A vertical cavity surface emitting laser having a lateral structure and a method of manufacturing the same

Abstract

The application discloses a vertical cavity surface emitting laser with a transverse structure and a manufacturing method thereof. The vertical cavity surface emitting laser comprises a main cavity and N feedback cavities surrounding the periphery of the main cavity, and N>=2. The vertical cavity surface emitting laser has a high resistance layer at the longitudinal intersection of the upper Bragg emission mirror of the main cavity and the upper Bragg emission mirror of each feedback cavity, the high resistance layer is used for electrically isolating the main cavity and the feedback cavities, the high resistance layer is also used for improving the anti-waveguide refractive index at the intersection of the main cavity and the feedback cavities, and for determining the mode selection force for the laser to have a transverse mode. The vertical cavity surface emitting laser with the transverse structure has a transverse optical field limiting layer between the upper Bragg emission mirror and the active region. The main cavity is used for generating laser, and the laser is divided into a longitudinal mode and a transverse mode. The transverse mode is coupled into the feedback cavity under the joint action of the high resistance layer and the transverse optical field limiting layer, and is fed back to the main cavity along the transverse optical field limiting layer again, and then the photon-photon resonance effect occurs between the transverse mode in the main cavity and the transverse mode, so that the -3dB bandwidth is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor lasers, and particularly relates to a vertical cavity surface emitting laser with a lateral structure and a manufacturing method thereof. BACKGROUND

[0002] The vertical cavity surface emitting laser (VCSEL) has become the preferred light source for data center optical interconnection due to its good beam quality, high modulation rate, single longitudinal mode, low power consumption, easy on-chip testing and two-dimensional integration, and many other advantages. In recent years, VCSEL-based optical interconnection plays an increasingly important role in various networks from long-distance data transmission between data centers to short-distance transmission including machine rooms, inter-racks, inter-frames, inter-board, and ultra-short-distance transmission between chips.

[0003] With the continuous increase in the demand for bandwidth due to the global data explosion, the speed of Ethernet is advancing from 400 GbE to 800 GbE, and it is expected to break through the 1 TbE Ethernet technical barrier by 2025. To achieve ultra-high-speed Ethernet, the single-channel transmission rate evolves from 100 Gbit / s to 200 Gbit / s, which also puts forward higher requirements for the modulation rate of the VCSEL laser.

[0004] The modulation rate of a conventional direct modulation VCSEL laser is mainly determined by the intrinsic photon-carrier relaxation oscillation frequency, damping factor, external electrical parasitic cutoff frequency, and thermal effect. Researchers have proposed a large number of optimization schemes around the above factors. For example, for the intrinsic relaxation oscillation frequency and modulation bandwidth, foreign researchers propose to use InGaAs strained quantum wells instead of unstrained GaAs quantum wells in the active region, so that the differential gain of the quantum well is doubled, and methods such as using a half-wavelength cavity, reducing the photon volume, and placing an oxidation hole near the quantum well to enhance carrier confinement are used to achieve a modulation bandwidth of 29 GHz. For the parasitic effect and impedance characteristics of the VCSEL laser, some researchers propose to use a distributed Bragg reflection (DBR) modulation doping and double-oxidation photoelectric confinement structure to increase the parasitic cutoff frequency to 20 GHz. These studies have greatly improved the high-speed modulation characteristics of VCSELs. However, due to the intrinsic limitations of the carrier- photon resonance frequency, and the mutual restriction of the relaxation oscillation frequency and damping on the modulation bandwidth, it is difficult for the modulation frequency of the conventional structure VCSEL to break through 30 GHz. In terms of circuit, although through high-order optical signal modulation modes (such as pulse amplitude modulation PAM-4, PAM8) or short wavelength division multiplexing technology combined with equalization technology, a 28 GHz bandwidth VCSEL achieves a transmission rate of 200 Gb / s, however, the implementation of these technologies requires perfect matching of optical devices (VCSEL, PD) and driving, amplification circuits, as well as complex PCB board design, which undoubtedly increases the complexity and cost of the optical transmission chain.

[0005] Therefore, how to further efficiently improve the modulation frequency or modulation bandwidth of the VCSEL laser without increasing the complexity and cost of the optical transmission chain to meet the application of the next generation of optical interconnection is a great challenge for the VCSEL laser. SUMMARY

[0006] The purpose of the present application is to provide a vertical cavity surface emitting laser with a lateral structure and a manufacturing method thereof, to effectively improve the modulation frequency / modulation bandwidth of the VCSEL laser without increasing the complexity and cost of the optical transmission chain, thereby meeting the application of the next generation of optical interconnection.

