Semiconductor laser, optical transmitting assembly and optical module

Abstract

Embodiments of the present application relate to a semiconductor laser, a light emitting assembly and an optical module. The semiconductor laser comprises a resonant cavity structure, the resonant cavity structure comprises a resonant cavity, the resonant cavity is used for generating a standing wave, the resonant cavity is defined by a bottom mirror structure and a top mirror structure; a multi-quantum well structure is arranged in the resonant cavity, the multi-quantum well structure is arranged at a wave peak position of the resonant cavity; the thickness of the resonant cavity is designed to be less than two-thirds of a lasing wavelength to improve the relaxation oscillation frequency of the semiconductor laser. The application of the scheme can improve the relaxation oscillation frequency and improve the device modulation bandwidth.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of semiconductor lasers, and particularly to a surface emitting laser. BACKGROUND

[0002] Currently, data centers have become the basic carrier of new communication networks such as 5G and Internet of Things, and fields such as the Internet, cloud computing and artificial intelligence, carrying 99% of global data traffic, and are the supporting technologies for China to realize innovative applications such as industrial Internet, enterprise cloud, edge computing and digital transformation in the future. With the rapid popularization and application of new technologies such as 5G, artificial intelligence (AI), Internet of Things, VR / AR, the explosive growth of data traffic continues to increase the demand for bandwidth, and the speed of Ethernet is advancing from 400 GbE to 800 GbE. It is expected to break through the 1 TbE technical barrier by 2025, driving the intergenerational replacement of data centers. Optical interconnection with 850 nm semiconductor lasers (VCSEL) as the carrier has become the standard solution for short-distance data transmission between internal machine rooms, racks and boards in data centers due to its high transmission rate, low power consumption and strong anti-interference capability.

[0003] VCSEL has the advantages of high modulation speed, easy coupling with optical fiber, low power consumption, etc. It has become the preferred light source for short-distance optical interconnection and is the most critical technology for determining the single-channel rate of optical modules. The core difficulty of its transmission rate improvement lies in how to obtain a synergistic effect from the mutually influencing factors of high differential gain required for reliability and rate improvement, low carrier transport factor, precise matching of microcavity damping and thermal effect management. SUMMARY

[0004] Therefore, it is necessary to provide a semiconductor laser, an optical transmitting assembly and an optical module to solve the above technical problems.

[0005] In a first aspect, the present application provides a semiconductor laser, comprising a resonant cavity structure, wherein the resonant cavity structure comprises a resonant cavity for generating a standing wave, and the resonant cavity is defined by a bottom mirror structure and a top mirror structure.

[0006] A multi-quantum well structure is arranged in the resonant cavity, and the multi-quantum well structure is arranged at a wave peak position of the resonant cavity. The thickness of the resonant cavity is designed to be less than two-thirds of a lasing wavelength to improve the relaxation oscillation frequency of the semiconductor laser.

[0007] In one embodiment, the thickness of the resonant cavity is between one lasing wavelength and two-thirds of a lasing wavelength; or

[0008] The thickness of the resonant cavity is between two-thirds of a lasing wavelength and one lasing wavelength; or

[0009] The thickness of the resonant cavity is less than or equal to one-half of the lasing wavelength.

[0010] In one embodiment, the multi-quantum well structure includes a plurality of well layers and barrier layers arranged in an interlaced manner, and the strain mode and / or the strain amount of the well layers and the barrier layers are not completely identical.

[0011] In one embodiment, the strain mode of at least some adjacent well layers and barrier layers is different; or

[0012] The strain mode of at least some adjacent well layers and barrier layers is identical.

[0013] In one embodiment, the strain amount of at least some adjacent well layers and barrier layers is different; or

[0014] The strain amount of at least some adjacent well layers and barrier layers is identical.

[0015] In one embodiment, the strain amount of at least some well layers changes in a stepwise manner along a direction close to the top mirror structure; or

[0016] The strain amount of at least some barrier layers changes in a stepwise manner.

[0017] In one embodiment, the strain amount of at least some well layers changes in an arithmetic sequence manner along a direction close to the top mirror structure; or

[0018] The strain amount of at least some barrier layers changes in an arithmetic sequence manner.

[0019] In one embodiment, the strain amount of at least some well layers changes in a geometric sequence manner along a direction close to the top mirror structure; or

[0020] The strain amount of at least some barrier layers changes in a geometric sequence manner.

[0021] In one embodiment, the strain mode of at least some well layers is identical along a direction close to the top mirror structure; or

[0022] The strain mode of at least some barrier layers is identical.

[0023] In one embodiment, the strain mode includes any one of compressive strain, tensile strain, and no strain.

[0024] In one embodiment, the strain amount is between 0.03% and 12%.

