Distributed feedback laser
By designing a periodic network structure on the upper waveguide layer of the distributed feedback laser, the problems of high cost and high loss in the prior art are solved, and efficient laser generation and stability improvement are achieved.
Patent Information
- Application Number
- CN202411889878.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-03-28
AI Technical Summary
The existing distributed feedback laser technology has the problem of high cost and high loss, which leads to low laser generation efficiency.
A distributed feedback laser with a periodic network structure is adopted on the upper waveguide layer. The contact surface of the network structure and the upper waveguide layer have a periodic metal structure to modulate the refractive index of light waves when propagating in the active area to avoid additional losses.
Without introducing additional losses, modulating the refractive index of the optical waves reduces the threshold current of the laser, improving the laser generation efficiency, reducing technical costs, and improving the stability of the laser.
Smart Images
Figure CN119726372A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of semiconductor lasers, and in particular to a distributed feedback laser. Background Art
[0002] At present, there are two main technologies for realizing distributed feedback lasers or DFB lasers (Distributed FeedBack in English). One is to use a buried network through refractive index modulation; the other is to use a surface metal network through gain modulation. The so-called "buried network" technology involves etching periodic network grooves after the growth of the active area of the semiconductor laser, and then completing the upper waveguide of the laser on top of the network through a new epitaxial growth step. However, the "buried network" technology requires interrupting the growth between the active area and the waveguide to etch the network, which is too difficult and costly to achieve; Another known technology for realizing distributed feedback lasers is "surface metallization network". In this technology, distributed feedback is obtained through loss modulation. This introduces additional losses, increases the threshold of the laser, and thus reduces its performance.
[0003] Therefore, in the current distributed feedback laser technology, there are problems of high cost and high loss, which in turn leads to the problem of low laser generation efficiency. Summary of the invention
[0004] Based on this, it is necessary to provide a distributed feedback laser to address the above technical issues.
[0005] In a first aspect, the present application provides a distributed feedback laser. The distributed feedback laser comprises:
[0006] A substrate; a semiconductor layer disposed on the substrate; the semiconductor layer includes an upper waveguide layer and a lower waveguide layer; an active region disposed between the upper waveguide layer and the lower waveguide layer; a network structure layer disposed on the upper waveguide layer;
[0007] The contact surface between the network structure layer and the upper waveguide layer is a periodic network structure, which is used to modulate the refractive index of the light wave when it propagates in the active area.
[0008] In one embodiment, the depth of the network structure is half of the thickness of the upper waveguide layer.
[0009] In one embodiment, the depth value of the network structure has a value range of:
[0010]
[0011] Among them, the is the depth value of the network structure; The unit depth value.
[0012] In one embodiment, the unit depth value is:
[0013]
[0014] in, The wavelength of the laser light generated by the distributed feedback laser; is the effective refractive index of the active area.
[0015] In one embodiment, the material of the network structure layer has a negative real dielectric constant.
[0016] In one of the embodiments, the material of the upper waveguide layer includes a first semiconductor material with a doping level less than a first predetermined doping level threshold.
[0017] In one embodiment, the material of the lower waveguide layer includes a second semiconductor material with a doping level greater than a second preset doping level threshold; the second preset doping level threshold is greater than the first preset doping level threshold.
[0018] In one embodiment, the distributed feedback laser further includes an ohmic contact layer; the ohmic contact layer is disposed on an upper surface of the upper waveguide layer.
[0019] In one embodiment, the active region has a first intrinsic refractive index; the first intrinsic refractive index is determined by material property parameters of a regional material of the active region.
[0020] In one of the embodiments, the active region has an effective refractive index; the effective refractive index is modulated based on the first intrinsic refractive index.
