A narrow-linewidth vertical-cavity surface-emitting laser with asymmetric internal cavity modulation

Abstract

The invention discloses a narrow linewidth vertical cavity surface emitting laser regulated by an asymmetric inner cavity, and relates to the field of semiconductor lasers, in particular to a narrow linewidth vertical cavity surface emitting laser regulated by an asymmetric inner cavity and a preparation method thereof. The laser is provided with a first electrode, a P-type Bragg reflection unit, an oxidation restriction layer, an active layer, an expansion layer, an N-type Bragg reflection unit, a substrate and a second electrode in sequence from top to bottom. The P-type Bragg reflection unit comprises a P-type Bragg reflection layer with a preset P-DBR pair number stacked, and the N-type Bragg reflection unit comprises an N-type Bragg reflection layer with a preset N-DBR pair number stacked, thereby solving the problem of large linewidth of the existing vertical cavity surface emitting laser.

Description

Technical Field

[0001] The invention relates to the field of semiconductor lasers, in particular to a narrow-linewidth vertical cavity surface emitting laser controlled by an asymmetric inner cavity and a preparation method thereof. Background Art

[0002] Vertical cavity surface emitting lasers have unique advantages such as small size, low threshold current, high conversion efficiency, good longitudinal mode uniformity, and easy integration into large-area arrays. In recent years, they have aroused widespread research interest in the field of semiconductor lasers and are also rapidly expanding in the application-end market, including: 3D facial recognition, laser medical beauty, gas detection, smart home, lidar and other applications.

[0003] In the prior art, narrow linewidth vertical cavity surface emitting lasers usually require a linewidth less than 100MHz to reduce system noise. At present, the mainstream narrow linewidth vertical cavity surface emitting lasers on the market mainly achieve the purpose of narrowing the linewidth by increasing the length of the laser external cavity. On the one hand, this will increase the volume of the laser system, reduce the integration of the laser, and make the optical path system more complicated; on the other hand, the external cavity system causes the vertical cavity surface emitting laser to produce multi-longitudinal mode lasing, which often causes mode hopping as the current changes. It is necessary to accurately control the external cavity light feedback intensity to avoid the drift of the spectrum linewidth, which will increase the difficulty of operating the external cavity vertical cavity surface emitting laser and increase the cost. Due to the short effective cavity length (usually about 1 wavelength) of the existing vertical cavity surface emitting laser, it is difficult to achieve a linewidth of less than 20MHz.

[0004] In view of the above problems, the present invention designs a narrow-linewidth vertical cavity surface emitting laser with asymmetric inner cavity regulation and a preparation method thereof. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of large line width of existing vertical cavity surface emitting lasers. The present invention provides a narrow line width vertical cavity surface emitting laser with asymmetric inner cavity control and a preparation method thereof, and expands the effective cavity length of the vertical cavity surface emitting laser to about 2μm.

[0006] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0007] A narrow linewidth vertical cavity surface emitting laser regulated by an asymmetric inner cavity, wherein the laser is provided with a first electrode, a P-type Bragg reflection unit, an oxidation restriction layer, an active layer, an expansion layer, an N-type Bragg reflection unit, a substrate and a second electrode in sequence from top to bottom, wherein the P-type Bragg reflection unit comprises a stacked P-type Bragg reflection layer having a preset P-DBR pair number, and the N-type Bragg reflection unit comprises a stacked N-type Bragg reflection layer having a preset N-DBR pair number.

[0008] Optionally, the expansion layer is Al 0.9 Ga 0.1 As, the doping concentration of the extension layer is 2×10 18 cm -3 ; The thickness of the expansion layer ranges from 1 to 2 microns.

[0009] Optionally, the preset P-DBR logarithm is smaller than the preset N-DBR logarithm; the range of the preset P-DBR logarithm is 22-24, and the range of the preset N-DBR logarithm is 34-36.

[0010] Optionally, oxidation pores are provided on the oxidation restriction layer, and the diameter of the oxidation pores is 3-4 microns.

[0011] Optionally, the P-type Bragg reflection layer is Al 0.9 Ga 0.1 As and Al 0.12 Ga 0.88 As, the doping concentration of the P-type Bragg reflector is 3×10 18 cm -3 .

[0012] Optionally, the N-type Bragg reflection layer is Al 0.9 Ga 0.1 As and Al 0.12 Ga 0.88 As, the doping concentration of the N-type Bragg reflector is 2×10 18 cm -3 .