[0025] In one embodiment, the multi-quantum well structure includes a plurality of well layers and barrier layers arranged in an interlaced manner, at least one of the well layers is a compressive strain well layer, and the content of indium component in the compressive strain well layer is 0.12.

[0026] In one embodiment, the well layer and the barrier layer are InGaAs and AlGaAs materials, respectively.

[0027] In one embodiment, it further includes:

[0028] An oxide confinement layer is formed in the top reflector structure, the oxide confinement layer is disposed adjacent to the resonant cavity, and the oxide confinement layer is used to define the light-emitting region of the semiconductor laser.

[0029] This application provides a semiconductor laser comprising a resonant cavity structure, wherein the resonant cavity structure includes a resonant cavity for generating standing waves, the resonant cavity being defined by a bottom mirror structure and a top mirror structure; a multi-quantum well structure is disposed within the resonant cavity, the multi-quantum well being located at the wave crest position of the resonant cavity; the thickness of the resonant cavity is designed to be less than half a lasing wavelength, that is, this application employs a method of reducing photon volume in epitaxial design (designing the resonant cavity length to be less than half a lasing wavelength) and placing the multi-quantum well structure at the wave crest position within the microcavity to obtain a larger optical confinement factor, thereby increasing the relaxation oscillation frequency.

[0030] Secondly, this application provides a light emitting component, which includes the aforementioned semiconductor laser.

[0031] Thirdly, this application provides an optical module, including an optical emitting module and an optical receiving module, wherein the optical emitting module adopts the aforementioned optical emitting component. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a semiconductor laser in one embodiment of this application;

[0033] Figures 2a-2e for Figure 1 Schematic diagram of different trap-barrier layer arrangements in the embodiments;

[0034] Figure 3 This is a schematic diagram of the optical field intensity distribution inside the resonant cavity in one embodiment of this application;

[0035] Figure 4 This is a schematic diagram of the structure of a semiconductor laser according to another embodiment of this application.

[0036] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0037] In order to make the purposes, technical solutions and advantages of the present application clearer, further detailed description will be made to the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0038] It can be understood that the terms "first", "second", etc. used in the present application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first client can be called the second client, and similarly, the second client can be called the first client.

[0039] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. The meaning of "multiple" is at least two, such as two, three, etc., unless otherwise explicitly and specifically limited. The meaning of "several" is at least one, such as one, two, etc., unless otherwise explicitly and specifically limited.

[0040] As described in the background of the present application, at present, data centers have become the basic carrier of new communication networks such as 5G, Internet of Things, and fields such as Internet, cloud computing and artificial intelligence, carrying 99% of global data traffic, and are the supporting technologies for realizing innovative applications such as industrial Internet, enterprise cloud, edge computing, and digital transformation in China in the future. With the rapid popularization and application of new technologies such as 5G, artificial intelligence (AI), Internet of Things, VR / AR, the increasing demand for bandwidth of explosive growth of data traffic, the speed of Ethernet is advancing from 400GbE to 800GbE, and it is expected to break through the 1TbE technical barrier by 2025, driving the intergenerational replacement of data centers. The optical interconnection with 850nm semiconductor laser (VCSEL) as the carrier has become the standard solution for short-distance data transmission in the internal machine room, inter-rack, and inter-board of data centers due to its high transmission rate, low power consumption, and strong anti-interference capability.

[0041] VCSEL (Vertical-Cavity Surface-Emitting Laser, semiconductor laser) has the advantages of high modulation speed, easy coupling with optical fiber, low power consumption, etc. It has become the preferred light source for short-distance optical interconnection, and is the most critical technology to determine the single-channel rate of optical modules. The core difficulty of transmission rate improvement lies in how to obtain a synergistic effect from the mutually influencing factors of high differential gain required by reliability and rate improvement, low carrier transport factor, precise matching of microcavity damping and thermal effect management, etc.

[0042] Based on this, refer to Figures 1-4 The present application provides a semiconductor laser, which may be, for example, a semiconductor laser VCSEL or an edge emitting laser EEL, and the present application takes the semiconductor laser VCSEL as an example for illustration. The semiconductor laser can include a resonant cavity structure (not shown in the figure), which includes a resonant cavity for generating a standing wave, and the resonant cavity is defined by a bottom mirror structure 110 and a top mirror structure 130. Specifically, the bottom mirror structure 110 and the top mirror structure 130 define the resonant cavity structure of the semiconductor laser of the present application, that is, the area between the bottom mirror structure 110 and the top mirror structure 130 is the resonant cavity. The resonant cavity is used to generate a standing wave, which is a wave formed by two coherent waves propagating in opposite directions on the same straight line and superimposing each other. Specifically, when the phases of the two waves are the same, their amplitudes are added to form a wave crest (i.e., a wave peak). When the phases of the two waves are opposite, their amplitudes are subtracted to form a wave node (i.e., a wave trough). Therefore, the positions of the wave peaks and wave troughs of the standing wave are fixed.

