Semiconductor lasers, optical transmitter components and optical modules

Abstract

The embodiments of the present application relate to a semiconductor laser, an optical emission component, and an optical module. The semiconductor laser includes a substrate; a bottom reflector structure disposed on the substrate; an active layer disposed on the bottom reflector structure; a top reflector structure disposed on the active layer, wherein the top reflector structure and the bottom reflector structure define a resonant cavity; and a photon lifetime control layer disposed on the top reflector structure, wherein the photon lifetime control layer is configured to control the photon lifetime of the resonant cavity. The above-mentioned scheme of the present application can realize photon lifetime control of the semiconductor laser, and can effectively improve the relaxation oscillation frequency of the semiconductor laser.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of semiconductor laser technology, and in particular to semiconductor lasers, light emitting components, and optical modules. Background Art

[0002] Currently, data centers have become the fundamental carriers of new communication networks such as 5G and the Internet of Things, as well as the internet, cloud computing, and artificial intelligence. They carry 99% of global data traffic and are the supporting technology for my country's future innovative applications such as the Industrial Internet, enterprise cloud migration, edge computing, and digital transformation. With the rapid adoption of new technologies such as 5G, artificial intelligence (AI), the Internet of Things, and VR / AR, the explosive growth in data traffic is driving increasing bandwidth requirements. Ethernet speeds are advancing from 400GbE to 800GbE, and are expected to break the 1TbE technical barrier by 2025. This is driving the generational transition of data centers. Optical interconnects based on 850nm vertical-cavity surface-emitting lasers (VCSELs) have become the standard solution for short-distance data transmission within data centers, between racks, and between boards, due to their high transmission rates, low power consumption, and strong anti-interference capabilities.

[0003] VCSELs, with their advantages of high modulation speed, easy fiber coupling, and low power consumption, have become the preferred light source for short-distance optical interconnects. They are the most critical technology in determining the single-channel rate of optical modules. The core difficulty in increasing transmission rates lies in achieving a synergistic solution among the mutually constrained factors of reliability, high differential gain required for rate improvement, low carrier transport factor, precise matching of microcavity damping, and thermal effect management.

[0004] To form an ohmic contact with the electrode metal, heavily doped III-V materials are typically used as the electrical contact layer in the outermost layer of the device. However, due to the large refractive index step between the air and heavily doped III-V material interface, variations in the optical thickness of the outermost III-V material can cause phase mismatch, leading to changes in the photon lifetime and affecting the static and dynamic performance of the semiconductor laser. Summary of the Invention

[0005] The main purpose of the present invention is to provide a semiconductor laser, a light emitting component and an optical module, aiming to solve the above technical problems in the prior art.

[0006] Based on this, it is necessary to provide a semiconductor laser, a light emitting component and an optical module to address the above technical problems.

[0007] In a first aspect, the present application provides a semiconductor laser comprising

[0008] substrate;

[0009] a bottom reflector structure, disposed on the substrate;

[0010] an active layer disposed on the bottom reflector structure;

[0011] a top reflector structure disposed on the active layer, wherein the top reflector structure and the bottom reflector structure are used to define a resonant cavity; and

[0012] A photon lifetime control layer is provided on the top reflector structure, and the photon lifetime control layer is configured to control the photon lifetime of the resonant cavity.

[0013] In one embodiment, the photon lifetime control layer includes a photon lifetime control sublayer;

[0014] The photon lifetime regulating sublayer is arranged on the top reflector structure, or the photon lifetime regulating sublayer is a part of the top reflector structure; the thickness of the photon lifetime regulating sublayer is configured to obtain a lower photon lifetime.

[0015] In one embodiment, it further includes:

[0016] a refractive index compensation layer, wherein the refractive index compensation layer is disposed on the photon lifetime regulation sublayer, and the thickness of the refractive index compensation layer is configured to compensate for the refractive index change of the photon lifetime regulation sublayer caused by the thickness change.

[0017] In one embodiment, the photon lifetime regulating sublayer includes a III-V material, and the III-V material includes a GaAs material.