[0007] In a first aspect, the present application provides a vertical cavity surface emitting laser with a transverse structure, comprising a main cavity and N feedback cavities surrounding the periphery of the main cavity, N>=2. The main cavity has an upper Bragg mirror and each feedback cavity has an upper Bragg mirror. The longitudinal intersection of the upper Bragg mirror of the main cavity and the upper Bragg mirror of each feedback cavity has a high resistance layer, which is used to electrically isolate the main cavity and each feedback cavity. The high resistance layer is also used to increase the anti-waveguide refractive index at the intersection of the main cavity and the feedback cavity, and to determine the mode selection force for the transverse mode of the laser. The vertical cavity surface emitting laser with a transverse structure has a transverse optical field limiting layer between the upper Bragg mirror and the active region. The main cavity is used to generate laser light, which is divided into longitudinal modes and transverse modes. A part of the transverse mode is coupled into the feedback cavity under the action of the high resistance layer and the transverse optical field limiting layer, is amplified and reflected in the feedback cavity, and is then fed back to the main cavity along the transverse optical field limiting layer. The transverse mode in the main cavity and the transverse mode fed back from the feedback cavity have a photon-photon resonance effect, thereby improving the -3dB bandwidth.

[0008] Compared with the prior art, the vertical cavity surface emitting laser with a transverse structure provided by the present application can break through the intrinsic limitation of carrier-photon resonance in the conventional structure of the electrically direct modulated VCSEL. The key is to use the optical coupling effect between the main cavity and the feedback cavity to improve the modulation bandwidth and transmission rate. That is, a part of the transverse mode of the laser generated in the main cavity leaks transversely along the transverse optical field limiting layer under the joint action of the high resistance layer and the transverse optical field limiting layer, and after multiple reflections of the transverse mode on the corresponding transverse optical field limiting layer of the feedback cavity, the transverse mode is fed back to the main cavity in the opposite direction. That is, the transverse mode fed back from the feedback cavity can be regarded as an external light source or an injected light source relative to the original transverse mode in the main cavity. When the frequency difference between the relaxation oscillation frequency and the frequency of the feedback cavity approaches the modulation frequency, another PPR peak appears on the small signal frequency response graph, thereby greatly improving the modulation bandwidth of the VCSEL laser.

[0009] In a second aspect, the present application also provides a manufacturing method of a vertical cavity surface emitting laser with a transverse structure, comprising the following steps:

[0010] Providing an epitaxial wafer;

[0011] Etching the epitaxial wafer to form a main cavity and N feedback cavities surrounding the periphery of the main cavity, N>=2;

[0012] Oxidizing the structure between the upper Bragg mirror and the active region of the vertical cavity surface emitting laser with a transverse structure to form a transverse optical field limiting layer;

[0013] Defining a proton implantation region at the longitudinal intersection of the upper Bragg mirror of the main cavity and the upper Bragg mirror of each feedback cavity;

[0014] Protons are injected into the proton injection area to form a high resistance layer.

[0015] Compared with the prior art, the method for manufacturing the vertical cavity surface emitting laser with a lateral structure provided by the present application has the same beneficial effects as the vertical cavity surface emitting laser with a lateral structure provided by the first aspect and / or any one of the implementation forms of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which are included to provide a further understanding of the present application and are incorporated in and constitute a part of this application, illustrate embodiments of the present application and together with the description serve to explain the present application. In the drawings:

[0017] Figure 1 A structure schematic diagram of a first vertical cavity surface emitting laser with a lateral structure provided by an embodiment of the present application;

[0018] Figure 2 A structure schematic diagram of a second vertical cavity surface emitting laser with a lateral structure provided by an embodiment of the present application;

[0019] Figures 3 to 13 A structure change diagram of the vertical cavity surface emitting laser with a lateral structure in a manufacturing process provided by an embodiment of the present application.

[0020] Reference signs:

[0021] a-main cavity, b-feedback cavity;

[0022] 100-lower electrode, 101-substrate, 102-lower buffer layer,

[0023] 103-lower Bragg reflector, 104-lower cladding layer, 105-lower heterojunction confinement layer,

[0024] 106-active region, 107-upper heterojunction confinement layer, 108-upper cladding layer,

[0025] 109-lateral optical field confinement layer, 110-upper Bragg reflector, 111-upper electrode,

[0026] 112-high resistance layer, 113-photoresist, 114-protection layer,

[0027] 115-metallic nickel, 116-BCB resin material. DETAILED DESCRIPTION

[0028] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0029] It should be noted that when an element is referred to as being "fixed" or "set" on another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or indirectly connected to the other element.

[0030] In addition, the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited. The meaning of "several" is one or more, unless otherwise explicitly specified and limited.