[0043] The resonant cavity is provided with a multi-quantum well structure 120, which is arranged at the wave peak position of the resonant cavity. Specifically, the multi-quantum well structure 120 is used to generate photons of stimulated radiation, and the emitted photons are continuously reflected in the resonant cavity defined by the bottom mirror structure 110 and the top mirror structure 130, and continuously enhanced in the process of reflection, so as to finally emit laser with a specific wavelength and sufficient energy.

[0044] The multi-quantum well structure 120 is the place where laser gain amplification is generated, and the central position of the multi-quantum well structure 120 can be aligned with the position of the strongest light field (i.e., the wave peak position of the resonant cavity), so as to play a greater amplification effect. Further, the number of multi-quantum well structures 120 can be multiple, and in the case of including multiple multi-quantum well structures 120, the confinement factor of the multi-quantum well structures 120 in the same segment of light field is within the same predetermined range, that is, the confinement factors of each multi-quantum well structure 120 are maintained at the same level, so that the contribution of each multi-quantum well structure 120 to light emission is similar. It can be understood that similar light emission contribution means that the injection of current in each multi-quantum well structure 120 is more uniform, which helps to reduce the threshold current of the device, thereby reducing the power consumption of the device and prolonging its service life. Moreover, when the contribution of each multi-quantum well structure 120 to light emission is similar, the distribution of carriers in each multi-quantum well structure 120 will be more uniform, which helps to reduce the recombination loss of carriers, thereby improving the overall light emission efficiency of the device.

[0045] The inventors of the present application found through research that the intrinsic modulation bandwidth of a laser is improved with the increase of the relaxation oscillation frequency, which is closely related to the differential gain of the quantum well, the intracavity photon volume and other factors. A larger relaxation oscillation frequency requires a high differential gain and a small photon volume. For reference Figure 3 The thickness of a conventional resonant cavity is generally designed to be two-thirds of the lasing wavelength, but the photon volume at this thickness is still large and the effect of improving the intrinsic modulation bandwidth is not significant enough. Therefore, the present application first reduces the photon volume to improve the relaxation oscillation frequency of a semiconductor laser, and then improves the intrinsic modulation bandwidth of the semiconductor laser. Specifically, the thickness of the resonant cavity is designed to be less than two-thirds of the lasing wavelength. Further, the thickness of the resonant cavity is designed to be between one lasing wavelength and two-thirds of the lasing wavelength, excluding two-thirds of the lasing wavelength; for example, the thickness of the resonant cavity is designed to be one lasing wavelength, i.e. λ, or the thickness of the resonant cavity is designed to be four-thirds of the lasing wavelength, i.e. 4 / 3λ; or, the thickness of the resonant cavity is between one-half of the lasing wavelength and one lasing wavelength, excluding one lasing wavelength; for example, the thickness of the resonant cavity is designed to be greater than one-half of the lasing wavelength, i.e. 1 / 2λ (excluding one-half of the lasing wavelength), or the thickness of the resonant cavity is designed to be three-fifths of the lasing wavelength, i.e. 3 / 5λ, or the thickness of the resonant cavity is designed to be seven-tenths of the lasing wavelength, i.e. 7 / 10λ, or the thickness of the resonant cavity is designed to be four-fifths of the lasing wavelength, i.e. 4 / 5λ; or, the thickness of the resonant cavity is between less than or equal to one-half of the lasing wavelength, for example, the thickness of the resonant cavity is equal to one-half of the lasing wavelength, i.e. 1 / 2λ, or the thickness of the resonant cavity is equal to two-fifths of the lasing wavelength, i.e. 2 / 5λ, and so on. The present application does not make further elaboration, Figure 3 For the case of setting the thickness of the resonant cavity to one-half of the lasing wavelength, i.e. 1 / 2λ, in theory, a smaller photon volume is more beneficial to the improvement of the relaxation oscillation frequency.

[0046] Further, the bottom mirror structure 110 can include a periodic stack DBR structure, i.e. a plurality of mirrors with a quarter of the lasing wavelength optical thickness, and the plurality of mirrors are arranged alternately with high and low refractive index. The top mirror structure 130 also includes a periodic stack DBR structure, i.e. a plurality of mirrors with a quarter of the lasing wavelength optical thickness, and the plurality of mirrors are arranged alternately with high and low refractive index. It can be understood that the DBR structure of the bottom mirror structure 110 and the DBR structure of the top mirror structure 130 can be the same or different in composition, stack period number, etc., which is not limited in the embodiment. The material of the top mirror structure 130 and the bottom mirror structure 110 can be a dielectric material with electrical insulation, for example, can include silicon nitride, silicon oxide, aluminum oxide or titanium oxide, etc. The material of the top mirror structure 130 and the bottom mirror structure 110 can also be a semiconductor material, for example, can include GaAs and AlGaAs.

