CN219535169U

CN219535169U - Large-oxidation-aperture vertical cavity surface emitting laser with high-temperature characteristic

Info

Publication number: CN219535169U
Application number: CN202320187662.9U
Authority: CN
Inventors: 王玉; 叶培飞; 丁杰; 李成; 张银桥; 叶伟民
Original assignee: Xiamen Yinke Qirui Semiconductor Technology Co ltd
Current assignee: Xiamen Yinke Qirui Semiconductor Technology Co ltd
Priority date: 2023-02-09
Filing date: 2023-02-09
Publication date: 2023-08-15
Anticipated expiration: 2033-02-09

Abstract

The utility model provides a large-oxidation aperture vertical cavity surface emitting laser with high temperature characteristic, which is formed by growing a metal organic chemical vapor deposition method on a GaAs substrate, and sequentially comprises a GaAs buffer layer, a first N-type DBR reflecting layer, a second N-type DBR reflecting layer, a third N-type DBR reflecting layer, a resonant cavity layer, a P-type DBR reflecting layer and an ohmic contact layer from bottom to top; wherein, the first pair of P-type DBRs above the resonant cavity is an oxide layer and is positioned at the node position of the optical field resonant wave. The utility model reduces the far field divergence angle by adding the high-order mode suppression cavity length to suppress the high-order transverse mode lasing on the basis of the epitaxial structure of the conventional single junction 1-lambda cavity length VCSEL. Meanwhile, in order to obtain better high-temperature characteristics, multiple AlAs layers with good heat conduction characteristics are inserted into the high-order mode inhibition cavity length, so that the high-temperature characteristics of the device are improved.

Description

Large-oxidation-aperture vertical cavity surface emitting laser with high-temperature characteristic

Technical Field

The utility model relates to the technical field of VCSELs of vertical cavity surface emitting lasers, in particular to a large-oxidation-aperture vertical cavity surface emitting laser with high-temperature characteristics.

Background

Compared with the traditional edge-emitting laser, the vertical cavity surface-emitting laser has the advantages of low threshold current, small volume, circular symmetrical light spots, easy optical fiber coupling, high beam quality, single longitudinal mode, easy surface emission integration and the like, so that the vertical cavity surface-emitting laser is rapidly developed in recent years and is widely applied to the fields of three-dimensional sensing such as face recognition, optical communication, laser radar, unmanned driving and the like.

The current optical communication InP base side emitting laser can control the divergence angles of a far field fast axis and a slow axis below 20 degrees by optimizing an epitaxial structure, and most single junction VCSEL far field divergence angles are about 25 degrees. A small divergence angle is advantageous in reducing energy loss and improving operation accuracy, and thus, a VCSEL having a small divergence angle has a certain advantage over a conventional VCSEL in many application fields.

GaAs-based VCSEL structures mostly use A/xGa 1-xAs with a high A l composition as the oxide aperture to limit current and optical field. The size of the oxidized aperture has a great influence on the laser performance. The adoption of the small oxidation aperture can inhibit the high-order transverse mode lasing so as to obtain a smaller far field divergence angle, but the small oxidation aperture can cause the increase of the resistance of the device, the self-heating effect of the device is obvious when the device works under a large current, and the high-temperature characteristic of the device is deteriorated. Therefore, there is a need to design a large-aperture VCSEL laser with a small far-field divergence angle.

Disclosure of Invention

The present utility model has been made in view of the above problems, and an object of the present utility model is to provide a low divergence angle vertical cavity surface emitting laser epitaxial structure that suppresses high order transverse mode lasing, reduces far field divergence angle, and has excellent high temperature characteristics.

In order to achieve the purpose, the utility model adds the high-order mode suppression cavity on the basis of the traditional single junction 1-lambda cavity long VCSEL epitaxial structure to suppress the high-order transverse mode lasing and reduce the far field divergence angle. Meanwhile, in order to obtain better high-temperature characteristics, a plurality of A lAs layers with good heat conduction characteristics are inserted into the high-order mode suppression cavity, so that the high-temperature characteristics of the device are improved.