[0021] The above-mentioned distributed feedback laser comprises: a substrate; a semiconductor layer, arranged on the substrate; the semiconductor layer comprises an upper waveguide layer and a lower waveguide layer; an active region, arranged between the upper waveguide layer and the lower waveguide layer; a network structure layer, arranged on the upper waveguide layer; wherein the contact surface between the network structure layer and the upper waveguide layer has a periodic network structure, which is used to modulate the refractive index of the light wave when it propagates in the active region. In the distributed feedback laser provided by the embodiment of the present application, the network structure layer arranged on the upper waveguide layer can be a metal structure, the material of the upper waveguide layer is a semiconductor, and the contact surface between the network structure layer and the upper waveguide layer has a periodic network structure, which can modulate the refractive index of the light wave when it propagates in the active region without introducing additional losses, avoiding additional losses caused by the modulation method, reducing the threshold current of the laser, and thus improving the generation efficiency of the laser; and, no complicated growth interruption and epitaxial growth steps are required, which can further reduce the technical cost and improve the stability of the distributed laser. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 A schematic diagram of the structure of a distributed feedback laser provided in an embodiment of the present application. DETAILED DESCRIPTION
[0023] In order to make the purpose, technical solution and advantages of this application more clear, the following is a further detailed description of this application in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described here are only used to explain this application and do not limit the scope of protection of this application.
[0024] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.
[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.
[0026] In the present application, “first” and “second” do not represent specific quantities and orders, but are merely used to distinguish names.
[0027] In an exemplary embodiment, Figure 1 As shown, a distributed feedback laser is provided. The distributed feedback laser comprises:
[0028] A substrate; a semiconductor layer disposed on the substrate; the semiconductor layer comprises an upper waveguide layer (2) and a lower waveguide layer (3); an active region (1) disposed between the upper waveguide layer (2) and the lower waveguide layer (3); a network structure (5) layer (7) disposed on the upper waveguide layer (2);
[0029] The contact surface between the network structure (5) layer (7) and the upper waveguide layer (2) has a periodic network structure (5) for modulating the refractive index of the light wave (4) when propagating in the active region (1).
[0030] The substrate is disposed at the bottom of the distributed feedback laser, and is used to provide mechanical support for the distributed feedback laser and to carry other components of the laser. In one possible implementation, the substrate is made of materials including but not limited to InP, GaAs, GaSb, InAs and / or S i On the one hand, the substrate can indirectly affect the optical performance of the distributed feedback laser. The substrate itself does not directly participate in the light generation and transmission process, but the material properties of the substrate will indirectly affect the optical performance of the entire distributed feedback laser. Different substrate materials (e.g., InP, GaAs, GaSb, InAs and / or Si) have different thermal expansion coefficients, lattice constants and optical properties, etc. These properties will affect the crystal quality, stress state and interface properties between other semiconductor layers grown on the substrate (e.g., lower waveguide, active region (1) and upper waveguide). For example, if the lattice mismatch between the substrate material and the semiconductor layer grown on it is large, it may cause defects during the growth process. These defects will scatter light and increase light loss, thereby reducing the efficiency and performance of the laser. On the contrary, choosing a suitable substrate material can optimize the growth quality of the semiconductor layer, reduce defects, and improve the efficiency of light propagation inside the laser, which helps to achieve better optical performance, such as higher laser output power, narrower linewidth and better beam quality. In addition, the substrate can participate in thermal management. During the operation of the distributed feedback laser, heat is generated, and the substrate also plays a certain role in thermal management. As part of the laser structure, it participates in the conduction and diffusion of heat.