[0047] In one embodiment, the semiconductor laser described above can further include a substrate 10 (10) Figure 4 ), the bottom mirror structure 110 is epitaxially grown on the substrate 10, and the material of the substrate 10 includes but is not limited to GaAs, InP, Si, etc. The bottom mirror structure 110 and the top mirror structure 130 can include a refractive index periodically varying film layer to achieve high efficiency reflection or transmission of light in a specific wavelength range. The refractive index periodically varying film layer can be composed of semiconductor materials, dielectric materials, metal-dielectric hybrid materials, etc. For example, the bottom mirror structure 110 can be an N-type semiconductor layer, and the top mirror structure 130 can be a P-type semiconductor layer. For another example, the bottom mirror structure 110 can be a P-type semiconductor layer, and the top mirror structure 130 can be an N-type semiconductor layer. Alternatively, the material of the N-type semiconductor layer and the P-type semiconductor layer can be but not limited to GaAs, AlGaAs, etc., which is not limited herein, as long as it can achieve the limitation of the resonant cavity, it belongs to the protection scope of the embodiment. Specifically, the resonant cavity structure can further include an oxide confinement layer 132 formed in the top mirror structure 130.

[0048] In one embodiment, the semiconductor laser as described above can further comprise an oxide confinement layer 132 formed in the top mirror structure 130, the oxide confinement layer 132 is disposed adjacent to the resonant cavity, and the oxide confinement layer 132 is configured to define the light emitting region of the semiconductor laser. Specifically, the oxide confinement layer 132 is disposed on the side of the corresponding multiple quantum well structure 120 away from the substrate 10, so as to confine the current flow to the light emitting region defined by the oxide confinement layer 132, thereby reducing the unnecessary energy consumption, and further reducing the threshold current and increasing the current density. Moreover, the oxide confinement layer 132 can also confine the optical field to the light emitting region defined by the oxide confinement layer 132, thereby reducing the scattering and diffraction of the light, and further optimizing the divergence angle of the device and improving the beam quality. Generally, the oxide confinement layer 132 is disposed at the position with the lowest light field intensity, i.e. the valley of the standing wave, so as to have a smaller confinement factor, thereby helping to reduce the divergence angle of the device.

[0049] The oxide confinement layer 132 can comprise any one of an air post type electro-optic confinement layer, an oxide confinement type electro-optic confinement layer, an ion implantation type electro-optic confinement layer, and a tunnel junction type electro-optic confinement layer. The air post type electro-optic confinement layer confines the current and the light by means of an air post, which is a hollow structure formed by dry etching technology and has a lower refractive index than the surrounding semiconductor material, thereby effectively confining the light in the central region. The ion implantation type electro-optic confinement layer changes the electrical properties of the semiconductor material by implanting ions into the semiconductor material, thereby forming a high resistance region that can confine the current flow, and thereby indirectly confine the light generating region.

[0050] In one embodiment, the oxide confinement type electro-optic confinement layer comprises an unoxidized region of AlGaAs material with a high Al component and an oxidized region of aluminum oxide material, the oxidized region is disposed outside the unoxidized region, and the unoxidized region forms the light emitting region of the effective current injection. The semiconductor layer of the unoxidized region in the oxide confinement layer 132 can be understood as an opening, which defines the light emitting region of the semiconductor laser. When the current enters, the current can only flow to the multiple quantum well structure 120 through the opening in the oxide confinement layer 132, thereby realizing the confinement of the current injection path and the optical mode field. Further, the high Al component AlGaAs layer can be converted into aluminum oxide by selective oxidation process to form the peripheral unoxidized region.

[0051] In one embodiment, the tunnel junction type electro-optic confinement layer comprises at least one high-doped N-type structure layer and at least one high-doped P-type structure layer. Specifically, the high-doped N-type structure layer and the high-doped P-type structure layer form a potential barrier therebetween, and allow electrons to pass through the potential barrier by tunneling effect, thereby realizing the lateral confinement of the current. In one embodiment, the materials of the N-type structure layer and the P-type structure layer are selected as Alx Ga 1-x As, the doping concentration of the N-type structure layer and the P-type structure layer is greater than 1e 18 cm -3 , wherein 0≤x≤1.

[0052] In one embodiment, since the hole mobility in GaAs is much higher than that in AlGaAs, the semiconductor laser of the present application can further comprise a heavily doped GaAs layer placed on the top mirror structure 130 as a P-type electrical contact layer.