[0031] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0032] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] Reference is made to Figure 1 and Figure 2The embodiment of the present application provides a vertical cavity surface emitting laser with a transverse structure, which comprises a main cavity a and N feedback cavities b surrounding the periphery of the main cavity a, wherein N>=2 and N is a positive integer. The high resistance layer 112 is arranged at the longitudinal intersection of the upper Bragg mirror of the main cavity a and the upper Bragg mirror of each feedback cavity b, and the high resistance layer 112 is used for electrically isolating the main cavity a and each feedback cavity b. The high resistance layer 112 is also used for increasing the anti-waveguide refractive index at the intersection of the main cavity a and the feedback cavity b, and for determining the mode selection force for the transverse mode of laser. The vertical cavity surface emitting laser with the transverse structure has the transverse optical field limiting layer 109 between the upper Bragg mirror and the active region 106. The main cavity a is used for generating laser, and the laser is divided into longitudinal modes and transverse modes. The transverse modes are partially leaked to the feedback cavity b under the action of the high resistance layer 112 and the transverse optical field limiting layer 109, and then the transverse modes are fed back to the main cavity a along the transverse optical field limiting layer 109 after being amplified and reflected in the feedback cavity b, and then the photon-photon resonance effect occurs between the transverse modes in the main cavity a and the transverse modes in the feedback cavity b, so that the -3dB bandwidth is improved.

[0034] The high resistance layer 112 can realize the electrical isolation and optical conduction between the main cavity a and the feedback cavity b. That is, when an excitation signal with a certain frequency is applied to the main cavity a, the excitation signal is only applied to the active region 106 of the main cavity a, and the excitation signal cannot be applied to the active region 106 of the feedback cavity b under the block of the high resistance layer 112. That is, the active region 106 of the feedback cavity b cannot generate laser under the action of the excitation signal. The high resistance layer 112 can also increase the anti-waveguide refractive index at the longitudinal intersection of the main cavity a and the feedback cavity b under the condition of realizing the electrical isolation between the main cavity a and the feedback cavity b. That is, the transversely leaked transverse modes can be refracted into the feedback cavity b under the joint action of the high resistance layer 112 and the transverse optical field limiting layer 109, and the transverse modes are continuously reflected in the transverse optical field limiting layer 109 in the feedback cavity b. The high resistance layer 112 is also used for determining the mode selection force for the transverse modes, that is, the wavelength of the transverse modes leaked to the feedback cavity b is determined through the high resistance layer 112. In other words, the high resistance layer 112 selects the transverse modes with a certain wavelength to be leaked to the feedback cavity b, and cooperates with the setting of the quantum well in the active region 106, so that the wavelength of the laser finally emitted by the laser meets the preset requirement.

[0035] In a specific application, the active region 106 of the main cavity a is subjected to particle inversion to generate laser light under the action of the excitation signal. At this time, the laser light has a short lifetime, low intensity, multiple light wave modes, and poor directivity. Based on this, under the action of the upper Bragg reflector 110 and the lower Bragg reflector 103 of the main cavity a, the laser light is repeatedly oscillated and amplified, and is coupled into a bundle of longitudinal laser light propagating in the longitudinal direction. After the laser light is generated in the active region 106 of the main cavity a, the laser light leaks in the transverse direction in the transverse optical field limiting layer 109 due to the relatively high refractive index of the transverse optical field limiting layer 109. For the convenience of description, this is defined as a transverse mode. At this time, the transverse mode leaks in the transverse direction along the transverse optical field limiting layer 109 to each feedback cavity b. After the transverse mode is continuously reflected by inducing feedback in the feedback cavity b, the transverse mode is fed back to the main cavity a in the reverse direction along the transverse optical field limiting layer 109. Based on this, interference occurs between the original transverse mode in the main cavity a and the transverse mode fed back by the feedback cavity b. When the frequency of the excitation signal approaches the beat frequency between the two modes (i.e., the original transverse mode in the main cavity a and the transverse mode fed back to the main cavity a from the feedback cavity b), a significant photon-photon resonance effect occurs, and another PPR peak appears on the small signal frequency response graph, thereby greatly improving the modulation bandwidth of the VCSEL laser.

[0036] In addition, in order to achieve the above-mentioned transverse coupling (laser transverse leakage), the application adopts a transverse optical field limiting layer combined with a high-resistance layer 112 to form a reverse waveguide coupling structure of the main cavity a and the feedback cavity b, so that the coupling efficiency between the cavities is high. At the same time, the transverse reverse waveguide leakage wave coupling has mode selection force, which can reduce the threshold of the device, select the appropriate mode to achieve the maximum bandwidth expansion, and use the Bragg reflector slow light waveguide as the lateral light feedback cavity b, which can greatly shorten the feedback optical cavity length, thereby improving the compactness and integration of the VCSEL laser. In summary, the reverse waveguide coupling structure of the multiple feedback cavities b and the main light-emitting cavity can reduce the threshold, increase the photon-photon resonance strength, and improve the modulation characteristics of the device, i.e., improve the modulation bandwidth of the device.

[0037] Furthermore, in actual applications, the feedback cavities b can be integrally formed around the main cavity a to achieve optical feedback by using the feedback cavities b, which has the advantages of simple optical transmission chain and low cost compared with the prior art.