[0031] A semiconductor layer is provided on a substrate; the semiconductor layer comprises an upper waveguide layer (2) and a lower waveguide layer (3); the material of the upper waveguide layer (2) comprises a first semiconductor material with a doping degree less than a first preset doping degree threshold, the first semiconductor material including but not limited to InP, InGaAs and / or AlGaAs; based on the first semiconductor material of the upper waveguide layer (2), the material of the upper waveguide layer (2) has a second intrinsic refractive index, the second intrinsic refractive index is determined by the material of the upper waveguide layer (2), i.e., the first semiconductor material; the doping degree of the first semiconductor material of the upper waveguide layer (2) is less than the first preset doping degree threshold, indicating that the first semiconductor material of the upper waveguide layer (2) is undoped or has a low doping degree; in this case, the second intrinsic refractive index of the upper waveguide layer (2) changes by less than about ten percent. Furthermore, the distributed feedback laser also includes an ohmic contact layer, which is a thin layer of highly doped semiconductor material disposed on the upper waveguide layer (2). The main function of the ohmic contact layer is to achieve good electrical connection, so that the external current can be effectively injected into the active region (active region (1)) of the laser, and provide the necessary energy for achieving population inversion. The surface characteristics and structural stability of the upper waveguide have an important influence on the quality and performance of the ohmic contact layer. For example, a flat, clean upper waveguide surface with good compatibility with the ohmic contact layer material helps to form a low-resistance ohmic contact, reduce energy loss and heat generation during current injection, improve the electrical efficiency of the laser, and ensure that the laser can stably obtain the required energy input during operation, thereby ensuring stable generation and output of the laser. The material of the lower waveguide layer (3) comprises a second semiconductor material with a doping degree greater than a second preset doping degree threshold, the second semiconductor material comprises InP, based on the second semiconductor material of the lower waveguide layer (3), the material of the lower waveguide layer (3) has a third intrinsic refractive index, the third intrinsic refractive index is determined by the material of the lower waveguide layer (3), that is, the second semiconductor material, the doping degree of the second semiconductor material of the lower waveguide layer (3) is greater than the second preset doping degree threshold, indicating that the doping degree of the second semiconductor material of the lower waveguide layer (3) is relatively high.
[0032] The active region (1) is arranged between the upper waveguide layer (2) and the lower waveguide layer (3); the active region (1) has a first intrinsic refractive index; the first intrinsic refractive index is determined by the material characteristic parameters of the region material of the active region (1); the structure of the active region (1) is a multi-layer stack; the materials of the multi-layer stack structure include but are not limited to GaAs and AlGaAs, AlInAs and GaInAs, or InAs and AlSb. The active region (1) can be used for laser generation and light wave (4) propagation. First, the active region (1) is the main place for light wave (4) propagation, and can guide light wave (4) with a predetermined laser wavelength (4) length to propagate therein. The light wave (4) is transmitted along a specific path in the active region (1), and its propagation characteristics are affected by the refractive index of the material of the active region (1). For example, a suitable refractive index helps to achieve effective confinement and transmission of the light wave (4), reduce light scattering and loss, and provide necessary conditions for laser generation and amplification. Secondly, in the active region (1), an inversion distribution of the particle population can be achieved through an external excitation source (such as current injection). That is, the number of particles at the high energy level is greater than the number of particles at the low energy level, which gives the particles at the high energy level more opportunities to transition to the low energy level and emit photons with a wavelength corresponding to the energy level difference (i.e., the predetermined laser wavelength (4)). These emitted photons are continuously amplified in the active region (1), forming stimulated radiation, thereby generating laser light. The material composition and structural design of the active region (1) are crucial to achieving efficient particle population inversion and stable laser emission. For example, a multilayer stacked structure composed of GaAs and AlGaAs, AlInAs and GaInAs, or InAs and AlSb can optimize the energy level structure and improve the particle population inversion efficiency by reasonably designing the thickness of each layer, doping concentration and other parameters, thereby enhancing the ability to generate laser light. In addition, the active region (1) can also cooperate with other components of the distributed feedback laser. First, coupling with the waveguide: the active region (1) is tightly coupled with the upper waveguide and the lower waveguide, and together they form a light transmission channel. The refractive index of the active region (1) matches the refractive index of the waveguide, so that the light wave (4) can be smoothly transmitted between different components, reducing interface reflection and loss. For example, when the light wave (4) enters the upper waveguide or the lower waveguide from the active region (1), the appropriate refractive index matching can ensure that the energy of the light is effectively transferred to the waveguide, continues to propagate and participates in subsequent optical processes, such as interacting with the gas in the photoacoustic cell detection system to generate a photoacoustic signal (if the laser is applied to such a system). Second, other components can cooperate to modulate the refractive index of the light wave (4) when it propagates in the active region (1), that is, modulate the first intrinsic refractive index of the active region (1) to an effective refractive index. In addition, the material composition and energy level structure of the active region (1) directly determine the operating wavelength of the laser.Different material combinations have different band structures, corresponding to different energy level differences, which determine the wavelength range in which laser light can be generated. By selecting suitable materials to construct the active region (1), laser output of a specific wavelength can be achieved to meet the needs of different application scenarios. For example, in the field of optical communications, laser light of a specific wavelength (e.g., 1550nm) may be required for long-distance transmission. In this case, suitable materials can be selected to design the active region (1) so that it can generate laser light of this wavelength. Furthermore, factors such as the efficiency of population inversion in the active region (1), the absorption and emission characteristics of light, etc., will affect the overall efficiency and output power of the laser.