[0053] In one embodiment, the semiconductor laser of the present application can further comprise a heavily doped GaAs layer placed on the top mirror structure 130 as a P-type electrical contact layer. Figure 1 The multi-quantum well structure 120 of the present application can comprise a plurality of well layers and barrier layers arranged in an overlapping manner, and the strain mode and / or strain amount of the well layers and the barrier layers are not completely the same. For example, the strain mode can be any one of compressive strain, tensile strain or no strain, and the strain amount can be between 0.03% and 12%. It can be understood that the strain amount herein mainly refers to the tensile strain amount and the compressive strain amount, for example, when the well layer is compressively strained, the compressive strain amount of the well layer can be selected to be between 0.03% and 12%; or, when the well layer is tensilely strained, the tensile strain amount of the well layer can be selected to be between 0.03% and 12%; or, when the barrier layer is compressively strained, the compressive strain amount of the barrier layer can be selected to be between 0.03% and 12%; or, when the barrier layer is tensilely strained, the tensile strain amount of the barrier layer can be selected to be between 0.03% and 12%. Further, the strain amount can be selected to be between 0.03% and 0.05%; or, the strain amount can be selected to be between 0.05% and 1%; or, the strain amount can be selected to be between 1% and 1.5%; or, the strain amount can be selected to be between 1.5% and 2%; or, the strain amount can be selected to be between 2% and 2.5%; or, the strain amount can be selected to be between 2.5% and 3%; or, the strain amount can be selected to be between 3.5% and 4%; or, the strain amount can be selected to be between 4.5% and 5%; or, the strain amount can be selected to be between 5.5% and 6%; or, the strain amount can be selected to be between 6.5% and 7%; or, the strain amount can be selected to be between 7.5% and 8%; or, the strain amount can be selected to be between 8.5% and 9%; or, the strain amount can be selected to be between 9.5% and 10%; or, the strain amount can be selected to be between 10.5% and 11%; or, the strain amount can be selected to be between 11.5% and 12%. The above are only examples and should not be understood as a limitation of the present application.

[0054] In one embodiment, the strain mode of at least some adjacent well layers and barrier layers is different (for example, Figure 2a ,Figure 2b , Figure 2c , Figure 2d and Figure 2e ), for example, some adjacent well layers and barrier layers are compressively strained well layers and tensile strained barrier layers, or vice versa; or at least some adjacent well layers and barrier layers are of the same strain type (e.g. Figure 2a , Figure 2b , Figure 2d ), for example, some adjacent well layers and barrier layers are compressively strained well layers and barrier layers, or some adjacent well layers and barrier layers are tensile strained well layers and barrier layers. By setting the strain type of at least some adjacent well layers and barrier layers to be the same or different, compared with all being of one strain type, for example, all being tensile strained well layers and tensile strained barrier layers, such a stacking manner will cause strain accumulation, and if the number of stacked tensile strained well layers and tensile strained barrier layers is too large, the tensile strain of the multi-quantum well structure 120 will be too large, which will cause dislocations in the material of the multi-quantum well structure 120, affecting the performance of the semiconductor laser, and even causing the semiconductor optoelectronic device to malfunction. In addition, by setting the strain type of at least some adjacent well layers and barrier layers to be the same or different, effective stress compensation and release between tensile strain and compressive strain can be achieved, while introducing a certain amount of compressive strain to improve the relaxation oscillation frequency of the device, avoiding the generation of defects due to stress accumulation, and improving the reliability of the semiconductor laser.

[0055] In one embodiment, the strain of at least some adjacent well layers and barrier layers is different; or the strain of at least some adjacent well layers and barrier layers is the same. For example, when some adjacent well layers and barrier layers are of the same strain type, for example, both are compressively strained, the strain of adjacent compressively strained well layers and compressively strained barrier layers can be different, for example, the compressive strain of one compressively strained well layer is 2%, and the compressive strain of the compressively strained barrier layer adjacent to the compressively strained well layer is 1%.

[0056] For another example, when some adjacent well layers and barrier layers are of the same tensile strain type, the tensile strain of one tensile strained well layer is 2%, and the tensile strain of the tensile strained barrier layer adjacent to the tensile strained well layer is 1%. The larger strain of the tensile strained well layer causes changes in the crystal band properties of the well layer, causing the valence band side of the tensile strained well layer to rise more in the light hole band, so that the carrier transition mainly occurs between the conduction band and the light hole band. The effective mass of the hole in the light hole band in the direction perpendicular to the well is small, and the longitudinal migration speed of the light hole is fast, which is beneficial to the transport of holes and the effective transition of carriers, and at the same time, the hole state density is small, and it is easier to form population inversion under the same carrier injection, thereby improving the differential gain of the active layer. The improvement of the differential gain of the active layer is beneficial to the improvement of the rate performance of the semiconductor optoelectronic device.