[0018] In one embodiment, the refractive index compensation layer is SiN.

[0019] In one embodiment, the thickness of the photon lifetime regulation sublayer is between 50 nm and 120 nm; the thickness of the refractive index compensation layer is between 130 nm and 400 nm.

[0020] In one embodiment, the thickness of the photon lifetime regulating sublayer is 80 nm, and the thickness of the refractive index compensation layer is 150 nm; or

[0021] The thickness of the photon lifetime regulating sublayer is 80 nm, and the thickness of the refractive index compensation layer is 380 nm.

[0022] In one embodiment, it further includes:

[0023] An optoelectronic confinement layer, formed in the top reflector structure, is configured to limit a light-emitting aperture of the semiconductor laser.

[0024] In one embodiment, the photovoltaic confinement layer includes any one of an air column type photovoltaic confinement layer, an oxidation confinement type photovoltaic confinement layer, an ion implantation type photovoltaic confinement layer, and a tunnel junction type photovoltaic confinement layer.

[0025] In one embodiment, the lasing wavelength of the semiconductor laser is 850±8 nm.

[0026] In a second aspect, the present application further provides a light emitting component, which includes a semiconductor laser as described in any one of the above items.

[0027] In a third aspect, the present application further provides an optical module, comprising an optical transmitting module and an optical receiving module, wherein the optical transmitting module adopts the aforementioned optical transmitting assembly.

[0028] The present invention has at least the following beneficial effects:

[0029] The semiconductor laser provided by the present invention achieves control over the photon lifetime of the resonant cavity of the semiconductor laser by placing a photon lifetime control layer on the top reflector structure. The photon lifetime affects the relaxation oscillation frequency of the device. A higher relaxation oscillation frequency requires a lower photon lifetime. The intrinsic modulation bandwidth of the laser increases with the increase of the relaxation oscillation frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the semiconductor laser structure in one embodiment of the present application;

[0031] Figure 2 Schematic diagram of the structure of a semiconductor laser in another embodiment of the present application;

[0032] Figure 3 Schematic diagram of the effect of different thicknesses of refractive index compensation layers on the top reflector and photon lifetime;

[0033] Figure 4 To simulate the effect of the refractive index compensation layer on the photon lifetime in photon lifetime control sublayers of different thicknesses.

[0034] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0036] It should be understood that the terms "first," "second," and the like used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are used solely to distinguish a first element from another element. For example, a first client may be referred to as a second client, and similarly, a second client may be referred to as a first client, without departing from the scope of this application.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, features specified as "first" or "second" may explicitly or implicitly include at least one of such features. "Multiple" means at least two, such as two, three, etc., unless otherwise specifically defined. "Several" means at least one, such as one, two, etc., unless otherwise specifically defined.

[0038] As described in the background of this application, data centers have become the fundamental carriers of new communication networks such as 5G and the Internet of Things, as well as the internet, cloud computing, and artificial intelligence. They carry 99% of global data traffic and are the supporting technology for my country's future innovative applications such as the Industrial Internet, enterprise cloud computing, and edge computing, as well as digital transformation. With the rapid adoption of new technologies such as 5G, artificial intelligence (AI), the Internet of Things, and VR / AR, the explosive growth in data traffic is placing increasing demands on bandwidth. Ethernet speeds are advancing from 400GbE to 800GbE, and are expected to break through the 1TbE technical barrier by 2025. This is driving the generational transition of data centers. Optical interconnects based on 850nm vertical-cavity surface-emitting lasers (VCSELs) have become the standard solution for short-distance data transmission within data centers, between racks, and between boards, due to their high transmission rates, low power consumption, and strong anti-interference capabilities.

[0039] VCSELs, with their advantages of high modulation speed, easy fiber coupling, and low power consumption, have become the preferred light source for short-distance optical interconnects. They are the most critical technology in determining the single-channel rate of optical modules. The core difficulty in increasing transmission rates lies in achieving a synergistic solution among the mutually constrained factors of reliability, high differential gain required for rate improvement, low carrier transport factor, precise matching of microcavity damping, and thermal effect management.