[0033] The network structure (5) layer (7) is arranged on the upper waveguide layer (2); the contact surface between the network structure (5) layer (7) and the upper waveguide layer (2) is a periodic network structure (5), and the network structure (5) can be used to modulate the refractive index of the light wave (4) when propagating in the active area (1), and can modulate the first intrinsic refractive index in the active area (1) to an effective refractive index. The period of the network structure (5) is Λ. In a possible implementation, the material of the network structure (5) layer (7) can be a material having a negative real dielectric constant, for example, a metal structure. The depth value of the network structure (5) is half of the thickness value of the upper waveguide layer (2). The value range of the depth value of the network structure (5) can refer to formula (1):
[0034]
[0035] Among them, the is the depth value of the network structure (5); is the unit depth value. The relationship between the unit depth value, laser wavelength and effective refractive index can be seen in formula (2);
[0036]
[0037] in, The wavelength of the laser light generated by the distributed feedback laser; is the effective refractive index of the active area (1).
[0038] The contact surface between the network structure (5) layer (7) and the upper waveguide layer (2) is a periodic network structure (5). Based on the network structure (5), when the light wave (4) propagates in the active region (1) and reaches the upper waveguide, it interacts with the network structure (5) layer (7). Due to the difference in optical properties between metal and semiconductor materials, this interaction will change the propagation characteristics of the light wave (4) in the waveguide, thereby achieving modulation of the effective refractive index of the active region (1). For example, the presence of metal will affect the local electromagnetic field distribution, causing the equivalent refractive index of the waveguide to change, and this change will be transmitted to the active region (1), changing the propagation speed and phase of the light wave (4) in the active region (1). The depth of the network structure (5) is the key to achieving effective refractive index modulation and can have an important impact on the effective refractive index modulation. When the depth is within this range, the effective refractive index of the active region (1) can be appropriately changed without introducing additional losses (for example, loss modulation in traditional surface metal network technology will introduce additional losses), thereby creating conditions for obtaining stable and controlled distributed feedback. For example, if the depth is too shallow, sufficient refractive index modulation may not be produced, resulting in weak distributed feedback; while if the depth is too deep, unnecessary losses or other adverse effects may be introduced, destroying the performance of the laser. Further, through refractive index modulation, the distributed feedback mechanism of the distributed feedback laser can be realized. Through refractive index modulation, the network structure (5) layer (7) allows the light wave (4) to propagate in the waveguide, and part of the light will be reflected back to the active region (1) to form feedback. This feedback interacts with the laser being generated, and only light with a specific frequency and phase can form a stable oscillation in the cavity, while light with other frequencies and phases is suppressed. Due to the precise design of parameters such as the periodicity and depth of the network structure (5) layer (7), this feedback process is stable and controlled, and can achieve effective selection of the laser mode, so that the laser outputs a laser with a specific wavelength, narrow linewidth, and high coherence. The network structure (5) layer (7) works together with the upper waveguide, the active region (1) and the lower waveguide to form the core structure of the distributed feedback laser.
[0039] The distributed feedback laser provided in this embodiment comprises: a substrate; a semiconductor layer disposed on the substrate; the semiconductor layer comprises an upper waveguide layer (2) and a lower waveguide layer (3); an active region (1) disposed between the upper waveguide layer (2) and the lower waveguide layer (3); and a network structure (5) layer (7) disposed on the upper waveguide layer (2); wherein the contact surface between the network structure (5) layer (7) and the upper waveguide layer (2) has a periodic network structure (5) for modulating the refractive index of a light wave (4) when propagating in the active region (1). In the distributed feedback laser provided in the embodiment of the present application, the network structure (5) layer (7) arranged on the upper waveguide layer (2) can be a metal structure, the material of the upper waveguide layer (2) is a semiconductor, and the contact surface between the network structure (5) layer (7) and the upper waveguide layer (2) has a periodic network structure (5). The network structure (5) can modulate the refractive index of the light wave (4) when propagating in the active area (1) without introducing additional loss, thereby avoiding additional loss caused by the modulation method, reducing the threshold current of the laser, and further improving the laser generation efficiency; and, no complicated growth interruption and epitaxial growth steps are required, which can further reduce the technical cost and improve the stability of the distributed laser.