[0057] For example, when the strain of the adjacent well layer and barrier layer is different, for example, the well layer is compressively strained and the barrier layer is tensile strained, the strain of the adjacent compressively strained well layer and tensile strained barrier layer can be different, for example, the compressive strain of one of the compressively strained well layers is 2%, and the compressive strain separates the light hole and heavy hole energy bands, resulting in a significant reduction in the mass of the heavy hole parallel to the interface, thereby causing a reduction in the hole state density and a significant increase in the quantum well differential gain; and the compressive strain of the tensile strained barrier layer adjacent to the compressively strained well layer is 3%, and by making the strain of the tensile strained barrier layer appropriately greater than the strain of the compressively strained well layer, the valence band side well region can be shallower, thereby controlling the number of bound states in the valence band side well layer. In addition, the tensile strained barrier layer is beneficial to the capture of valence band holes in the barrier layer and can shorten the transit time of the valence band holes in the barrier layer, which is beneficial to the transport of holes between the barrier layer and the well layer and improves the alternating current (AC) characteristics of the semiconductor laser; further, when at least one of the well layers is a compressively strained well layer, the content of indium in the compressively strained well layer can be 0.12. In this embodiment, the well layer and the barrier layer can be InGaAs and AlGaAs materials, respectively. The compressively strained InGaAs / AlGaAs quantum well with a large In content is used as the active region, and the compressive strain separates the light hole and heavy hole energy bands, resulting in a significant reduction in the mass of the heavy hole parallel to the interface, thereby causing a reduction in the hole state density and a significant increase in the quantum well differential gain, to obtain a larger relaxation oscillation frequency.

[0058] For example, when the strain of the adjacent well layer and barrier layer is different, for example, the well layer is tensile strained and the barrier layer is compressively strained, the strain of the adjacent tensile strained well layer and compressively strained barrier layer can be different, for example, the tensile strain of one of the tensile strained well layers is 2%, and the tensile strain of the compressively strained barrier layer adjacent to the tensile strained well layer is 3%, or vice versa.

[0059] For example, based on the above-mentioned cases where the strain of the adjacent well layer and barrier layer is the same or different, the strain of the adjacent barrier layer and well layer can be the same, for example, both are 2% strain. The same strain can effectively compensate and release the stress of the multi-quantum well structure 120 and improve the gain of the multi-quantum well structure 120. The specific description of this mode can be understood with reference to the foregoing embodiments, and the present application will not be repeated here.

[0060] In one embodiment, the strain of at least part of the well layers changes in a stepwise manner along a direction close to the top mirror structure 130; or the strain of at least part of the barrier layers changes in a stepwise manner. In this embodiment, the strain of part of the well layers changes in a stepwise manner based on the same strain type, such as compressive strain or tensile strain; or different strain types, such as both compressive strain and tensile strain, in which the strain of the well layer closest to the top mirror structure 130 is the maximum or minimum, i.e. stepwise increasing or stepwise decreasing. Similarly, the strain of part of the barrier layers changes in a stepwise manner based on the same strain type, such as compressive strain or tensile strain; or different strain types, such as both compressive strain and tensile strain, in which the strain of the barrier layer closest to the top mirror structure 130 is the maximum or minimum, i.e. stepwise increasing or stepwise decreasing. The stepwise change of the strain can make the stress more evenly distributed, avoiding more defects.

[0061] In one embodiment, the strain of at least part of the well layers changes in an arithmetic sequence along a direction close to the top mirror structure 130; or the strain of at least part of the barrier layers changes in an arithmetic sequence. In this embodiment, the strain of part of the well layers changes in an arithmetic sequence based on the same strain type, such as compressive strain or tensile strain; or different strain types, such as both compressive strain and tensile strain, in which the strain of the well layer closest to the top mirror structure 130 is the maximum or minimum, i.e. arithmetic sequence increasing or arithmetic sequence decreasing. Similarly, the strain of part of the barrier layers changes in an arithmetic sequence based on the same strain type, such as compressive strain or tensile strain; or different strain types, such as both compressive strain and tensile strain, in which the strain of the barrier layer closest to the top mirror structure 130 is the maximum or minimum, i.e. arithmetic sequence increasing or arithmetic sequence decreasing. The arithmetic sequence change of the strain can make the stress more evenly distributed, avoiding more defects.

[0062] In one embodiment, the strain of at least part of the well layers changes in a geometric progression along the direction close to the top mirror structure; or the strain of at least part of the barrier layers changes in a geometric progression. In this embodiment, the strain of part of the well layers in a geometric progression can be based on the same strain of the well layers, such as all compressive strain or all tensile strain; or different strain of the well layers, such as both compressive strain and tensile strain, in which the strain of the well layer closest to the top mirror structure 130 is the largest or the smallest, i.e. in a geometric progression or in an arithmetic progression. Similarly, the strain of part of the barrier layers in a geometric progression can be based on the same strain of the barrier layers, such as all compressive strain or all tensile strain; or different strain of the barrier layers, such as both compressive strain and tensile strain, in which the strain of the barrier layer closest to the top mirror structure 130 is the largest or the smallest, i.e. in a geometric progression or in an arithmetic progression. The strain in a geometric progression can make the stress more evenly distributed and avoid more defects.