[0013] Optionally, a gradient layer is sandwiched between adjacent P-type Bragg reflection layers in the P-type Bragg reflection unit and / or between adjacent N-type Bragg reflection layers in the N-type Bragg reflection unit.

[0014] Optionally, the gradient layer is Al x Ga 1-x As, Al x Ga 1-x The As component variation range is: x=0.9-0.12; the thickness of the gradient layer is 10-20 nm.

[0015] Optionally, the first electrode and / or the second electrode is made of any one of gold, copper, graphite, silver or tin.

[0016] The present invention also provides a method for preparing an asymmetric inner cavity regulated narrow linewidth vertical cavity surface emitting laser, comprising the following steps:

[0017] S1, epitaxially growing an N-type Bragg reflection unit, an extension layer, an active layer, an oxidation restriction layer and a P-type Bragg reflection unit on a substrate in sequence;

[0018] S2. A first electrode is arranged on a side of the substrate away from the P-type Bragg reflection unit, and a second electrode is made on a side of the substrate away from the N-type Bragg reflection unit to obtain a vertical cavity surface emitting laser.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] 1. The invention relates to an asymmetric inner cavity regulated narrow line width vertical cavity surface emitting laser and a preparation method thereof, which increases the effective cavity length in the vertical cavity surface emitting laser by setting an expansion layer between the edge region and the N-type Bragg reflection unit, thereby reducing the line width of the vertical cavity surface emitting laser, simplifying the optical path system of the vertical cavity surface emitting laser, improving the integration of the laser and reducing the volume of the vertical cavity surface emitting laser.

[0021] 2. The present invention relates to an asymmetric cavity-regulated narrow-linewidth vertical cavity surface emitting laser and a preparation method thereof. By setting an oxidation restriction layer, the laser has good insulation properties, can effectively suppress electron leakage, and enable the vertical cavity surface emitting laser to achieve low-threshold single-mode laser output. And because the refractive index of the oxidation restriction layer is lower than that of the quantum well material in the active layer, the light field can be effectively confined in the oxidation restriction layer. In terms of light field design, the active layer (antinode) and the oxidation restriction layer (node) are precisely regulated at the light field standing wave position to reduce the absorption loss of the device. In addition, an oxidation hole is provided on the oxidation restriction layer, and an AlGaAs material containing a high Al component is introduced to form an electron blocking layer, which effectively limits the escape of carriers and suppresses leakage current.

[0022] 3. The present invention relates to an asymmetric cavity-controlled narrow-linewidth vertical cavity surface emitting laser and a preparation method thereof, wherein a P-type Bragg reflection unit is provided with N-type Bragg reflection layers with a preset N-DBR pair number, and an N-type Bragg reflection unit is provided with N-type Bragg reflection layers with a preset N-DBR pair number, adjacent P-type Bragg reflection layers are connected in series, and adjacent N-type Bragg reflection layers are connected in series, and series resistance is generated between adjacent P-type Bragg reflection layers and / or adjacent N-type Bragg reflection layers. By providing a gradient layer, the resistance between adjacent P-type Bragg reflection layers and / or adjacent N-type Bragg reflection layers is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of a narrow-linewidth vertical-cavity surface-emitting laser with asymmetric intracavity regulation.

[0024] Figure 2 Schematic diagram of the refractive index distribution and electric field distribution in the vertical cavity surface emitting laser.

[0025] Figure 3 Schematic diagram of the half-width at half maximum of the cold cavity reflection spectrum of the vertical cavity surface emitting laser.

[0026] Figure 4 Schematic diagram of the electrical performance test of the cold cavity reflection spectrum of the vertical cavity surface emitting laser.

[0027] Figure markings: 1-first electrode, 2-P-type Bragg reflection unit, 3-oxidation restriction layer, 4-active layer, 5-extension layer, 6-N-type Bragg reflection unit, 7-substrate, 8-second electrode, 10-vertical cavity surface emitting laser, 21-P-type Bragg reflection layer, 22-gradient layer, 31-oxidation hole, 61-N-type Bragg reflection layer.

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0029] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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. DETAILED DESCRIPTION

[0030] See also Figure 1 As shown, an embodiment of the present invention provides a narrow linewidth vertical cavity surface emitting laser 10 with asymmetric cavity regulation, wherein the laser is provided with a first electrode 1, a P-type Bragg reflection unit 2, an oxidation restriction layer 3, an active layer 4, an expansion layer 5, an N-type Bragg reflection unit 6, a substrate 7 and a second electrode 8 in sequence from top to bottom, wherein the P-type Bragg reflection unit 2 includes a P-type Bragg reflection layer 21 stacked with a preset P-DBR pair number, and the N-type Bragg reflection unit 6 includes an N-type Bragg reflection layer 61 stacked with a preset N-DBR pair number.

