A single-mode high-power vertical cavity surface emitting laser structure and a manufacturing method thereof

Abstract

The application discloses a single-mode high-power vertical cavity surface emitting laser structure and a manufacturing method thereof, and the laser comprises, from bottom to top, a substrate layer, a lower N-type DBR, an active region, an asymmetric oxidation confinement layer, a space layer, an upper P-type DBR and a surface relief structure; the substrate layer and the lower N-type DBR form a first partial elliptic cylinder; the active region, the asymmetric oxidation confinement layer and the space layer form a second partial elliptic cylinder; the upper P-type DBR and the surface relief structure form a third partial elliptic cylinder; a negative electrode is arranged at both ends of a long axis of the first partial elliptic cylinder; a positive electrode is arranged at both ends of a short axis of the second partial elliptic cylinder; and the negative electrode and the positive electrode form an intra-cavity asymmetric electrode structure. The application improves the current injection efficiency, the optical coupling efficiency, the single-mode stability and the controllability of the device output wavelength of the device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor lasers, and particularly relates to a single-mode high-power vertical-cavity surface-emitting laser structure and a manufacturing method thereof. BACKGROUND

[0002] As a new emerging semiconductor laser technology, vertical-cavity surface-emitting lasers (VCSELs) have proven their significant advantages in multiple fields. VCSELs are widely used in optical communication, sensors, 3D sensing technologies such as facial recognition, optical interconnects, and laser radars, etc. due to their compact structure, low power consumption, fast modulation speed, and cost-effectiveness. Compared with traditional edge-emitting lasers, VCSELs have a unique feature of emitting light beams in a direction perpendicular to the substrate, which makes it easier to couple with optical fibers and suitable for array applications, thus playing a key role in integrated optical systems.

[0003] Despite the above advantages of VCSEL technology, there are still some technical challenges in existing designs. In particular, in terms of mode control, polarization stability, and beam quality, traditional VCSEL designs face some limitations. In the current injection region, the unevenness of the current and light field distribution around the active layer is the main reason for the decrease in laser efficiency, mode instability, and the increase in laser beam divergence angle. To solve these problems, the oxidation confinement layer technology is widely used. By oxidizing high-aluminum component materials such as AlGaAs, a transverse confinement structure is formed, which can effectively control the distribution of current and light field, thereby improving the efficiency of VCSELs.

[0004] However, existing oxidation confinement layers usually adopt symmetric circular or elliptical structures, which still cannot fully meet the performance optimization requirements in certain application scenarios, especially when increasing the modulation bandwidth and reducing the oxidation aperture to improve the VCSEL rate, the challenges of optical loss and thermal management problems are encountered. SUMMARY

[0005] To solve the above technical problems, the present application provides a single-mode high-power vertical-cavity surface-emitting laser structure and a manufacturing method thereof to solve the problems existing in the prior art.

[0006] To achieve the above purpose, in a first aspect, the present application provides a single-mode high-power vertical-cavity surface-emitting laser structure, comprising:

[0007] a substrate layer, a lower N-type DBR, an active region, an asymmetric oxidation confinement layer, a space layer, an upper P-type DBR, and a surface relief structure are sequentially arranged from bottom to top.

[0008] The substrate layer, the lower N-type DBR form a first partial elliptic cylinder; the active region, the asymmetric oxidation confinement layer, the space layer form a second partial elliptic cylinder; the upper P-type DBR, the surface relief structure form a third partial elliptic cylinder.

[0009] The negative electrode is arranged at the two ends of the long axis of the first partial elliptic cylinder; the positive electrode is arranged at the two ends of the short axis of the second partial elliptic cylinder; the negative electrode and the positive electrode form an intra-cavity asymmetric electrode structure.

[0010] Preferably, the first partial elliptic cylinder, the second partial elliptic cylinder and the third partial elliptic cylinder are all composed of two ellipses with the same short axis and different long axis, and are designed as coaxial elliptic cylinders.

[0011] Preferably, the asymmetric oxidation confinement layer is composed of two ellipses with the same short axis and different long axis.

[0012] Preferably, the space layer is optimized in parasitic resistance by doping modulation.

[0013] Preferably, the active region includes a plurality of active regions, each of which is formed by a plurality of pairs of quantum wells and well barriers stacked alternately.

[0014] Preferably, the surface relief structure is formed by deposition and etching on the top of the laser structure.

[0015] Preferably, the intra-cavity asymmetric electrode adopts asymmetric current injection.

[0016] Preferably, the material of the intra-cavity asymmetric electrode is Ti or Pt.