[0040] To form an ohmic contact with the electrode metal, heavily doped III-V materials are typically used as the electrical contact layer in the outermost layer of the device. However, due to the large refractive index step between the air and heavily doped III-V material interface, variations in the optical thickness of the outermost III-V material can cause phase mismatch, leading to changes in the photon lifetime and affecting the static and dynamic performance of the semiconductor laser.

[0041] The inventors of this application have discovered that the intrinsic modulation bandwidth of a laser increases with increasing relaxation oscillation frequency. The relaxation oscillation frequency is closely related to factors such as the differential gain of the resonant cavity, the photon volume within the cavity, and the photon lifetime. A higher relaxation oscillation frequency requires a higher differential gain, a smaller photon volume, and a shorter photon lifetime.

[0042] Based on this, it is necessary to provide a semiconductor laser, a light emitting component and an optical module to address the above technical problems.

[0043] Please refer to Figure 1-Figure 4 In the first aspect, the present application provides a semiconductor laser, comprising a substrate 10; a bottom reflector structure 110, disposed on the substrate 10; an active layer 120, disposed on the bottom reflector structure 110; a top reflector structure 130, disposed on the active layer 120, the top reflector structure 130 and the bottom reflector structure 110 being used to define a resonant cavity (refer to the active layer 120); and a photon lifetime control layer (not shown), disposed on the top reflector structure 130, the photon lifetime control layer being configured to control the photon lifetime of the resonant cavity.

[0044] In one embodiment, the photon lifetime control layer may include a photon lifetime control sublayer 140; the photon lifetime control sublayer 140 is disposed on the top reflector structure 130, or the photon lifetime control sublayer 140 is part of the top reflector structure 130; the thickness of the photon lifetime control sublayer 140 is configured to obtain a lower photon lifetime. Furthermore, the photon lifetime control sublayer includes a III-V material, and the III-V material includes GaAs.

[0045] In this specific embodiment, combined with Figure 4 It can be seen that when the photon lifetime control sublayer 140 is GaAs (in this case, the photon lifetime control sublayer 140 is part of the top reflector structure 130), as the thickness of the top GaAs layer decreases from phase matching to phase mismatch, the photon lifetime gradually decreases. It can be seen that the photon lifetime can be achieved by controlling the thickness of the top GaAs layer.

[0046] However, the inventors further discovered that as the phase mismatch of the top GaAs layer deepens, it will lead to destructive interference of the light field in the quantum well active region, causing a decrease in the optical confinement factor and differential gain. Therefore, in order to avoid this situation in the design, it is recommended to refer to Figure 2The present application further provides a refractive index compensation layer 150 on the photon lifetime regulation sublayer 140. The refractive index compensation layer 150 is provided on the photon lifetime regulation sublayer 140. The thickness of the refractive index compensation layer 150 is configured to compensate for the refractive index variation caused by the thickness variation of the photon lifetime regulation sublayer 140. In one embodiment, the refractive index compensation layer 150 is SiN.

[0047] In one embodiment, the thickness of the photon lifetime control sublayer 140 is between 50 nm and 120 nm; the thickness of the refractive index compensation layer 150 is between 130 nm and 400 nm.

[0048] In one embodiment, the thickness of the photon lifetime regulating sublayer 140 is 80 nm, and the thickness of the refractive index compensation layer 150 is 150 nm; or

[0049] The photon lifetime control sublayer 140 is 80 nm thick, and the refractive index compensation layer 150 is 380 nm thick. Using an 80 nm thick photon lifetime control sublayer 140 (GaAs) and a refractive index compensation layer 150 (SiN film) with a thickness of approximately 150 nm or 380 nm can achieve a lower photon lifetime, thereby increasing the relaxation oscillation frequency while reducing damping.

[0050] In this specific embodiment, the reflectivity and photon lifetime of the top reflector structure 130 covered with the refractive index compensation layer 150 can be calculated by using a transfer matrix method in combination with the following formula.