[0038] A vertical cavity surface emitting laser with a transverse structure can include a main cavity a, which can have four side surfaces (i.e., the main cavity a can be a hexahedral structure) and be symmetrical in twos. At this time, the number of feedback cavities b can be two, three, or four.

[0039] When the number of feedback cavities b is two, the two feedback cavities b are symmetrically distributed on the two sides of the main cavity a. At this time, the vertical cavity surface emitting laser composed of the main cavity a and the two feedback cavities b can be defined as a square vertical cavity surface emitting laser (see Figure 1 ).

[0040] When the number of feedback cavities b is three, two of the feedback cavities b are symmetrically distributed on the two sides of the main cavity a, and the third feedback cavity b is distributed on any one of the remaining two sides of the main cavity a. At this time, it can be defined as a square structure.

[0041] When the number of feedback cavities b is four, the four feedback cavities b are respectively distributed on the four sides of the main cavity a (see Figure 2 ).

[0042] The vertical cavity surface emitting laser with a cross-sectional structure composed of three feedback cavities b and one main cavity a, or four feedback cavities b and one main cavity a, can be defined as a petal-shaped structure.

[0043] In the case of multiple feedback cavities b, on the one hand, multiple feedback cavities b can receive transverse modes in different directions, and on the other hand, multiple feedback cavities b can be used to emit multiple feedback transverse modes from the main cavity a. Multiple feedback transverse modes can be superimposed in the main cavity a, so that the required feedback strength for PPR bandwidth expansion does not need to be very high.

[0044] Referring to Figure 1 , the length of the main cavity a can be less than or equal to the length of the feedback cavity b, and the lengths of the multiple feedback cavities b can be equal. The specific lengths of the main cavity a and the feedback cavity b can be determined according to actual needs, which are not specifically limited here. As an example, the length of the main cavity a can be 4um-7um, for example, 4um, 5um, 6um, 7um; the length of the feedback cavity b can be 4um-15um, for example, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um.

[0045] Referring to Figure 1 and Figure 2 , the multiple feedback cavities b can have equal widths, and the width of the main cavity a can be smaller than the width of the feedback cavity b. In this way, when the main cavity a is a short cavity, the single-mode light emission is good in unidirectionality because Δν=c / 2nL, that is, the shorter the L, the greater the interval between the modes, which is more conducive to single-mode light emission. In the case of equal lengths of the multiple feedback cavities b, it is convenient for layout design and subsequent process condition matching.

[0046] Referring to Figure 1 and Figure 2In order to further enhance the feedback intensity of the feedback cavity b to the transverse mode, a mirror layer can also be arranged at the end opposite to the main cavity a of each feedback cavity b, and the mirror layer comprises an oxidation limiting layer and a high reflection film layer. The high reflection film layer is arranged to enable the transverse mode entering the feedback cavity b to be completely fed back into the main cavity a. The oxidation limiting layer can be one of the transverse light field limiting layers 109, and the specific material is an AlGaAs layer. The Al content of the layer is relatively high compared with other layer structures, and the layer is more easily oxidized to form Al2O3 during subsequent wet oxidation.

[0047] Referring to Figure 1 and Figure 2 The high resistance layer 112 can be formed by a proton implantation process. The implanted protons can be H + As described above, the high resistance layer 112 is arranged at the longitudinal intersection of the upper Bragg mirror of the main cavity a and the upper Bragg mirror 110 of each feedback cavity b. The upper Bragg mirror 110 can be formed by stacking and arranging two AlxHGaAs / AlxLGaAs pairs having different refractive indices and electrical conductivity. In practical applications, a mask can be used to define a proton implantation area, and then a proton implantation process is applied to implant H + in the proton implantation area to form the high resistance layer 112 having a high resistance and a certain light reflection index, so as to realize electrical insulation and coherent coupling of light between the main cavity a and each feedback cavity b.

[0048] Referring to Figure 1 and Figure 2 The transverse light field limiting layer 109 can be an oxidation limiting layer formed by a wet oxidation process. The oxidation limiting layer has a high effective reflection rate, so that the transversely leaked laser light can be reflected in the transverse direction along the oxidation limiting layer to form a light transmission link emitted from the main cavity a, reflected by the feedback cavity b, and re-entered into the main cavity a, and to enhance the coupling strength between the main cavity a and the feedback cavity b. Specifically, the transverse mode in the feedback cavity b is coupled into the main cavity a in the transverse direction at the oxidation limiting layer. At this time, the effective refractive index of the main cavity a at the transverse intersection of the main cavity a and the feedback cavity b is 3% to 8%, for example, 3%, 4%, 5%, 6%, 7%, or 8%. The material of the oxidation limiting layer formed by the wet oxidation process can be AlxGa1-x As, where 0.97≤x≤1.