[0063] In one embodiment, the strain of at least part of the well layers is the same along the direction close to the top mirror structure; or the strain of at least part of the barrier layers is the same. The strain of at least part of the well layers is the same (such as Figure 2a , Figure 2b , Figure 2c , Figure 2d and Figure 2e ), such as all compressive strain or all tensile strain, or vice versa; or the strain of at least part of the barrier layers is the same, such as all compressive strain or all tensile strain, or vice versa. This embodiment does not require the strain of the well layers and the strain of the barrier layers to be the same. By setting the strain of at least part of the well layers to be the same or the strain of at least part of the barrier layers to be the same, compared with all the same strain, such as all tensile strain and all compressive strain, the strain accumulates, which can cause the material of the multi-quantum well structure 120 to be dislocated, affect the performance of the semiconductor laser, and even cause the semiconductor optoelectronic device to malfunction. In addition, by controlling the strain of part of the well layers and the strain of part of the barrier layers, the tensile strain and the compressive strain in the multi-quantum well structure 120 can be effectively compensated and released, which can improve the relaxation oscillation frequency of the device by introducing a certain amount of compressive strain, avoid the generation of defects due to stress accumulation, and improve the reliability of the semiconductor laser.

[0064] As Figure 4As shown, the semiconductor laser further includes a dielectric layer 140 formed on the top mirror structure 130; the dielectric layer 140 is a layer that at least partially insulates the top metal 150 from one or more other layers or features (e.g., sidewalls of a trench). Further, the dielectric layer 140 can be used to protect the top mirror structure 130. In some embodiments, the dielectric layer 140 can include, for example, silicon nitride (SiNX), silicon dioxide (Si02), a polymer dielectric, or another type of insulating material. In some embodiments, the thickness t of the dielectric layer 140 can be in a range from about 0.92 x (l / nd) to about 1.45 x (l / nd), where l is the wavelength of the vertical cavity surface emitting laser and nd is the refractive index of the dielectric material. More generally, the thickness T of the dielectric layer 140 can equal the thickness t plus or minus a value that corresponds to a multiple of the wavelength of the semiconductor laser divided by twice the refractive index of the dielectric material (e.g., T = t ± X x l / (2*nd), where 0.92 x (l / nd) < t < 1.45 x (l / nd), and X is an integer value such as 0, 1, 2, etc.). In some embodiments, the thickness T of the dielectric layer 140 can vary by some amount (e.g., ±10 nm, ±15 nm) depending on the VCSEL design. Thus, in some embodiments, the thickness of the dielectric layer 140 is within a value of about 15 nm that equals a value in a range from about 0.92 x (l / nd) to about 1.45 x (l / nd) plus or minus a value equal to X x l / (2*nd), where l is the wavelength of the VCSEL, nd is the refractive index of the dielectric material, and X is an integer value.

[0065] Figure 4 In some embodiments, the semiconductor laser can further include a top metal 150 that is a top metal layer at the front side of the semiconductor laser. In some embodiments, the top metal 150 can be a layer that is in direct contact with a heavily doped P-type electrical contact GaAs layer (e.g., through a via through the dielectric layer 140), or a layer that is in direct contact with an ohmic contact metal layer (not shown) disposed on the heavily doped P-type electrical contact GaAs layer. In some embodiments, the top metal 150 can be used as an anode for the semiconductor laser. In some embodiments, the top metal 150 can include a plated metal (e.g., gold (Au)) and / or a seed metal used in a plating process.

[0066] Figure 4In this embodiment, the semiconductor laser may further include a bottom metal 160, which is a bottom metal layer located on the rear side of the semiconductor laser. In some embodiments, the bottom metal 160 may be a layer that is electrically in contact with the entire surface of the substrate 10. In some embodiments, the top metal 150 may be used as a cathode for the semiconductor laser. In some embodiments, the top metal 150 may include an electroplated metal (e.g., gold (Au)) and / or a seed metal used in the electroplating process.

[0067] Figure 4 In this embodiment, the semiconductor laser may also include a proton injection region 170, which is a region that prevents free carriers from reaching the edge of the trench and / or isolates adjacent semiconductor lasers from each other (e.g., if the trench does not completely surround the semiconductor lasers). The proton injection region 170 may include, for example, an ion implantation material, such as a hydrogen / proton implantation material or a similar implantation element, to reduce conductivity.