[0017] In a second aspect, the application further provides a manufacturing method of a single-mode high-power vertical cavity surface emitting laser structure, comprising the following steps:

[0018] The lower N-type DBR is epitaxially grown from bottom to top on the substrate layer by molecular beam epitaxy or metal organic chemical vapor deposition, to form a first partial elliptic cylinder;

[0019] The active region and the oxidation confinement layer are epitaxially grown on the first elliptic cylinder to form an asymmetric oxidation confinement layer, the space layer is epitaxially grown, and a second partial elliptic cylinder is formed;

[0020] The third partial elliptic cylinder is continuously epitaxially grown, including the upper P-type DBR;

[0021] Depositing negative electrodes on both long axis ends of the first pro-elliptical cylinder and positive electrodes on both short axis ends of the second pro-elliptical cylinder to form intra-cavity asymmetric electrodes;

[0022] Depositing and etching a relief structure on the top of the laser structure.

[0023] Compared with the prior art, the present application has the following advantages and technical effects:

[0024] The present application provides a single-mode high-power vertical cavity surface emitting laser structure, comprising: a substrate layer, a lower N-type DBR, an active region, an asymmetric oxidation confinement layer, a space layer, an upper P-type DBR, and a surface relief structure arranged in sequence from bottom to top; wherein the substrate layer and the lower N-type DBR form a first pro-elliptical cylinder; the active region, the asymmetric oxidation confinement layer, and the space layer form a second pro-elliptical cylinder; the upper P-type DBR and the surface relief structure form a third pro-elliptical cylinder; a negative electrode is arranged at both ends of the long axis of the first pro-elliptical cylinder; a positive electrode is arranged at both ends of the short axis of the second pro-elliptical cylinder; and the negative electrode and the positive electrode form an intra-cavity asymmetric electrode structure.

[0025] The present application adopts a pro-elliptical mesa design of an asymmetric oxidation confinement layer, sets a space layer near the active region, optimizes current injection, adopts a full-semiconductor intra-cavity asymmetric electrode structure, introduces a relief structure at the light output of the upper DBR, effectively realizes precise control of current injection and light field through the asymmetric pro-elliptical oxidation confinement layer, suppresses the excitation of high-order modes, strengthens the mode coupling effect, significantly improves the modulation characteristics, single-mode stability, and output efficiency of the device, and optimizes the heat dissipation performance of the device, which is helpful to improve the running stability under high power.

[0026] The present application improves single-mode output power through the relief structure, significantly reduces reflection loss by improving beam coupling efficiency, improves optical output power and overall coupling efficiency, and especially exhibits excellent performance in fiber coupling applications. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of this application, and of which specific embodiments will be described, are illustrated in the drawings, from which:

[0028] Figure 1 A cross-sectional view of a device structure according to an embodiment of the present application;

[0029] Figure 2 A top view of a device structure according to an embodiment of the present application;

[0030] Wherein, 100, substrate layer; 200, lower N-type DBR; 300, negative electrode; 400, active region; 500, asymmetric oxidation confinement layer; 600, space layer; 700, positive electrode; 800, upper P-type DBR; 900, surface relief structure. DETAILED DESCRIPTION

[0031] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0032] It should be noted that the steps shown in the flowchart of the drawings can be executed in a computer system such as a group of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in a different order.

[0033] As shown in the drawings, Figure 1 The present embodiment provides a single-mode high-power vertical cavity surface emitting laser structure, comprising:

[0034] From bottom to top, it is a first partial elliptical mesa GaAs substrate 100, a lower N-type DBR 200, a negative electrode 300 distributed on the first elliptical mesa, a second partial elliptical mesa containing an active region 400, an asymmetric oxidation confinement layer 500, a space layer 600, a positive electrode 700 distributed on the second partial elliptical mesa, a third partial elliptical mesa containing an upper P-type DBR 800 and a surface relief structure 900 formed by etching. The space layer 600 is at the top end of the active region 400. The intra-cavity asymmetric electrode is composed of the negative electrode 300 distributed on the first partial elliptical mesa and the positive electrode 700 distributed on the second partial elliptical mesa. The negative electrode for injecting electrons is placed at both ends of the long axis of the lower N-type DBR 200 elliptical mesa, and the positive electrode for injecting holes is placed at both ends of the short axis in the space layer of the second partial elliptical mesa. This structure improves the single-mode stability, output efficiency and overall coupling efficiency of the device, optimizes the heat dissipation performance of the device and realizes the stable control of the light emitting wavelength.

[0035] Figure 2Fig. 1 is a schematic top view of the laser structure according to the present application. As an innovative embodiment, the overall structure of the device is a non-symmetrical elliptical multi-mesa structure. The substrate 100 and the lower N-type DBR 200 form a first non-symmetrical elliptical cylinder. The first non-symmetrical elliptical mesa is composed of two half-elliptical mesas with the same short axis and different long axes.