[0049] In order to more clearly understand the specific structure of the vertical cavity surface emitting laser with a transverse structure provided by the embodiments of the present application, specific embodiments will be described below. It should be understood that the following description is only for explanation and is not limiting.

[0050] Referring toFigure 1 and Figure 2 The vertical cavity surface emitting laser provided by the embodiment of the present application can sequentially include, from bottom to top, a lower electrode 100, a substrate 101, a lower buffer layer 102, a lower Bragg reflector 103, a lower cladding layer 104, a lower heterojunction confinement layer 105, an active region 106, an upper heterojunction confinement layer 107, an upper cladding layer 108, a transverse optical field confinement layer 109, an upper Bragg reflector 110, an upper electrode 111, and a high resistance layer 112. The above structure forms a square vertical cavity surface emitting laser with a lateral structure or a petal-shaped vertical cavity surface emitting laser with a lateral structure. That is, a main cavity a is formed at a position close to the middle of the above structure, and a feedback cavity b is formed at the periphery of the main cavity a.

[0051] Specifically, the lower electrode 100 can be an integrated lower electrode 100 formed by an electron beam evaporation deposition technology, i.e., the lower electrode 100 covers the substrate 101 at the main cavity a region and the feedback cavity b region. In other words, the main cavity a and the feedback cavity b share the lower electrode 100. The material of the lower electrode 100 can be Ni-Ge-Au, and the thickness of the lower electrode 100 can be 100 nm to 500 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm.

[0052] The substrate 101 can be an N-type doped substrate or a semi-insulating GaAs substrate. When the substrate 101 is an N-type doped substrate, the lower electrode 100 can be an N electrode, and the upper electrode 111 can be a P electrode.

[0053] When the substrate 101 is an N-type doped substrate, the lower buffer layer 102 can be an N-type doped buffer layer, which can be formed by metal organic chemical vapor deposition on the N-type doped substrate 101.

[0054] The lower Bragg reflector 103 can also be formed by metal organic chemical vapor deposition on the N-type doped buffer layer and alternately grown in sequence. When the substrate 101 is an N-type doped substrate, the lower Bragg reflector 103 is an N-type doped Bragg reflector. The number of layers of the lower Bragg reflector 103 is determined according to actual needs, which is not limited here.

[0055] When the substrate 101 is an N-type doped substrate, the lower cladding layer 104 is an N-type doped layer, and the upper cladding layer 108 is a P-type doped layer. Both the lower cladding layer 104 and the upper cladding layer 108 use AlxGaAs material with gradually changing aluminum components. The selection of the aluminum components in the AlxGaAs material makes the low-energy band gap end close to the heterojunction confinement layer band gap, and the high-energy band gap end close to the oxidation confinement high-aluminum layer band gap.

[0056] The upper heterojunction confinement layer 107 and the lower heterojunction confinement layer 105 have the same structure, and the materials of the upper heterojunction confinement layer 107 and the lower heterojunction confinement layer 105 are the same as the material of the barrier layer or have a band gap greater than the material of the barrier layer, and the materials of the upper heterojunction confinement layer 107 and the lower heterojunction confinement layer 105 are not doped.

[0057] The active region 106 can adopt a compressively strained quantum well structure of 3-9 layers stacked, and the compressively strained quantum well structure is arranged on the center of the standing wave in the main cavity a to improve the differential gain of the VCSEL laser and further improve the fundamental frequency.

[0058] When the substrate 101 is an N-type doped substrate, the lateral optical field confinement layer 109 can be a lateral optical field confinement layer 109 formed by processing a P-type doped oxide confinement layer by a wet oxidation process.

[0059] When the substrate 101 is an N-type doped substrate, the upper Bragg reflector 110 can be a P-type doped Bragg reflector. The number of layers of the lower Bragg reflector 103 is determined according to actual needs, which is not limited here. It needs to be further explained that the reflectivity of the lower Bragg reflector 103 is higher than that of the upper Bragg reflector 110, which is beneficial to the emission of laser from the top of the vertical cavity surface emitting laser.

[0060] When the substrate 101 is an N-type doped substrate, the upper electrode 111 can be a P electrode formed by an electron beam evaporation technology, and the material of the P electrode is Ti-Pt-Au. The thickness of the upper electrode 111 is 300-700 nm, for example, 300 nm, 400 nm, 500 nm, 600 nm or 700 nm. The upper electrode 111 can be a separate upper electrode 111, that is, the top of the main cavity a and the top of the feedback cavity b form P electrodes that are independent and insulated from each other. At this time, the separate electrodes can control the main cavity a and the feedback cavity b respectively, based on which the problem of uniformity of injected current and light waveguide loss in the feedback cavity b can be effectively solved, the phase control between units is realized, and the reverse coupling mode is formed.