[0031] It should be understood that the narrow linewidth vertical cavity surface emitting laser 10 in the prior art usually achieves the purpose of narrowing the linewidth by increasing the length of the laser external cavity, which will increase the volume of the laser system, reduce the integration of the laser, make the optical path system more complicated, and also increase the cost. In the embodiment of the present invention, by setting the expansion layer 5 between the active layer 4 and the N-type Bragg reflection unit 6, it should be understood that since the effective mass of the hole is large and the mobility is much smaller than the electron mobility, most of the resistance comes from the P-type Bragg reflection unit 2 area. Increasing the number of layers of the P-type Bragg reflection layer 21 in the P-type Bragg reflection unit 2 too much will reduce the device efficiency and output power, and increase the device operating voltage, series resistance and heat loss. Therefore, when designing the asymmetric internal cavity regulated vertical cavity surface emitting laser 10, an extension layer 5 is added between the N-type Bragg reflection unit 2 and the active layer 4 to increase the effective cavity length, further reducing the line width of the vertical cavity surface emitting laser 10, simplifying the optical path system of the vertical cavity surface emitting laser 10, improving the integration of the laser and reducing the volume of the vertical cavity surface emitting laser 10. The problem of the large line width of the existing vertical cavity surface emitting laser 10 is solved. Compared with the conventional vertical cavity surface emitting laser 10, the effective cavity length is significantly increased, thereby reducing the line width.

[0032] Furthermore, the extended layer 5 is Al 0.9 Ga 0.1 As, the doping concentration of the extension layer 5 is 2×10 18 cm -3 ; The thickness of the expansion layer 5 ranges from 1 to 1.5 microns.

[0033] Understandably, according to the Schawlow-Townes laser linewidth principle:

[0034]

[0035]

[0036] In formula (1), Δν is the spectral linewidth of the laser, Δλ c is the reflection spectrum cold cavity line width, P0 is the output optical power, n sp is the population inversion factor, η0 is the light output coupling efficiency, and α is the linewidth enhancement factor. (2) Where T is the percentage of energy loss of light in a round trip in the resonant cavity, η g is the group velocity of the light wave, L c is the cavity length of the laser resonator.

[0037] According to the above formula, the laser spectral linewidth is mainly related to the laser output power P0, the linewidth enhancement factor α and the reflection spectrum cold cavity linewidth Δλ cSince the spectral line width is related to the cold cavity line width Δλ of the reflection spectrum c Compared with the output power P0 and the linewidth enhancement factor α, the reflection spectrum cold cavity linewidth Δλ c It has a greater impact on the laser spectral line width. At the same time, the reflection spectrum cold cavity line width Δλ c It is closely related to the quality factor of the laser resonant cavity. Therefore, increasing the quality factor of the resonant cavity length will make the frequency more stable and the spectral linewidth narrower.

[0038] In formula (1), Δv is the spectral linewidth of the laser, Δλ c is the reflection spectrum cold cavity line width, P0 is the output optical power, n sp is the population inversion factor, η0 is the light output coupling efficiency, and α is the linewidth enhancement factor. (2) Where T is the percentage of energy loss of light in a round trip in the resonant cavity, η g is the group velocity of the light wave, L c is the cavity length of the laser resonator.

[0039] According to the above formula, the laser spectral linewidth is mainly related to the laser output power P0, the linewidth enhancement factor α and the reflection spectrum cold cavity linewidth Δλ c Since the spectral line width is related to the cold cavity line width Δλ of the reflection spectrum c Compared with the output power P0 and the linewidth enhancement factor α, the reflection spectrum cold cavity linewidth Δλ c It has a greater impact on the laser spectral line width. At the same time, the reflection spectrum cold cavity line width Δλ c It is closely related to the quality factor of the laser resonant cavity. Therefore, increasing the quality factor of the resonant cavity length will make the frequency more stable and the spectral linewidth narrower.

[0040] It should be understood that the cold cavity line width is inversely proportional to the effective cavity length as shown in equation (2). Increasing the effective cavity length can reduce the cold cavity line width, thereby reducing the laser spectral line width. In this embodiment, the thickness of the expansion layer 5 is set to 1-1.5 microns.

