elliptical cylindrical epitaxial structure by molecular beam epitaxy or chemical vapor deposition method includes: An InP buffer layer, an N-DBR, an N spacer layer, a multi-junction cascade active region, and a P spacer layer are sequentially epitaxially grown on an InP substrate layer, a buried tunnel junction and a filling layer are secondary epitaxially grown, and finally a mixed dielectric mirror is epitaxially grown.

7. The method for manufacturing a long wavelength surface emitting laser according to claim 5, characterized in that: According to the anisotropy of the material etching rate, the direction with a faster etching rate is designed as the short axis part of the ellipse according to the etching rates in each direction, and the direction with a slower etching rate is set as the long axis part of the ellipse. The process includes: The InP substrate layer and the InP buffer layer are etched by ICP-RIE to obtain a first elliptical cylindrical table; The P spacer layer, the multi-junction cascade active region and the N spacer layer are etched by ICP-RIE to obtain the second elliptical cylindrical table; An elliptical buried tunnel junction is dry-etched on the P spacer layer, and then filled with an InP filling layer, and a high-refractive index mixed medium mirror including a composite film with enhanced environmental adaptability is epitaxially grown on the InP filling layer; and then a heavily doped N-type contact layer and a P-type contact layer are electroplated on the first elliptical cylindrical table and the second elliptical cylindrical table, respectively, to obtain a long wavelength surface emitting laser.

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