[0051]

[0052] in, is the photon lifetime, V g represents the group velocity including material dispersion and waveguide dispersion, L eff Represents the effective cavity length of the resonant cavity, L cav represents the length of the optical cavity, R top and R bot represent the reflectivity of the top reflector structure 130 and the bottom reflector structure 110 respectively.

[0053] Combine Figure 3 In the phase-matched top GaAs optical thickness structure shown in FIG, the SiN film thickness affects the reflectivity and photon lifetime of the top reflector structure 130. It can be seen that the photon lifetime exhibits periodic changes as the SiN film thickness changes.

[0054] In one embodiment, the present invention further includes: a photoelectric confinement layer 132 formed in the top reflector structure 130 and configured to limit the light-emitting aperture of the semiconductor laser.

[0055] In one embodiment, the photovoltaic confinement layer 132 includes any one of an air column type photovoltaic confinement layer, an oxidation confinement type photovoltaic confinement layer, an ion implantation type photovoltaic confinement layer, and a tunnel junction type photovoltaic confinement layer.

[0056] In one embodiment, the lasing wavelength of the semiconductor laser is 850±8 nm. For example, the lasing wavelength of the semiconductor laser of the present application is 850 nm, or 852 nm, or 854 nm, or 857 nm. This application does not make further limitations on this.

[0057] In this specific embodiment, please refer to Figure 2 The bottom reflector structure 110 and the top reflector structure 130 define the resonant cavity structure of the vertical cavity surface emitting laser of the present application, that is, the area between the bottom reflector structure 110 and the top reflector structure 130 is the resonant cavity. The resonant cavity is used to generate standing waves. Standing waves are waves formed by two coherent waves propagating in opposite directions on the same straight line and superimposed on each other. Specifically, when the two waves are in phase, their amplitudes add together to form antinodes (i.e., crests). When the two waves are in opposite phases, their amplitudes subtract from each other to form nodes (i.e., troughs). Therefore, the positions of the crests and troughs of the standing wave are fixed.

[0058] In one embodiment, the bottom reflector structure 110 may include a periodically stacked DBR structure, that is, it includes multiple reflectors with an optical thickness of one-quarter the laser wavelength, and the multiple reflectors are arranged alternately according to high and low refractive indices. The top reflector structure 130 also includes a periodically stacked DBR structure, that is, it includes multiple reflectors with an optical thickness of one-quarter the laser wavelength, and the multiple reflectors are arranged alternately according to high and low refractive indices. It can be understood that the components, number of stacking periods, etc. of the DBR structure of the bottom reflector structure 110 and the DBR structure of the top reflector structure 130 may be the same or different, and this embodiment does not limit this. Among them, the material of the top reflector structure 130 and the bottom reflector structure 110 can be a dielectric material with electrical insulation, for example, it can include silicon nitride, silicon oxide, aluminum oxide or titanium oxide. The material of the top reflector structure 130 and the bottom reflector structure 110 can also be a semiconductor material, for example, it can include GaAs and AlGaAs.

[0059] The material of the substrate 10 includes but is not limited to GaAs, InP, Si, etc. The bottom reflector structure 110 and the top reflector structure 130 may include a film layer with a periodic change in refractive index to achieve efficient reflection or transmission of light within a specific wavelength range. The film layer with a periodic change in refractive index can be composed of semiconductor materials, dielectric materials, metal-dielectric hybrid materials, etc. For example, the bottom reflector structure 110 can be an N-type semiconductor layer, and the top reflector structure 130 can be a P-type semiconductor layer. For another example, the bottom reflector structure 110 can be a P-type semiconductor layer, and the top reflector structure 130 can be an N-type semiconductor layer. Optionally, the material of the N-type semiconductor layer and the P-type semiconductor layer can be but is not limited to GaAs, AlGaAs, etc., which is not limited here. As long as the definition of the resonant cavity can be achieved, it falls within the protection scope of this embodiment. Specifically, the resonant cavity structure can also include a photoelectric confinement layer 132, and the photoelectric confinement layer 132 is formed in the top reflector structure 130.