[0040] In an exemplary embodiment, the depth of the network structure (5) is half of the thickness of the upper waveguide layer (2), for example, 0.5 μm.
[0041] In an exemplary embodiment, the range of the depth value of the network structure (5) can be found in formula (1):
[0042]
[0043] Among them, the is the depth value of the network structure (5); The unit depth value.
[0044] In an exemplary embodiment, the relationship between the unit depth value of the network structure (5) and the laser wavelength and the effective refractive index can be seen in equation (2);
[0045]
[0046] in, The wavelength of the laser light generated by the distributed feedback laser; is the effective refractive index of the active area (1).
[0047] The depth of the network structure (5) is the key to achieving effective refractive index modulation. When the depth is within this range, the effective refractive index of the active region (1) can be appropriately changed without introducing additional losses (for example, loss modulation in traditional surface metal network technology will introduce additional losses), thereby creating conditions for obtaining stable and controlled distributed feedback. For example, if the depth is too shallow, sufficient refractive index modulation effect may not be generated, resulting in weak distributed feedback; while if the depth is too deep, unnecessary losses or other adverse effects may be introduced, destroying the performance of the laser.
[0048] In the distributed feedback laser provided in this embodiment, the network structure (5) can modulate the refractive index of the light wave (4) when propagating in the active region (1) without introducing additional losses, thereby avoiding additional losses caused by the modulation method, reducing the threshold current of the laser, and further improving the laser generation efficiency; and, without requiring complicated growth interruption and epitaxial growth steps, the technical cost can be further reduced and the stability of the distributed laser can be improved.
[0049] In an exemplary embodiment, the material of the network structure (5) layer (7) has a negative real dielectric constant. For example, the material having a negative real dielectric constant can be a metal material. The contact surface between the network structure (5) layer (7) and the upper waveguide layer (2) is a periodic network structure (5). Based on the network structure (5), when the light wave (4) propagates in the active area (1) and reaches the upper waveguide, it will interact with the network structure (5) layer (7). Due to the difference in optical properties between metal and semiconductor materials, this interaction will change the propagation characteristics of the light wave (4) in the waveguide, thereby achieving modulation of the effective refractive index of the active area (1). For example, the presence of metal will affect the local electromagnetic field distribution, causing the equivalent refractive index of the waveguide to change, and this change will be transmitted to the active area (1), changing the propagation speed and phase of the light wave (4) in the active area (1).
[0050] In an exemplary embodiment, the material of the upper waveguide layer (2) comprises a first semiconductor material with a doping level less than a first preset doping level threshold.
[0051] The first semiconductor material includes but is not limited to InP, InGaAs and / or AlGaAs. Based on the first semiconductor material of the upper waveguide layer (2), the material of the upper waveguide layer (2) has a second intrinsic refractive index, which is determined by the material of the upper waveguide layer (2), i.e., the first semiconductor material. The doping degree of the first semiconductor material of the upper waveguide layer (2) is less than a first preset doping degree threshold, indicating that the first semiconductor material of the upper waveguide layer (2) is undoped or has a low doping degree. In this case, the second intrinsic refractive index of the upper waveguide layer (2) changes by less than about ten percent. Based on the first semiconductor material, the upper waveguide layer (2) can work in conjunction with the active region (1) and the lower waveguide to ensure that the light wave (4) can be efficiently transmitted in the entire laser structure. After being generated from the active region (1), the light wave (4) enters the upper waveguide and propagates along its specific structure, reducing the scattering and loss of light during propagation, so that the light can reach other parts of the laser with lower energy loss, such as interacting with the gas in the photoacoustic cell to generate photoacoustic signals in some applications, or transmitting to external devices such as optical fibers in laser communication systems; combined with the structural design (e.g., thickness and shape, etc.) of the upper waveguide layer (2), the upper waveguide can precisely control the propagation direction of the light wave (4). This helps to guide the light to the required position in the laser, such as guiding it to the area that interacts with the surface metal network structure (5) to achieve effective modulation of the light. Appropriate propagation direction control can improve the optical efficiency of the laser, ensure that the light can participate in the laser generation and modulation process to the greatest extent during the transmission process inside the laser, and reduce unnecessary energy loss and optical interference. In addition, based on the first semiconductor material and the contact surface between the network structure (5) layer (7) and the upper waveguide layer (2) having the periodic network structure (5), the first semiconductor material and the metal material of the network structure (5) layer (7) have differences in optical properties, which changes the propagation properties of the light wave (4) in the waveguide, thereby modulating the refractive index of the light wave (4) when propagating in the active area (1), and modulating the first intrinsic refractive index in the active area (1) to an effective refractive index.