[0041] Specifically, the thickness of the extension layer 5 can also range from 1 to 1.495 microns, 1.355 to 1.485 microns or 1.495 to 1.5 microns. Preferably, the thickness of the extension layer 5 is 1.495 microns. Therefore, by providing the extension layer 5, the effective cavity length of the vertical cavity surface emitting laser 10 is improved.

[0042] Further, the preset P-DBR logarithm is less than the preset N-DBR logarithm; the preset P-DBR logarithm ranges from 22 to 24, and the preset N-DBR logarithm ranges from 34 to 36. Preferably, the preset P-DBR logarithm is 24, and the preset P-DBR logarithm is 36. It should be understood that, since the effective mass of the hole is large and the mobility is much smaller than the electron mobility, most of the resistance comes from the P-type Bragg reflection unit 2 region. Excessive increase in the number of layers of the P-type Bragg reflection layer 21 in the P-type Bragg reflection unit 2 will reduce the device efficiency and output power, and increase the device operating voltage, series resistance and heat loss. Therefore, the preset P-DBR logarithm and / or the preset second preset number of layers cannot be too large, so that the refractive efficiency of the P-type Bragg reflection unit 2 and / or the P-type Bragg reflection unit 2 for the vertical cavity surface emitting laser 10 is improved, so it is selected to add a cavity length extension layer to the N-DBR to avoid the reduction of device efficiency and output power and the increase of device operating voltage, series resistance and heat loss.

[0043] Further, an oxidation hole 31 is provided on the oxidation restriction layer 3, and the diameter of the oxidation hole 31 is 3-4 microns. The diameter of the oxidation hole 31 can also be 3-3.6 microns, 3-3.4 microns or 3.6-4 microns. Specifically, the diameter of the oxidation hole 31 is 3 microns. By providing the oxidation restriction layer 3, it has good insulation, can effectively suppress electron leakage, and enable the vertical cavity surface emitting laser 10 to achieve low threshold single-mode laser output. And because the refractive index 21 of the oxidation restriction layer 3 is lower than the refractive index 21 of the quantum well material in the active layer 4, the binding of the light field can be effectively achieved in the oxidation restriction layer 3. In the light field design, the active layer 4 (antinode) and the oxidation restriction layer 3 (node) are respectively precisely controlled at the light field standing wave position to reduce the absorption loss of the device. In addition, an oxidation hole 31 is provided on the oxidation restriction layer 3, and an AlGaAs material containing a high Al component is introduced to form a hole blocking layer, which well limits the escape of carriers and suppresses the hole leakage current.

[0044] Furthermore, the P-type Bragg reflection layer 21 is Al 0.9 Ga 0.1 As and Al 0.12 Ga 0.88 As, the doping concentration of the P-type Bragg reflector 21 is 3×10 18 cm -3 Furthermore, the N-type Bragg reflection layer 61 is Al 0.9 Ga 0.1 As or Al 0.12 Ga 0.88 As, the doping concentration of the N-type Bragg reflector layer 61 is 2×10 18 cm -3. The active layer 4 can be used to generate a laser beam after being excited by current, and the material of the active layer 4 includes at least one of GaP, GaAs, AlGaAs, InGaAs, InGaAsP, AlGaInAs, GaN, AlSb, AlN, AlGaN, AlAs, InP, GaSb, InAs, InSb, HgTe, HgSe, ZnTe, CdS, ZnSe, ZnS, ZnO, Ga2O3, III-V and II-VI materials. A gradient layer 22 is sandwiched between adjacent P-type Bragg reflection layers 21 in the top P-type Bragg reflection unit 2 and / or adjacent N-type Bragg reflection layers 61 in the N-type Bragg reflection unit 6. By reasonably selecting the materials of the P-type Bragg reflection layer 21, the active layer 4 and the P-type Bragg reflection layer 21, and the doping concentration, the lasing efficiency and light extraction efficiency of the vertical cavity surface emitting laser 10 can be effectively improved.