[0036] The active region 400, the oxidation confinement layer 500 and the space layer 600 form a second non-symmetrical elliptical cylinder. The second non-symmetrical elliptical cylinder is also composed of two half-elliptical mesas with the same short axis and different long axes. The third elliptical mesa is composed of the upper P-type DBR 800 and the surface relief structure 900. The first, second and third non-symmetrical elliptical cylinders are designed as coaxial elliptical cylinders, which optimizes the heat dissipation capacity of the device. The shaded part on the first elliptical mesa is the negative electrode 300, and the shaded part on the second elliptical mesa is the positive electrode 700.

[0037] As an innovative embodiment, the surface relief structure 900 is used to improve the light coupling efficiency of the device. The non-elliptical multi-mesa and the intra-cavity asymmetric electrode adopt asymmetric current injection, which improves the device heat dissipation capacity, carrier recombination efficiency and mode stability.

[0038] Specifically, the active region includes a plurality of active regions, which is greater than or equal to 2, but not limited to 3, 4, 5, etc., and each active region is formed by a plurality of pairs of quantum wells and well barriers stacked alternately.

[0039] As an additional embodiment, the laser structure includes a specific photolithography and wet oxidation technology after epitaxial growth, forming a non-symmetrical oxidation confinement non-symmetrical elliptical mesa. The non-symmetrical elliptical mesa is composed of two half-elliptical mesas with the same short axis and different long axes. Compared with the symmetrical elliptical oxidation confinement layer, the non-symmetrical elliptical oxidation confinement layer can more effectively realize current injection and precise control of the optical field. At the same time, by adjusting the appropriate non-symmetrical elliptical oxidation aperture, the single mode stability and output efficiency of the device can be greatly affected. At the same time, this design can also make up for the shortcomings of the symmetrical oxidation confinement elliptical mesa in heat dissipation performance, which helps to improve the running stability under high power.

[0040] As an increased embodiment, by setting a space layer on the oxidation layer, by modulating the doped space layer, the parasitic resistance is optimized, and the parasitic cut-off frequency is improved. By combining the design of the intra-cavity electrode of the partial elliptical multi-mesa, the asymmetric current injection is adopted, the phenomenon of carrier congestion is reduced, the injected holes and electrons are effectively combined, the current distribution is uniform, and more current is injected into the active region, thereby improving the light emitting efficiency and the light output power of the device, and improving the heat dissipation capacity and polarization stability of the device, which is beneficial to the polarization of the emitted light in the vertical current direction. The heat dissipation capacity, carrier recombination efficiency and mode stability of the device are improved. Deposition and etching of the relief structure on the upper DBR can improve the single-mode output light power, improve the coupling efficiency of the light beam, and at the same time improve the overall coupling efficiency.

[0041] In summary, the embodiment proposes to form an asymmetrically oxidized and limited elliptical mesa by epitaxial growth, etching, and oxidation, and then continue to epitaxially grow a space layer, combine the intra-cavity electrode of the partial elliptical multi-mesa, and epitaxially grow an upper DBR, and deposit and etch a relief structure for the VCSEL structure laser structure. The purpose is to use the asymmetrically oxidized and limited partial elliptical mesa to improve the effective current injection efficiency of the device and further control the optical field, and at the same time improve the single-mode stability of the device. The thickness and refractive index of the space layer are used to effectively control the cavity length, thereby further effectively controlling the output wavelength of the device. By combining the design of the intra-cavity electrode of the partial elliptical multi-mesa, the asymmetric current injection is adopted, and the heat dissipation capacity, carrier recombination efficiency and mode stability of the device are improved. The relief structure formed by etching is used to improve the light coupling efficiency of the device, and the overall performance of the device is improved.

[0042] The beneficial effects of the embodiment are:

[0043] The embodiment discloses a single-mode high-power vertical cavity surface emitting laser structure, which aims to use the asymmetrically oxidized and limited layer, the epitaxially formed space layer, the elliptical multi-mesa intra-cavity asymmetric electrode, and the relief structure etched and grown on the P-type upper DBR to improve the current injection efficiency, the light coupling efficiency, the single-mode stability, and the control of the output wavelength of the device, improve the temperature performance and heat management of the device under high power, and thereby optimize the overall performance of the laser.

[0044] Embodiment two

[0045] The embodiment provides a manufacturing method of a single-mode high-power vertical cavity surface emitting laser structure, which specifically comprises:

[0046] S1, on the GaAs substrate 100, by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD) technology, the lower N-type DBR 200 is epitaxially grown from bottom to top, and then etched to form the first partial elliptical mesa.

[0047] The specific method is to use dry etching to etch the material according to the anisotropy of the etching rate of the material, and the direction with faster etching rate is designed as the short axis of the elliptical shape, and the direction with slower etching rate is designed as the long axis part of the elliptical shape, so that the etching aperture can obtain a better circular mode.