[0060] The active layer 120 may include one active region, two active regions, three active regions, or four active regions. Each active region may include one or more multi-quantum well structures. The multi-quantum well structure is used to generate stimulated emission photons. The emitted photons are continuously reflected in the resonant cavity defined by the bottom reflector structure 110 and the top reflector structure 130, and are continuously enhanced during the reflection process, ultimately emitting laser light at a specific wavelength and with sufficient energy.

[0061] The multi-quantum well structure is where laser gain amplification is generated, and the center position of the multi-quantum well structure can be aligned with the position where the light field is strongest to achieve a greater amplification effect. Furthermore, in the case of multiple multi-quantum well structures, the confinement factors of the multi-quantum well structures in the same section of the light field are within the same preset range, that is, the confinement factors of each multi-quantum well structure are maintained at the same level, so that the contribution of each multi-quantum well structure to luminescence is similar. It can be understood that similar luminescence contributions mean that the injection of current into each multi-quantum well structure is more uniform, which helps to reduce the threshold current of the device, thereby reducing the power consumption of the device and extending its service life. Moreover, when the contribution of each multi-quantum well structure to luminescence is similar, the distribution of carriers in each multi-quantum well structure will be more uniform, which helps to reduce the recombination loss of carriers, thereby improving the overall luminescence efficiency of the device.

[0062] Typically, the number of photoelectric confinement layers 132 is not greater than the number of active layers 120, for example, there may be 2, 3, 4, etc. The photoelectric confinement layer 132 is used to limit the light-emitting area of ​​the vertical cavity surface emitting laser. Specifically, the photoelectric confinement layer 132 is located on the side of the corresponding active layer 120 away from the substrate 10 to limit the flow of current so that the current flows only within the light-emitting area defined by the photoelectric confinement layer 132, thereby reducing unnecessary energy consumption, and further reducing the threshold current and increasing the current density. Moreover, the photoelectric confinement layer 132 can also confine the light field within the light-emitting area defined by the photoelectric confinement layer 132, reducing the scattering and diffraction of light, thereby optimizing the divergence angle of the device and improving the beam quality. Typically, the photoelectric confinement layer 132 is set at the position where the light field intensity is lowest, that is, at the trough of the standing wave, so that it has a smaller confinement factor, which helps to reduce the divergence angle of the device.

[0063] The photoelectric confinement layer 132 can include any of an air column type photoelectric confinement layer, an oxidation confinement type photoelectric confinement layer, an ion implantation type photoelectric confinement layer, and a tunnel junction type photoelectric confinement layer. The air column type photoelectric confinement layer confines current and light through air columns. The air columns are hollow structures formed using dry etching techniques, and their refractive index is lower than that of the surrounding semiconductor material, thereby effectively confining light to the central region. The ion implantation type photoelectric confinement layer modifies the electrical properties of the semiconductor material by injecting ions into it, forming a high-resistance region. The high-resistance region can restrict the flow of current, thereby indirectly limiting the light generation area.

[0064] In one embodiment, the oxidation-restricted photoelectric confinement layer includes an unoxidized region of AlGaAs material with a high Al content and an oxidized region of aluminum oxide material. The oxidized region is arranged outside the unoxidized region, and the unoxidized region forms a light-emitting region for effective current injection. Among them, the semiconductor layer in the unoxidized region of the photoelectric confinement layer 132 can be understood as an opening, and the opening is used to define the light-emitting region of the vertical cavity surface emitting laser. When current enters, the current can only flow to the active layer 120 through the opening in the photoelectric confinement layer 132, thereby achieving the limitation of the current injection path and the optical mode field. Furthermore, the AlGaAs layer with a high aluminum content can be converted into aluminum oxide through a selective oxidation process to form an outer unoxidized region.