[0061] In a second aspect, the embodiment of the present application further provides a manufacturing method of a vertical cavity surface emitting laser with a lateral structure, comprising the following steps:

[0062] S10, providing an epitaxial wafer, see 3, taking N-type doped GaAs substrate as an example (substrate in subsequent steps is N-type doped GaAs substrate), growing N-type doped buffer layer (one of lower buffer 102), N-type doped lower Bragg mirror layer (one of lower Bragg mirror 103), lower cladding layer 104, non-doped lower heterojunction confinement layer (one of lower heterojunction confinement layer 105), active layer (structure which becomes active region 106 later), non-doped upper heterojunction confinement layer (one of upper heterojunction confinement layer 107), upper cladding layer 108, P-type doped oxidation confinement layer (one of transverse optical field confinement layer 109), P-type doped upper Bragg mirror layer (one of upper Bragg mirror 110) and P-type heavily doped electrode contact layer (not shown in the figure) on substrate 101 in sequence by metal organic chemical vapor deposition (MOCVD).

[0063] S11, etching the epitaxial wafer to form main cavity a and N feedback cavities b around the periphery of the main cavity, N≥2. See Figure 4 , coating photoresist on the top end of the wafer and performing patterned processing on the photoresist to form a mask layer, which can be used to define the structure formation of the vertical cavity surface emitting laser with transverse structure, for example, the square or petal shape mentioned above. Etch P-type heavily doped electrode contact layer, P-type doped upper Bragg mirror layer, P-type doped oxidation confinement layer, upper cladding layer, non-doped upper heterojunction confinement layer, active layer in sequence from top to bottom under the mask of the mask layer, and further over-etch to the first pair of N-type doped lower Bragg mirror layer close to the active region in the three pairs of N-type doped lower Bragg mirror layer with Al component of 85%-90% in the high Al layer, exposing part of the surface of the N-type doped lower Bragg mirror layer. As another example, etching to the substrate to form Figure 1 and Figure 2 the structure mentioned above. At this time, it is convenient to dissipate heat of the vertical cavity surface emitting laser with transverse structure,

[0064] S12, oxidizing the transverse optical field confinement layer 109 between the upper Bragg mirror and the active region of the vertical cavity surface emitting laser. See Figure 5 , for example, wet oxidation is performed on the P-type doped oxidation confinement layer to make the oxidation confinement layer, i.e. the transverse optical field confinement layer 109 mentioned above.

[0065] S13, defining proton implantation area, which is located at the longitudinal intersection of the upper Bragg mirror of the main cavity and the upper Bragg mirror well of each feedback cavity. See Figure 6 and Figure 7A 3.5 μm layer of silicon dioxide (which can be defined as the protective layer 114) can be grown on the surface of the upper epitaxial wafer by plasma enhanced chemical vapor deposition (PECVD), and a 3000 metal nickel layer 115 can be sputtered as a mask, the proton implantation area can be defined by electron beam lithography technology, the nickel in the proton implantation area can be stripped off, and the silicon dioxide in the proton implantation area can be removed by ICP etching to define the proton implantation area.

[0066] S14, injecting protons into the proton implantation area to form a high-resistance layer 112. Referring to Figure 8 The H+ implantation is performed in the proton implantation area between the feedback cavity and the VCSEL main cavity by the proton implantation method. During the implantation, a multi-energy superposition implantation method is adopted, for example, the first implantation energy is 315 keV, and the second implantation energy is 250 keV, and the implantation dose of both times is 1E15 cm-2, which reduces the damage to the active region 106 (quantum well) and the surface conductive layer. After the implantation is completed, the silicon dioxide and nickel are removed by wet etching, and at this time, the high-resistance layer 112 is formed in the proton implantation area.

[0067] After step S14, the method for manufacturing the vertical cavity surface emitting laser further includes:

[0068] S15, depositing a protective layer 114 on the surface of the upper Bragg reflector. Referring to Figure 9 The silicon dioxide protective layer is deposited on the surface of the P-type heavily doped electrode contact layer.

[0069] S16, spin coating to form a BCB resin layer 116. Referring to Figure 10 The height of the mesa is about 3.5-3.8 um, which is measured by a step meter. The obtained wafer is spin coated by using the adhesive AP3000 combined with the 3022-57 BCB material, and is placed into an oven for curing to realize the planarization of the device.

[0070] S17, coating photoresist 113 on the surface of the BCB resin layer 116, removing the photoresist located on the surface of the upper Bragg reflector, and removing the BCB resin layer and the protective layer located on the surface of the upper Bragg reflector. Referring to Figure 11 and Figure 12 The BCB on the mesa is etched by using ICP etching with the photoresist 113 as a mask. The height is measured by a step meter after the etching process to ensure that the height difference of the mesa is less than 500 nm, thereby ensuring that the upper electrode 111 (which can be a P electrode) is well contacted in the subsequent lead-out.