[0045] Furthermore, the gradient layer 22 is Al x Ga 1-x As,Al x Ga 1-x The As component variation range is: x=0.9-0.12; the thickness of the gradient layer 22 is 10-20nm. The P-type Bragg reflection unit 2 is stacked with an N-type Bragg reflection layer 61 with a preset N-DBR logarithm, and the N-type Bragg reflection unit 6 is stacked with an N-type Bragg reflection layer 61 with a preset N-DBR logarithm. Adjacent P-type Bragg reflection layers 21 are connected in series, and adjacent N-type Bragg reflection layers 61 are connected in series. A series resistance is generated between adjacent P-type Bragg reflection layers 21 and / or adjacent N-type Bragg reflection layers 61. By setting the gradient layer 22, the resistance between adjacent P-type Bragg reflection layers 21 and / or adjacent N-type Bragg reflection layers 61 is reduced.

[0046] Furthermore, the material of the first electrode 1 and / or the second electrode 8 is any one of gold, copper, graphite, silver or tin.

[0047] The present invention also provides a method for preparing an asymmetric inner cavity regulated narrow linewidth vertical cavity surface emitting laser, comprising the following steps:

[0048] S1, epitaxially growing an N-type Bragg reflection unit, an extension layer, an active layer, an oxidation restriction layer and a P-type Bragg reflection unit on a substrate in sequence;

[0049] S2. A first electrode is arranged on a side of the substrate away from the P-type Bragg reflection unit, and a second electrode is made on a side of the substrate away from the N-type Bragg reflection unit to obtain a vertical cavity surface emitting laser.

[0050] The preparation method of the present invention can use metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) to perform epitaxy on each layer.

[0051] Example 1

[0052] A narrow linewidth vertical cavity surface emitting laser 10 with asymmetric cavity regulation, wherein the laser is provided with a first electrode 1, a P-type Bragg reflection unit 2, an oxidation restriction layer 3, an active layer 4, an extension layer 5, an N-type Bragg reflection unit 6, a substrate 7 and a second electrode 8 in order from top to bottom, wherein the P-type Bragg reflection unit 2 includes a P-type Bragg reflection layer 21 stacked with a preset P-DBR pair number, and the N-type Bragg reflection unit 6 includes an N-type Bragg reflection layer 61 stacked with a preset N-DBR pair number; the thickness of the extension layer 5 is greater than the thickness of the P-type Bragg reflection layer 21.

[0053] In this embodiment, the present invention proposes a design method for an 893.3nm narrow linewidth straight-cavity surface-emitting laser with asymmetric cavity regulation, which increases the thickness of the first 1.495 microns of the adjacent active layer 4 domain (n-type Al 0.9 Ga 0.1 As), and an oxidation hole 31 with a diameter of 3 μm is provided on the oxidation restriction layer 3,

[0054] The vertical cavity surface emitting laser 10 provided in this embodiment can:

[0055] 1. Increase the effective cavity length of the straight-cavity surface-emitting laser, the cold cavity linewidth is 0.0974nm, and under the working condition of 10mW power, the spectral linewidth can reach about 1.965MHz.

[0056] 2. An oxide hole 31 with a diameter of 3 μm is used to confine the current in the center of the device, so that the straight-cavity surface-emitting laser is mainly emitted in the fundamental transverse mode.

[0057] In order to verify the refractive index 21 distribution and electric field distribution in the narrow linewidth vertical cavity surface emitting laser 10 involved in the present invention, the following test example is carried out.

[0058] 1.1 Experimental design

[0059] Two treatment groups were set up in the experiment. The experimental group was the vertical cavity surface emitting laser 10 involved in Example 1, and the comparative group was the vertical cavity surface emitting laser without the expansion layer. Under the same experimental conditions, the optical and electrical performance tests were performed on them. After the inspection, the refractive index 21 distribution and electric field distribution of the vertical cavity surface emitting laser 10 were obtained respectively.

[0060] 1.2 Results Analysis

[0061] See also Figure 2, shows the simulated light field profile near the active layer 4 domain, the thick line 21 represents the real refractive index 21, the thin line 22 represents the resonant cavity standing wave, the thickness of the expansion layer 5 is increased, and the effective cavity length is significantly increased relative to the conventional vertical cavity surface emitting laser 10 design. For ordinary vertical cavity surface emitting laser 10 lasers, the resonant cavity cold cavity line width is generally greater than 0.2nm. For vertical cavity surface emitting laser 10 lasers with an output optical power of less than 1mW, the output spectrum line width can reach more than 1GHz.