[0065] In one embodiment, the tunnel junction type photoelectric confinement layer includes at least one highly doped N-type structure layer and at least one highly doped P-type structure layer. Specifically, a potential barrier is formed between the highly doped N-type structure layer and the highly doped P-type structure layer, and electrons are allowed to pass through the potential barrier by tunneling, thereby achieving lateral confinement of the current. In one embodiment, the material of the N-type structure layer and the P-type structure layer is Al X Ga 1-X As, the doping concentration of the N-type structure layer and the P-type structure layer is greater than 1e18 cm -3 , where 0≤x≤1.

[0066] Secondly, this application also provides an optical transmitter assembly comprising a semiconductor laser as described in any of the preceding items. The optical transmitter assembly in this specific embodiment may be a Transmitting Optical Sub-Assembley (TOSA), which primarily converts electrical signals into optical signals. The optical transmitter assembly comprises a light source (a semiconductor light-emitting diode or laser diode) as the core, and an LD chip, a monitoring photodiode (MD), and other components are packaged in a compact structure (a TO coaxial package or a butterfly package).

[0067] Thirdly, the present application also provides an optical module comprising an optical transmitter module and an optical receiver module, wherein the optical transmitter module utilizes the aforementioned optical transmitter assembly. The optical receiver module in this specific embodiment, also known as a Resceiving Optical Sub-Assembley (ROSA), is typically constructed by assembling a PIN or ADP photodiode and a TIA in a sealed metal housing in a high-data-rate optical fiber module.

[0068] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The above-described embodiments merely represent several implementation methods of the embodiments of the present application. The descriptions thereof are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the concept of the embodiments of the present application, and these all fall within the scope of protection of the embodiments of the present application. Therefore, the scope of protection of the patent of the embodiments of the present application shall be based on the appended claims.

Claims

1. A semiconductor laser, characterized in that include substrate; a bottom reflector structure, disposed on the substrate; an active layer disposed on the bottom reflector structure; a top reflector structure disposed on the active layer, wherein the top reflector structure and the bottom reflector structure define a resonant cavity; as well as a photon lifetime control layer, provided on the top reflector structure, wherein the photon lifetime control layer is configured to control the photon lifetime of the resonant cavity; The photon lifetime regulation layer includes a photon lifetime regulation sublayer, which is part of the top reflector structure; the thickness of the photon lifetime regulation sublayer is configured to obtain a lower photon lifetime; a refractive index compensation layer, the refractive index compensation layer being disposed on the photon lifetime regulation sublayer, the thickness of the refractive index compensation layer being configured to compensate for a refractive index change caused by a thickness change of the photon lifetime regulation sublayer; The thickness of the photon lifetime regulating sublayer is between 50nm and 120nm; the thickness of the refractive index compensation layer is between 130nm and 400nm.

2. The semiconductor laser according to claim 1, wherein The photon lifetime regulating sublayer includes a III-V group material, and the III-V group material includes a GaAs material.

3. The semiconductor laser according to claim 2, wherein The refractive index compensation layer is SiN.

4. The semiconductor laser according to claim 3, wherein The thickness of the photon lifetime regulating sublayer is 80 nm, and the thickness of the refractive index compensation layer is 150 nm; or The thickness of the photon lifetime regulating sublayer is 80 nm, and the thickness of the refractive index compensation layer is 380 nm.

5. The semiconductor laser according to any one of claims 1 to 4, characterized in that: Also includes: An optoelectronic confinement layer, formed in the top reflector structure, is configured to limit a light-emitting aperture of the semiconductor laser.

6. The semiconductor laser according to claim 5, characterized in that The photoelectric confinement layer includes any one of an air column type photoelectric confinement layer, an oxidation confinement type photoelectric confinement layer, an ion implantation type photoelectric confinement layer and a tunnel junction type photoelectric confinement layer.

7. The semiconductor laser according to any one of claims 1 to 4, characterized in that: The lasing wavelength of the semiconductor laser is 850±8nm.

8. A light emitting component, characterized in that: The light emitting component includes the semiconductor laser according to any one of claims 1 to 7.

9. An optical module, characterized in that: It comprises a light emitting module and a light receiving module, and the light emitting module adopts the light emitting assembly according to claim 8.

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