[0071] S18, forming a split upper electrode on the position of the upper Bragg reflector corresponding to the main cavity and the feedback cavity. Referring to Figure 13The top electrode 111 is made on the top of the cylindrical mesa by electron beam evaporation technology, and the material of the top electrode 111 is Ti-Pt-Au with a thickness of 500 nm. Then, a SiN passivation layer with a thickness of 300 nm is deposited on the sidewall of the cylindrical mesa and the surface of the first distributed Bragg reflector around by PECVD technology.

[0072] S19, thinning the back surface of the substrate layer, and forming an integrated lower electrode on the back surface of the substrate layer. Referring to Figure 13 The substrate is thinned to 100 μm, and a lower electrode 100 is formed on the thinned GaAs substrate by depositing Ni-Ge-Au with a thickness of 300 nm by electron beam evaporation technology, and then performing rapid thermal annealing at 350 °C.

[0073] In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0074] The above description is merely specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which 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 vertical cavity surface-emitting laser with a transverse structure, characterized in that, The system includes a main cavity and N feedback cavities surrounding the main cavity, where N ≥ 2. A high-resistivity layer is provided at the longitudinal junction of the upper Bragg mirror in the main cavity and the upper Bragg mirror in each feedback cavity. This high-resistivity layer electrically isolates the main cavity from each feedback cavity. The high-resistivity layer also increases the refractive index of the anti-waveguide at the junction of the main cavity and the feedback cavities, and determines the mode selectivity for transverse modes of the laser. A mirror layer is provided at the end of each feedback cavity opposite the main cavity. The mirror layer includes an oxide confinement layer and an anti-reflection coating layer. The mirror layer enhances the feedback strength of the feedback cavity for transverse modes. The vertical cavity surface-emitting laser with a transverse structure has a transverse optical field confinement layer between the upper Bragg mirror and the active region. The main cavity is used to generate laser light, which is divided into longitudinal mode and transverse mode. Under the action of the high-resistivity layer and the transverse optical field confinement layer, a portion of the transverse mode is coupled to the feedback cavity. After being amplified and reflected in the feedback cavity, it is fed back to the main cavity along the transverse optical field confinement layer and then interacts with the transverse mode in the main cavity to generate a photon-photon resonance effect, thereby improving the -3dB bandwidth.

2. The vertical cavity surface-emitting laser with a transverse structure according to claim 1, characterized in that, The vertical surface-emitting laser with a transverse structure can be either a square structure or a petal-shaped structure.

3. The vertical cavity surface-emitting laser with a transverse structure according to claim 2, characterized in that, The main cavity has a hexahedral structure. When the vertical surface laser with a transverse structure has a square structure, it includes two feedback cavities, which are symmetrically distributed on both sides of the main cavity. When the vertical surface-emitting laser with a transverse structure is a petal-shaped structure, it includes three feedback cavities, two of which are symmetrically distributed on both sides of the main cavity, and the third feedback cavity is distributed on any one of the remaining two sides of the main cavity; or, it includes four feedback cavities, which are respectively distributed on the four sides of the main cavity.

4. The vertical cavity surface-emitting laser with a transverse structure according to claim 1, characterized in that, The high-resistivity layer is formed through a proton implantation process, with the implanted protons being H. + ; and / or, the transverse light field confinement layer is an oxide confinement layer, which is an oxide confinement layer formed by a wet oxidation process.

5. The vertical cavity surface-emitting laser with a transverse structure according to claim 1, characterized in that, When the transverse optical field confinement layer is an oxide confinement layer, the material of the oxide confinement layer is AlxGa1-xAs, where 0.97 ≤ x ≤ 1; and / or, The transverse mode in the feedback cavity is fed back into the main cavity by the transverse optical field confinement layer. At this time, the effective reflectivity of the transverse mode at the transverse junction of the main cavity and the feedback cavity is 3% to 8%.

6. The vertical cavity surface-emitting laser with a transverse structure according to claim 1, characterized in that, The bottom electrodes of the main cavity and the feedback cavity are integral electrodes; the top electrodes of the main cavity and the feedback cavity are separate electrodes.

7. The vertical cavity surface-emitting laser with a transverse structure according to claim 1, characterized in that, The length of the main cavity is less than or equal to the length of the feedback cavity, and the lengths of the multiple feedback cavities are equal; the length of the main cavity is 4µm to 7µm; the strength of the feedback cavity is 4µm to 15µm.

8. The vertical cavity surface-emitting laser with a transverse structure according to claim 1, characterized in that, The main cavity and the feedback cavity are an integrated structure, which includes, from bottom to top, a lower electrode, a substrate, a lower Bragg mirror, an active region, a lateral light field confinement layer, an upper Bragg mirror, and an upper electrode. The high-resistivity layer is disposed on the longitudinal section of the upper Bragg mirror and is located at the longitudinal junction of the main cavity and each feedback cavity.