[0052] In an exemplary embodiment, the material of the lower waveguide layer (3) comprises a second semiconductor material having a doping level greater than a second preset doping level threshold; the second preset doping level threshold is greater than the first preset doping level threshold.
[0053] Based on the material of the lower waveguide layer (3), i.e., the second semiconductor material, and the structure, the lower waveguide layer (3) has the following functions: (1) constructing an optical transmission path: the lower waveguide, the upper waveguide and the active region (1) together form a complete optical transmission channel. It provides a low-loss path for the propagation of the light wave (4) inside the laser, ensuring that the light generated from the active region (1) can be effectively transmitted to other parts of the laser, or form a stable optical oscillation circuit inside the laser. The light wave (4) propagates along a specific direction in the lower waveguide, and its propagation characteristics are affected by the refractive index and structural parameters (such as thickness, shape, etc.) of the lower waveguide material. By reasonably designing the refractive index and structure of the lower waveguide, it is possible to achieve good optical matching with the upper waveguide and the active region (1), reduce the reflection and refraction loss of light at the interface of different components, make the transmission of light in the entire laser structure smoother, and improve the light transmission efficiency, thereby helping to improve the overall performance of the laser, such as output power and beam quality. (2) Control of light field distribution: The presence of the lower waveguide helps to control the field distribution of light in the active region (active region (1)) of the laser. By working in synergy with the upper waveguide, it can constrain the propagation of light in the vertical direction, so that the light can interact with the gain medium more concentratedly in the active region (1), enhance the efficiency of the interaction between light and matter, improve the efficiency of the population inversion, and thus facilitate the generation and amplification of lasers. For example, the appropriate design of the thickness and refractive index of the lower waveguide can make the light field form a distribution pattern in the active region (1) that is more conducive to laser generation, such as making the light field more evenly distributed in the active layer of the active region (1), avoiding problems such as local overheating or insufficient light absorption caused by excessive concentration or dispersion of the light field, thereby optimizing the performance of the laser and improving the generation efficiency and stability of the laser. (3) Influence of current distribution: The material properties and structure of the lower waveguide have a certain influence on the current distribution inside the laser. In a current injection distributed feedback laser, the current needs to be effectively transmitted to the active region (1) through structures such as the lower waveguide to achieve population inversion. The electrical parameters of the lower waveguide, such as the conductivity, will affect the conduction process of the current therein, and thus affect the uniformity of the current distribution in the active area (1). In addition, during the operation of the laser, heat will be generated, and the lower waveguide also plays a role in heat conduction and heat dissipation. As a part of the laser structure, it participates in the process of heat conduction from the active area (1) to the outside. The thermal properties of the lower waveguide material, such as the thermal conductivity, determine its ability to conduct heat. Good thermal conductivity helps to dissipate the heat generated in the active area (1) in a timely manner and maintain the temperature stability of the various components of the laser.
[0054] In an exemplary embodiment, the distributed feedback laser further comprises an ohmic contact layer; the ohmic contact layer is arranged on the upper surface of the upper waveguide layer (2).