The utility model provides a large-oxidation aperture vertical cavity surface emitting laser with high temperature characteristic, which is formed by growing a Metal Organic Chemical Vapor Deposition (MOCVD) method on a GaAs substrate, and sequentially comprises a GaAs buffer layer, a first N-type DBR reflecting layer, an N-type low-refractive-index-difference DBR reflecting layer, a resonant cavity layer, a P-type DBR reflecting layer and an ohmic contact layer from bottom to top; wherein, the first pair of P-type DBRs above the resonant cavity is an oxide layer and is positioned at the node position of the optical field resonant wave.

In any embodiment, the N-type low refractive index difference DBR reflecting layer comprises a second N-type DBR reflecting layer and a third N-type DBR reflecting layer to form a higher order mode suppression cavity.

In any embodiment, the DBR layers are each formed by alternately growing two different refractive index materials, and each optical thickness is equal to 1/4 lambda.

In any embodiment, the second N-type DBR reflective layer is comprised of N pairs of alas and A l GaAs l oop.

In any embodiment, the third N-type DBR reflective layer is comprised of m pairs A l GaAs and GaAs l oop.

In any embodiment, n can be set according to the actual requirements of performance and divergence angle, and the following conditions of high-order mode suppression cavity thickness are met, and m is 5.

In any embodiment, the optical thickness of each material of the second N-type DBR reflective layer is 1/4λ, and the optical thickness of each material of the third N-type DBR reflective layer is 1/4λ.

In any embodiment, the thickness of the higher order mode suppression cavity needs to meet the following conditions:

L＝2*(n _Al20GaAs d _Al20GaAs +n _GaAs d _GaAs )*5+2*(n _Al80GaAs d _Al80GaAs +n _AlAs d _AlAs )*N _DBR ＝Nλ

(N＝0、1、2…)

where L is the high order mode suppression cavity thickness, n is the material refractive index, d is the material thickness, NDBR is the second n-type DBR logarithm, and λ is the lasing wavelength.

In any embodiment, the high order mode suppression cavity thickness L is 1um-6um.

The beneficial effects of the utility model are as follows: according to the utility model, on the basis of the epitaxial structure of the conventional single junction 1-lambda cavity long VCSEL, the high-order mode suppression cavity is added to suppress high-order transverse mode lasing, so that the far field divergence angle is reduced. Meanwhile, in order to obtain better high-temperature characteristics, a plurality of A lAs layers with good heat conduction characteristics are inserted into the high-order mode suppression cavity, so that the high-temperature characteristics of the device are improved.

Compared with the conventional N-type DBR, the VCSEL structure with the multiple pairs of low-refractive-index-difference DBRs has the advantages that the refractive index difference of two layers of the DBR is smaller, the corresponding reflectivity is lower, the length of an optical field transmitted into the DBR is greatly increased, and the effective cavity length is increased equivalently. The transverse weak waveguide formed by oxidizing the oxidized hole in the VCSEL causes different loss of transverse modes of different modes in the propagation process, wherein the loss of a higher-order mode is larger than that of a fundamental mode, so that the farther the distance of propagation in the resonant cavity is, the larger the loss of the higher-order mode is, thereby inhibiting the lasing of the higher-order mode and playing a role in reducing the divergence angle.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some examples of the present utility model and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a large-aperture vertical cavity surface emitting laser with high temperature characteristics according to the present utility model.

Fig. 2 is a schematic diagram of another structure of a large-aperture vertical cavity surface emitting laser with high temperature characteristics according to the present utility model.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present utility model more apparent, the technical solutions of the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model, and it is apparent that the described embodiments are some embodiments of the present utility model, but not all embodiments. All other embodiments, based on the embodiments of the utility model, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the utility model. Thus, the following detailed description of the embodiments of the utility model, as presented in the figures, is not intended to limit the scope of the utility model, as claimed, but is merely representative of selected embodiments of the utility model.

In the description of the present utility model, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present utility model, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

In the description of the present utility model, the terms "upper," "middle," "side," "upper," "end," and the like refer to an orientation or positional relationship based on that shown in the drawings, merely for convenience of description and to simplify the description, rather than to indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the utility model.

At present, most single-junction VCSEL lasers realize single transverse mode lasing by reducing the diameter of an oxidation hole, but the small oxidation hole diameter can cause the increase of device resistance, and the self-heating effect is obviously increased in operation, so that the high-temperature characteristic is poor. The utility model adds the DBR structure with low refractive index difference on the basis of the traditional single-junction VCSEL, so that the effective cavity length of the VCSEL structure is long, the lasing of a high-order mode is restrained, and the far-field divergence angle is reduced. The structural design can ensure that the device has smaller far-field divergence angle on the basis of the large-oxidation aperture VCSEL.