[0048] S2, epitaxially grow the active region 400 and the AlGaAs oxidation confinement layer 500 on the first elliptical mesa, and oxidize the same to form a partial elliptical oxidation hole. Next, epitaxially grow the space layer 600. And form the basis of the second partial elliptical mesa.

[0049] The second partial elliptical mesa is composed of two ellipses with the same short axis and different long axis, so that the current and light field can be more accurately controlled in this area. This splicing design not only can further optimize the distribution of current and ensure that the current is concentrated in the active region, but also can improve the mode control of laser and avoid the occurrence of unstable or asymmetric distribution of laser mode.

[0050] S3, continue to epitaxially grow the third layer of partial elliptical mesa structure, the upper P-type DBR 800, and deposit the negative electrode 300 on the two long axis ends of the first partial elliptical mesa and the positive electrode 700 on the two short axis ends of the second partial elliptical mesa, and the electrode material is Ti or Pt, thereby forming an intra-cavity asymmetric electrode.

[0051] Combined with the partial elliptical multi-mesa structure, and because the hole mobility is smaller than the electron mobility, the above electrode structure can be used to stabilize the polarization and make the injected holes and electrons effectively recombine, reduce the carrier congestion phenomenon, and make the current distribution uniform, so that more current is injected into the active region, thereby improving the light emitting efficiency, optical output power and mode stability of the device. At the same time, through the alternating arrangement of high and low refractive index materials, the upper P-type DBR 800 and the lower N-type DBR 200 together realize the effect of high reflectivity, improve the light feedback efficiency and reduce the intra-cavity loss.

[0052] S4, deposit and etch the relief structure 900 on the top of the device.

[0053] The introduction of the relief structure improves the single-mode output power, and at the same time improves the coupling efficiency of the light beam and improves the overall optical output power of the device.

[0054] Overall, the VCSEL structure of the embodiment effectively optimizes current injection, heat dissipation and mode stability by the two mesa design and the application of the asymmetric oxidation confinement layer and the asymmetric electrode in the cavity, and improves the single-mode output power. The structure overcomes the thermal effect problem of the traditional VCSEL in high-power application, and significantly improves the light output quality and reliability of the device.

[0055] The above merely provides the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical range disclosed by the present application can be easily thought by those skilled in the art, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A single mode high power vertical cavity surface emitting laser structure, characterized by, The laser structure comprises: a substrate layer, a lower N-type DBR, an active region, an asymmetric oxidation confinement layer, a space layer, an upper P-type DBR, and a surface relief structure arranged in sequence from bottom to top; wherein the substrate layer and the lower N-type DBR form a first partial elliptic cylinder; the active region, the asymmetric oxidation confinement layer, and the space layer form a second partial elliptic cylinder; the upper P-type DBR and the surface relief structure form a third partial elliptic cylinder; a negative electrode is arranged at the two ends of the long axis of the first partial elliptic cylinder; a positive electrode is arranged at the two ends of the short axis of the second partial elliptic cylinder; the negative electrode and the positive electrode form an intra-cavity asymmetric electrode structure; the first partial elliptic cylinder, the second partial elliptic cylinder, and the third partial elliptic cylinder are each composed of two ellipses with the same short axis and different long axes, and are designed as coaxial elliptic cylinders; the asymmetric oxidation confinement layer is composed of two ellipses with the same short axis and different long axes.

2. The laser structure of claim 1, wherein: the space layer is modulated in doping to optimize parasitic resistance.

3. The laser structure of claim 1, wherein: the active region comprises a plurality of active regions, each of which is formed by a plurality of pairs of quantum wells and well barriers stacked alternately.

4. The laser structure of claim 1, wherein: the surface relief structure is formed by deposition and etching on the top of the laser structure.

5. The laser structure of claim 1, wherein: the intra-cavity asymmetric electrode adopts asymmetric current injection.

6. The laser structure of claim 1, wherein: the material of the intra-cavity asymmetric electrode is Ti or Pt.

7. The method of fabricating a single mode high power vertical cavity surface emitting laser structure according to any of claims 1 to 6, characterized in that The method comprises the following steps: a lower N-type DBR is epitaxially grown on a substrate layer from bottom to top by a molecular beam epitaxy or a metal organic chemical vapor deposition method, to form a first partial elliptic cylinder; an active region and an oxidation confinement layer are epitaxially grown on the first partial elliptic cylinder to form an asymmetric oxidation confinement layer, a space layer is epitaxially grown, and a second partial elliptic cylinder is formed; a third partial elliptic cylinder, including an upper P-type DBR, is continuously epitaxially grown; a negative electrode is deposited on the two long axis ends of the first partial elliptic cylinder, and a positive electrode is deposited on the two short axis ends of the second partial elliptic cylinder to form an intra-cavity asymmetric electrode; a relief structure is deposited and etched on the top of the laser structure.

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