[0062] For the narrow linewidth vertical cavity surface emitting laser 10 controlled by asymmetric inner cavity, due to the effect of increasing the effective cavity length, the cold cavity linewidth of the resonant cavity can reach less than 0.1nm. When the output optical power is 10mW, see Figure 3 As shown, (it should be noted that real is the actual simulation data, and fit is the Lorentz fitting data) when the FWHM half-maximum full width of the narrow-linewidth vertical cavity surface emitting laser 10 controlled by the asymmetric inner cavity is 0.0974nm, through theoretical calculation and analysis, the laser output spectral linewidth can reach about 1.965MHz, which is more than 2 orders of magnitude smaller than the linewidth of the traditional vertical cavity surface emitting laser 10.

[0063] See also Figure 4 It should be noted that Figure 4 In the figure, VI is the curve of voltage versus current, PI is the curve of power versus current, and PCE is the curve of photoelectric conversion efficiency versus current. It can be seen that in terms of electrical performance, the threshold current Ith of the vertical cavity surface emitting laser 10 can reach 0.373mA, the turn-on voltage V0 is 1.32V, the slope efficiency is 0.901W / A, and the maximum photoelectric conversion efficiency PCE is 35.59%.

[0064] In summary, the present invention relates to an asymmetric inner cavity regulated narrow linewidth vertical cavity surface emitting laser 10, the thickness of the expansion layer 5 is greater than the thickness of the P-type Bragg reflection layer 21, so that the effective cavity length in the vertical cavity surface emitting laser 10 is increased, and the line width of the vertical cavity surface emitting laser 10 is further reduced, while simplifying the optical path system of the vertical cavity surface emitting laser 10, improving the integration of the laser and reducing the volume of the vertical cavity surface emitting laser 10. The problem of the large line width of the existing vertical cavity surface emitting laser is solved, and the effective cavity length of the conventional vertical cavity surface emitting laser 10 design is significantly increased.

[0065] The above embodiment is only one implementation of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A narrow linewidth vertical cavity surface emitting laser controlled by an asymmetric cavity, characterized in that: The laser is provided with a first electrode, a P-type Bragg reflection unit, an oxidation restriction layer, an active layer, an expansion layer, an N-type Bragg reflection unit, a substrate and a second electrode in order from top to bottom. The P-type Bragg reflection unit includes a P-type Bragg reflection layer with a preset P-DBR pair number stacked, and the N-type Bragg reflection unit includes an N-type Bragg reflection layer with a preset N-DBR pair number stacked; the expansion layer is Al 0.9 Ga 0.1 As, the doping concentration of the extension layer is 2×10 18 cm -3 ; The thickness of the extended layer is in the range of 1-2 microns; the preset P-DBR logarithm is less than the preset N-DBR logarithm; the preset P-DBR logarithm ranges from 22 to 24, and the preset N-DBR logarithm ranges from 34 to 36; an oxidation hole is provided on the oxidation restriction layer, and the diameter of the oxidation hole is 3-4 microns; a gradient layer is sandwiched between adjacent P-type Bragg reflection layers in the P-type Bragg reflection unit and / or adjacent N-type Bragg reflection layers in the N-type Bragg reflection unit, and the gradient layer is Al x Ga 1-x As, Al x Ga 1-x The As component variation range is: x=0.9-0.12; the thickness of the gradient layer is 10-20 nm.

2. The narrow linewidth vertical cavity surface emitting laser controlled by an asymmetric intracavity according to claim 1, characterized in that: The P-type Bragg reflection layer is Al 0.9 Ga 0.1 As and Al 0.12 Ga 0.88 As, the doping concentration of the P-type Bragg reflector is 3×10 18 cm -3 .

3. The narrow linewidth vertical cavity surface emitting laser controlled by an asymmetric intracavity according to claim 1, characterized in that: The N-type Bragg reflection layer is Al 0.9 Ga 0.1 As and Al 0.12 Ga 0.88 As, the doping concentration of the N-type Bragg reflector is 2×10 18 cm -3 .

4. The narrow linewidth vertical cavity surface emitting laser controlled by an asymmetric intracavity according to claim 1, characterized in that: The first electrode and / or the second electrode is made of any one of gold, copper, graphite, silver or tin.

5. The method for preparing a narrow linewidth vertical cavity surface emitting laser controlled by an asymmetric inner cavity according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, epitaxially growing an N-type Bragg reflection unit, an extension layer, an active layer, an oxidation restriction layer and a P-type Bragg reflection unit on a substrate in sequence; S2. A first electrode is arranged on a side of the substrate away from the P-type Bragg reflection unit, and a second electrode is made on a side of the substrate away from the N-type Bragg reflection unit to obtain a vertical cavity surface emitting laser.

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