In addition, when the device is operated in a high current mode, thermal prismatic effects due to local energy concentrations in the active region can also cause higher order modes to occur, as well as other electrical performance degradation. The AlAs material with higher heat transfer coefficient is used in the first group of low refractive index difference DBR (second N-type DBR reflecting layer), so that the situation that the device performance is deteriorated due to overhigh local temperature when the device works can be well relieved.

The utility model relates to a large-oxidation aperture vertical cavity surface emitting laser with high temperature characteristic, which is characterized in that a high-order mode suppression cavity formed by a second N-type DBR reflection layer and a third N-type DBR reflection layer group layer is inserted between a first N-type DBR reflection layer and a resonance cavity on the basis of the epitaxial structure of a traditional single junction 1-lambda cavity long VCSEL laser.

The lasing mode of a typical microcavity VCSEL laser comprises 5-6 transverse modes, for example: LP01, LP11, LP21, LP02, etc., wherein LP01 is the fundamental mode and the others are all the higher order modes, lateral light confinement by the oxidized aperture, there is a difference for the fundamental and higher order modes; the transverse limiting factor of the fundamental mode is larger than that of other high-order modes, so that the loss of the high-order modes is obviously larger than that of the fundamental mode in the process of light propagation of the high-order mode inhibition cavity, and the high-order modes are inhibited along with the increase of the propagation distance.

The high-order mode suppression cavity may be composed of bulk materials (such as GaAs or al xGa 1-xAs) having a forbidden bandwidth greater than the lasing wavelength, but the high-order mode suppression cavity of the present utility model is composed of two sets of different DBR reflective layers that differ from the first N-type DBR reflective layer and the P-type DBR reflective layer by alternating combinations of two layers of materials having a smaller difference in refractive index, respectively. The design reason is as follows: 1. compared with the first N-type DBR and the P-type DBR, the refractive index difference of the two layers of materials is smaller, the reflection effect on light is weaker, the light can travel deeper in the second DBR and the third DBR, and the effect of inhibiting a higher-order mode can be achieved; 2. the second and third DBRs are designed to supplement the reflection effect of the first N-type DBR, although the difference in refractive index is small, so that the number of growth pairs of the first N-type DBR reflection layer is reduced, and a certain production cost is saved.

The second N-type DBR reflective layer in the higher-order mode confinement cavity is formed by alternating A l GaAs/AlAs two layers, with the AlAs material having the best thermal conductivity in the AlxGa 1-xAs system. The design is to prevent the problem of degradation of high temperature characteristics and reliability of the laser caused by excessive concentration of heat generated by the MQW (multiple quantum well) during the operation of the laser. Due to the good heat conduction coefficient of the ai, the design can conduct heat generated in the working process of the laser to the whole core particle plane, and local temperature overheating is prevented.

The third N-type DBR reflective layer in the higher-order mode suppression cavity is composed of A l GaAs/GaAs two layers of material alternating, and the DBR reflective layer is composed of a material of a lower A l composition, in order to prevent the CP from being etched over-etched to the second N-type DBR reflective layer in the chip process, resulting in exposing the alas material, and in the oxidation of the later oxide holes, the alas layer is oxidized due to the very fast oxidation rate of alas, which easily leads to epitaxial layer delamination and reliability problems.

In addition, the thickness of the higher order mode suppression cavity needs to meet the following conditions:

(N＝0、1、2…)

The thickness of L is preferably controlled between 1um and 6um, and can be adjusted in the thickness range according to actual requirements.

Examples

Hereinafter, embodiments of the present utility model are described. The following examples are illustrative only and are not to be construed as limiting the utility model. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1:

the single-junction vertical cavity surface emitting laser VCSEL is formed by growing a Metal Organic Chemical Vapor Deposition (MOCVD) method on a GaAs substrate, and comprises a GaAs buffer layer, a first N-type DBR reflecting layer, a second N-type DBR reflecting layer, a third N-type DBR reflecting layer, a resonant cavity layer, a P-type DBR reflecting layer and an ohmic contact layer sequentially from bottom to top, wherein the DBR is formed by alternately growing two layers of materials with different refractive indexes, each optical thickness is equal to 1/4 lambda, and the first N-type DBR emitting layer and the P-type DBR reflecting layer are formed by alternately forming A l GaAs and GaAs two layers of materials. The oxide layer is positioned in the first pair of P-type DBRs above the resonant cavity and positioned at the node position of the optical field resonant wave.