[0055] The laser includes a thin layer of highly doped semiconductor material on the surface of the upper waveguide as an ohmic contact layer, the thickness of which is about 100 nm, and the upper waveguide provides a physical basis for the formation of the ohmic contact layer. The main function of the ohmic contact layer is to achieve good electrical connection, so that the external current can be effectively injected into the active region (active region (1)) of the laser, and provide the necessary energy for achieving population inversion. The surface characteristics and structural stability of the upper waveguide have an important influence on the quality and performance of the ohmic contact layer. For example, a flat, clean upper waveguide surface with good compatibility with the ohmic contact layer material helps to form a low-resistance ohmic contact, reduce energy loss and heat generation during current injection, improve the electrical efficiency of the laser, and ensure that the laser can stably obtain the required energy input during operation, thereby ensuring stable generation and output of the laser.
[0056] In an exemplary embodiment, the active region (1) has a first intrinsic refractive index; the first intrinsic refractive index is determined by material property parameters of a region material of the active region (1).
[0057] In an exemplary embodiment, the active region (1) has an effective refractive index; the effective refractive index is modulated based on the first intrinsic refractive index.
[0058] The contact surface between the network structure (5) layer (7) and the upper waveguide layer (2) is a periodic network structure (5), and the network structure (5) can be used to modulate the refractive index of the light wave (4) when propagating in the active area (1), and can modulate the first intrinsic refractive index in the active area (1) to an effective refractive index. The effective refractive index is the actual refractive index of the light wave (4) when propagating in the active area (1).
[0059] In the distributed feedback laser provided in this embodiment, the network structure (5) layer (7) provided on the upper waveguide layer (2) can be a metal structure, the material of the upper waveguide layer (2) is a semiconductor, and the contact surface between the network structure (5) layer (7) and the upper waveguide layer (2) has a periodic network structure (5). The network structure (5) can modulate the refractive index of the light wave (4) when propagating in the active area (1) without introducing additional loss, thereby avoiding additional loss caused by the modulation method, reducing the threshold current of the laser, and further improving the laser generation efficiency; and, no complicated growth interruption and epitaxial growth steps are required, which can further reduce the technical cost and improve the stability of the distributed laser.
[0060] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.
[0061] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.
Claims
1. A distributed feedback laser, characterized in that: include: substrate; A semiconductor layer, disposed on the substrate; the semiconductor layer comprises an upper waveguide layer and a lower waveguide layer; an active region disposed between the upper waveguide layer and the lower waveguide layer; A network structure layer, disposed on the upper waveguide layer; The contact surface between the network structure layer and the upper waveguide layer is a periodic network structure, which is used to modulate the refractive index of the light wave when it propagates in the active area.
2. The distributed feedback laser according to claim 1, characterized in that: The depth of the network structure is half of the thickness of the upper waveguide layer.
3. The distributed feedback laser according to claim 2, characterized in that: The depth value of the network structure has a value range of: Among them, the is the depth value of the network structure; The unit depth value.
4. The distributed feedback laser according to claim 3, characterized in that: The unit depth value is: in, The wavelength of the laser light generated by the distributed feedback laser; is the effective refractive index of the active area.
5. The distributed feedback laser according to claim 1, characterized in that: The material of the network structure layer has a negative real dielectric constant.
6. The distributed feedback laser according to claim 1, characterized in that: The material of the upper waveguide layer includes a first semiconductor material with a doping level less than a first preset doping level threshold.
7. The distributed feedback laser according to claim 6, characterized in that: The material of the lower waveguide layer includes a second semiconductor material with a doping level greater than a second preset doping level threshold; the second preset doping level threshold is greater than the first preset doping level threshold.
8. The distributed feedback laser according to claim 1, characterized in that: The distributed feedback laser further comprises an ohmic contact layer; the ohmic contact layer is arranged on the upper surface of the upper waveguide layer.
9. The distributed feedback laser according to claim 1, characterized in that: The active region has a first intrinsic refractive index; the first intrinsic refractive index is determined by material characteristic parameters of a region material of the active region.
10. The distributed feedback laser according to any one of claims 1 to 9, characterized in that: The active region has an effective refractive index; the effective refractive index is modulated based on the first intrinsic refractive index.