[0068] Figure 4 The number, arrangement, thickness, order, and symmetry of the layers are provided as examples. In practice, with... Figure 4 Compared to the layers shown, a semiconductor laser may include additional layers, fewer layers, different layers, layers with different constructions, or layers with different arrangements. For example, in some embodiments, a semiconductor laser may include a semiconductor layer (e.g., one or more p-type layers) above a top mirror structure 130 (e.g., instead of dielectric layer 140). As another example, in some embodiments, a semiconductor laser may include an air interface (e.g., instead of dielectric layer 140 and top metal 150) above a top mirror structure 130. Additionally or alternatively, a set of layers (e.g., one or more layers) of a semiconductor laser may perform one or more functions described as being performed by another set of layers of a semiconductor laser, and any layer may include more than one layer.

[0069] In summary, this application provides a semiconductor laser comprising a resonant cavity structure, wherein the resonant cavity structure includes a resonant cavity for generating standing waves, the resonant cavity being defined by a bottom mirror structure and a top mirror structure; a multi-quantum well structure is disposed within the resonant cavity, the multi-quantum well being located at the wave crest position of the resonant cavity; the thickness of the resonant cavity is designed to be less than half a lasing wavelength, that is, this application employs a method of reducing photon volume in epitaxial design (designing the resonant cavity length to be less than half a lasing wavelength), and sets the multi-quantum well structure at the wave crest position within the microcavity to obtain a larger optical confinement factor, thereby increasing the relaxation oscillation frequency.

[0070] In a second aspect, the present application also provides a light emitting assembly, which comprises the semiconductor laser as described in any of the preceding aspects. The light emitting assembly in the embodiment can be a TOSA (Transmitting Optical Sub-Assembley), which mainly realizes the conversion from electrical signal to optical signal. The light source (semiconductor light emitting diode or laser diode) is the core of the TOSA, and the LD chip, the monitoring photodiode (MD) and other components are packaged in a compact structure (TO coaxial package or butterfly package).

[0071] In a third aspect, the present application also provides an optical module, which comprises a light emitting module and a light receiving module, and the light emitting module adopts the light emitting assembly as described in the preceding aspect. The light receiving module in the embodiment is also called a ROSA (Resceiving Optical Sub-Assembley), and in a high data rate fiber module, a PIN or ADP photodiode and a TIA are assembled in a sealed metal shell.

[0072] The technical features of the above-mentioned embodiments can be combined in any manner. In order to make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described, however, as long as the combinations of the technical features do not exist contradictions, it should be considered that they are within the scope of the present application.

[0073] The above-mentioned embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, however, it should not be understood as a limitation on the scope of the patent. It should be pointed out that, for those skilled in the art, some modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A semiconductor laser, characterized by, The semiconductor laser comprises a resonant cavity structure, the resonant cavity structure comprises a resonant cavity for generating a standing wave, the resonant cavity is defined by a bottom mirror structure and a top mirror structure; The resonant cavity is provided with a multiple quantum well structure, the multiple quantum well structure is arranged at a wave peak position of the resonant cavity; The thickness of the resonant cavity is designed to be less than two-thirds of a lasing wavelength to improve the relaxation oscillation frequency of the semiconductor laser; The multiple quantum well structure comprises a tensile strain well layer, a compressive strain barrier layer, a compressive strain well layer, a tensile strain barrier layer, a tensile strain well layer, a compressive strain barrier layer and a tensile strain well layer arranged on the bottom mirror structure; The compressive strain well layer has a compressive strain of 2% and an indium component content of 0.12; the tensile strain barrier layer adjacent to the compressive strain well layer has a compressive strain of 3%; One of the tensile strain well layers in the multiple quantum well structure has a tensile strain of 2%, and the compressive strain barrier layer adjacent thereto has a compressive strain of 3%.

2. The semiconductor laser of claim 1, wherein, The thickness of the resonant cavity is between one lasing wavelength and two-thirds of a lasing wavelength; or The thickness of the resonant cavity is between one-half of a lasing wavelength and one lasing wavelength; or The thickness of the resonant cavity is less than or equal to one-half of a lasing wavelength.

3. The semiconductor laser of claim 1, wherein, The well layer and the barrier layer are respectively InGaAs and AlGaAs materials.

4. The semiconductor laser of claim 1, wherein Further comprising: An oxide confinement layer formed in the top mirror structure, the oxide confinement layer is arranged adjacent to the resonant cavity, and the oxide confinement layer is used to define a light emitting region of the semiconductor laser.

5. A light emitting assembly, characterized in that The light emitting assembly comprises the semiconductor laser according to any one of claims 1-4.

6. An optical module characterized by comprising: The optical transceiver comprises a light emitting module and a light receiving module, the light emitting module adopts the light emitting assembly according to claim 5.

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