The second N-type DBR reflection layer and the third N-type DBR reflection layer together form a high-order mode suppression cavity. The second N-type DBR is composed of N pairs of A lAs and A l GaAs l oop, and the optical thickness of the two layers is 1/4 lambda. The third N-type DBR is composed of 5 pairs A l GaAs and GaAs l oop, and the optical thickness of the two layers is 1/4 lambda.

Comparative example 1:

the single-junction vertical cavity surface emitting laser VCSEL is formed by growing a Metal Organic Chemical Vapor Deposition (MOCVD) method on a GaAs substrate, and sequentially comprises a GaAs buffer layer, an N-type DBR reflecting layer, a resonant cavity layer, a P-type DBR reflecting layer and an ohmic contact layer from bottom to top, wherein the DBR is formed by alternately growing two layers of materials with different refractive indexes, each optical thickness is equal to 1/4 lambda, and the first N-type DBR emitting layer and the P-type DBR reflecting layer are formed by alternately forming two layers of materials of Al90GaAs and GaAs. The oxide layer is positioned in the first pair of P-type DBRs above the resonant cavity and positioned at the node position of the optical field resonant wave.

As a result of analysis, the far field divergence angle of comparative example 1 was 27 °. The far field divergence angle of example 1 was optimized to 13 deg., significantly suppressing the lasing of the higher order modes.

The above description is only of the preferred embodiments of the present utility model and is not intended to limit the present utility model, and various modifications and variations may be made to the present utility model by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model should be included in the protection scope of the present utility model.

Claims

1. The high-oxidation aperture vertical cavity surface emitting laser with the high-temperature characteristic is characterized in that the high-oxidation aperture vertical cavity surface emitting laser is formed by growing on a GaAs substrate by adopting an MOCVD method, and sequentially comprises a GaAs buffer layer, a first N-type DBR reflecting layer, an N-type low-refractive index difference DBR reflecting layer, a resonant cavity layer, a P-type DBR reflecting layer and an ohmic contact layer from bottom to top; wherein, the first pair of P-type DBRs above the resonant cavity is an oxide layer and is positioned at the node position of the optical field resonant wave.

2. The large-aperture vertical cavity surface emitting laser having high temperature characteristics according to claim 1, wherein said N-type low refractive index difference DBR reflection layer comprises a second N-type DBR reflection layer and a third N-type DBR reflection layer forming a higher order mode suppression cavity.

3. The high temperature characteristic large oxide aperture vertical cavity surface emitting laser according to claim 2, wherein each of said DBR reflective layers is formed by alternately growing two layers of materials having different refractive indexes, and each optical thickness is equal to 1/4 λ.

4. The large-aperture vertical cavity surface emitting laser having high temperature characteristics according to claim 2, wherein said second N-type DBR reflecting layer is comprised of N pairs of AlAs and Al80GaAs loop.

5. The large-aperture vertical cavity surface emitting laser having high temperature characteristics according to claim 2, wherein said third N-type DBR reflecting layer is formed of m pairs of Al20GaAs and GaAs loop.

6. A large-aperture vertical cavity surface emitting laser according to claim 5, wherein m is 5.

7. The high temperature characteristic large aperture vertical cavity surface emitting laser as defined in claim 4, wherein said second N-type DBR reflection layer has a two-layer optical thickness of 1/4λ and said third N-type DBR reflection layer has a two-layer optical thickness of 1/4λ.

8. The large-aperture vertical cavity surface emitting laser having high temperature characteristics according to claim 2, wherein the thickness of said high-order mode suppression cavity is required to satisfy the following conditions:

L=2*(n _Al20GaAs d _Al20GaAs + n _GaAs d _GaAs )*5+2*（n _Al80GaAs d _Al80GaAs + n _AlAs d _AlAs ）*N _DBR = Nλ （N=0、1、2…）

where L is the high order mode suppression cavity thickness, n is the material refractive index, d is the material thickness, NDBR is the DBR logarithm, and λ is the lasing wavelength.

9. The large-aperture vertical cavity surface emitting laser having high temperature characteristics according to claim 8, wherein said high-order mode suppression cavity thickness L is 1um to 6um.