9. The vertical cavity surface-emitting laser with a transverse structure according to claim 8, characterized in that, The substrate and the lower Bragg mirror further include a lower buffer layer; and / or, the lower Bragg mirror and the active region, from bottom to top, include a lower cladding layer and a lower heterojunction confinement layer; and / or, the active region and the upper Bragg mirror, from bottom to top, include an upper heterojunction confinement layer and an upper cladding layer; and / or, the upper electrode is made of Ti-Pt-Au and has a thickness of 300 nm to 700 nm; and / or, the lower electrode is made of Ni-Ge-Au and has a thickness of 100 nm to 500 nm; and / or, the substrate is either an N-type doped substrate or a semi-insulating GaAs substrate.

10. The vertical cavity surface-emitting laser with a transverse structure according to claim 9, characterized in that, The reflectivity of the lower Bragg mirror is greater than or equal to that of the upper Bragg mirror; both the lower and upper Bragg mirrors are formed by stacking two AlxHGaAs / AlxLGaAs pairs with different refractive indices. The upper heterojunction confinement layer and the lower heterojunction confinement layer have the same structure. The materials of the upper heterojunction confinement layer and the lower heterojunction confinement layer are the same as the material of the barrier layer, or the band gap is larger than that of the material of the barrier layer, and the materials of the upper heterojunction confinement layer and the lower heterojunction confinement layer are undoped. At this time, both the lower cladding and the upper cladding are made of AlxGaAs material with a gradually changing aluminum composition. The choice of aluminum composition in AlxGaAs material makes it close to the band gap of the heterojunction confinement layer at the low energy band gap end and close to the band gap of the oxide-confined high-alumina layer at the high energy band gap end.

11. The vertical cavity surface-emitting laser with a transverse structure according to claim 1, characterized in that, The active region employs 3 to 9 stacked compressive strain quantum well structures, which are disposed on the central antinode of the standing wave present in the main cavity.

12. A method for manufacturing a vertical cavity surface-emitting laser with a transverse structure, characterized in that, Includes the following steps: Provide epitaxial wafers; The epitaxial wafer is etched to form a main cavity and N feedback cavities surrounding the main cavity, where N≥2; A reflective mirror layer is formed at one end of each feedback cavity opposite to the main cavity; the reflective mirror layer includes an oxide confinement layer and an anti-reflection film layer; the reflective mirror layer is used to enhance the feedback strength of the feedback cavity for the transverse mode; Oxidation is applied to the structure between the upper Bragg mirror and the active region of the vertical cavity surface-emitting laser with a transverse structure to form a transverse optical field confinement layer. Define a proton injection region located at the longitudinal junction of the upper Bragg mirror of the main cavity and the upper Bragg mirror of each feedback cavity; Protons are injected into the proton injection region to form a high-resistivity layer.

13. The method for manufacturing a vertical cavity surface-emitting laser with a transverse structure according to claim 12, characterized in that, The epitaxial wafer, from bottom to top, includes at least a substrate layer, a lower buffer layer, a lower Bragg mirror layer, a lower cladding layer, a lower heterojunction confinement layer, an active layer, an upper heterojunction confinement layer, an upper cladding layer, a lateral beam confinement layer, and an upper Bragg mirror layer. The epitaxial wafer is etched to form a main cavity and N feedback cavities surrounding the main cavity, where N ≥ 2, including: The structural shapes of the main cavity and the feedback cavity are determined, and the upper Bragg reflector layer, the lateral light field confinement layer, the upper cladding layer, the upper heterojunction confinement layer, the active layer, the lower heterojunction confinement layer, and part of the lower cladding layer are etched from top to bottom according to the structural shapes.

14. The method for manufacturing a vertical cavity surface-emitting laser with a transverse structure according to claim 13, characterized in that, Defining the proton injection region includes forming a mask layer on top of the upper Bragg mirror formed by etching the upper Bragg mirror layer; Patterned mask layers are used to define the proton injection region; Injecting the remaining internally injected protons into the protons to form a high-resistivity layer includes: The multi-energy superposition injection method injects protons into the proton injection region. The first injection energy was 315 keV, the second injection energy was 250 keV, and the injection dose was 1E15cm for both injections. -2 .

15. The method for manufacturing a vertical cavity surface-emitting laser with a transverse structure according to claim 13, characterized in that, After injecting protons into the proton injection region to form a high-resistivity layer, the method for manufacturing the vertical cavity surface-emitting laser with a lateral structure further includes: A protective layer is deposited on the surface of the upper Bragg mirror; Spin coating to form a BCB resin layer; A photoresist layer is coated on the surface of the BCB resin layer; Remove the photoresist layer located on the surface of the upper Bragg mirror; Remove the BCB resin layer and protective layer located on the surface of the upper Bragg mirror; A split upper electrode is formed at the position of the upper Bragg reflector corresponding to the main cavity and the feedback cavity; A protective layer is deposited on the surface of the upper electrode; The back side of the substrate is thinned to form an integral lower electrode on the back side of the substrate.

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