CN118801210A - A high-power anti-reflection semiconductor laser - Google Patents

Abstract

The invention discloses a high-power anti-reflection semiconductor laser, which belongs to the technical field of laser design and comprises an N-surface metal layer, a substrate layer, a buffer layer, a lower limiting layer, a multiple quantum well layer, an upper limiting layer, a lower spacing layer, a lower grating layer, an upper spacing layer, an upper grating layer, a filling layer, a cover layer, a contact layer, a passivation layer and a P-surface metal layer from bottom to top in sequence; the laser is divided into a first mode selection area and a second mode selection area along the length direction of the laser cavity; the first mode selection area and the second mode selection area are respectively arranged on the lower grating layer and the upper grating layer to manufacture distributed feedback grating structures. The laser can improve the anti-reflection light capability of the laser and reduce the influence of the reflection light on the working state of the laser.

Description

A high-power anti-reflection semiconductor laser

Technical Field

The invention belongs to the technical field of laser design, and in particular relates to a high-power anti-reflection semiconductor laser.

Background Art

With the explosive growth of data center traffic, the demand for high-speed transmission is also increasing. Silicon-based modulators can support data transmission rates of up to tens of Gbps or even hundreds of Gbps. This is crucial for data centers to cope with the needs of massive data processing and transmission, and can significantly improve the overall bandwidth and data transmission efficiency of data centers. Silicon-based modulators are compatible with mature CMOS manufacturing processes, have small size, high integration, fast response time and high linearity, and can provide high-quality signal modulation. However, since silicon is an indirect bandgap semiconductor with low luminescence efficiency, it cannot be directly used to make high-performance light sources.

InP lasers can generate light in the 1.3-micron and 1.55-micron wavelength bands, which happen to be the low-loss windows for optical fiber communications and are very suitable for high-speed optical communications.

In optical modules, it is often necessary to place an optical isolator between a high-power laser and a silicon-based modulator to prevent reflected light from causing changes in the laser's spectral quality, output power, line width and other characteristics, thereby causing degradation of the optical module's modulated signal. Traditional high-power DFB lasers have a low anti-reflection threshold due to their simple structure and high output optical power. The introduction of isolators increases the packaging cost of optical modules, so improving the anti-reflection threshold of DFB lasers is of great significance for optical modules required by data centers.

The patent application with the publication number CN115912049A discloses a distributed feedback laser and its preparation method, wherein the laser comprises: a laser epitaxial structure, the laser epitaxial structure comprises a substrate and a multi-layer epitaxial layer located on one side of the substrate; a first electrode layer located on the side of the epitaxial layer away from the substrate; wherein the multi-layer epitaxial layer comprises at least one grating resonant cavity structure, the grating resonant cavity structure comprises a first grating structure, a resonant cavity structure and a second grating structure sequentially arranged along a first direction; the grating period of the first grating structure and the second grating structure is different from the grating period of the resonant cavity structure, and the first grating structure, the resonant cavity structure and the second grating structure have only one common lasing mode; and a second electrode layer located on the side of the substrate away from the epitaxial layer. It can reduce the optical loss of the device, improve the optical coupling efficiency and suppress multi-mode lasing, but its grating structure is complex and the anti-reflection light capability is limited, which cannot meet the requirements of practical application and promotion.

Summary of the invention

In view of the shortcomings of the prior art, the present invention aims to provide a high-power anti-reflection semiconductor laser with a high reflection light threshold. The laser can improve the anti-reflection light capability of the laser and reduce the influence of the reflected light on the working state of the laser.

In order to achieve the above object, the present invention adopts the following technical solutions:

The present invention provides a high-power anti-reflection semiconductor laser, which comprises, from bottom to top, an N-face metal layer, a substrate layer, a buffer layer, a lower confinement layer, a multi-quantum well layer, an upper confinement layer, a lower spacer layer, a lower grating layer, an upper spacer layer, an upper grating layer, a filling layer, a cap layer, a contact layer, a passivation layer and a P-face metal layer;

Along the length direction of the laser cavity, the laser is divided into a first mode selection area and a second mode selection area; the first mode selection area and the second mode selection area are respectively made of distributed feedback grating structures in the lower grating layer and the upper grating layer.

As a further improvement of the present invention, the distributed feedback grating structure on the lower grating layer and the distributed feedback grating structure on the upper grating layer do not overlap in a vertical projection direction.

As a further improvement of the present invention, the thickness, composition and grating period of the lower grating layer and the upper grating layer are the same or different.

As a further improvement of the present invention, the thickness of the lower grating layer and the upper grating layer is 10nm-100nm.

As a further improvement of the present invention, the doping concentration of the distributed feedback grating structure of the lower grating layer and the upper grating layer is 4e ¹⁷ /cm ³ to 1e ¹⁸ /cm ³ , and the luminous wavelength of the material is 1.0 μm to 1.3 μm.

As a further improvement of the present invention, the cavity length of the laser is 200 μm to 5000 μm.

As a further improvement of the present invention, the electrode patterns of the P-side metal layers in the first mode selection area and the second mode selection area are integrated as a whole, or electrical isolation grooves are made by etching the cap layer and the contact layer, and the P-side metal layer is patterned and isolated.

As a further improvement of the present invention, the high-power anti-reflection semiconductor laser is a buried heterojunction waveguide or a ridge waveguide.

As a further improvement of the present invention, the number of pairs of multi-quantum well layers is 2 to 10 pairs.

As a further improvement of the present invention, the N-side metal layer is an AuGeNi/Au alloy layer, the substrate layer is an n-type InP substrate, the buffer layer is Si-doped n-type InP, the lower limiting layer is an InGaAsP or InGaAlAs layer, the multiple quantum well layer is InGaAsP or InGaAlAs, the upper limiting layer is InGaAsP or InGaAlAs, the lower spacer layer is InP, the lower grating layer is InGaAsP, the upper spacer layer is InP, the upper grating layer is InGaAsP, the filling layer is InP, the cap layer is Zn-doped InP, the contact layer is Zn-doped InGaAs, the passivation layer is SiO or SiNx, and the P-side metal layer is a Ti/Pt/Au alloy.

Compared with the prior art, the present invention has the following beneficial effects:

The DFB laser is divided into a first mode selection area and a second mode selection area. By introducing a double grating layer, specifically, the first mode selection area and the second mode selection area are respectively made into a distributed feedback grating structure on the lower grating layer and the upper grating layer. Without increasing the complexity of the laser structure, the anti-reflection light capability of the laser can be improved, and the influence of the reflected light on the working state of the laser can be reduced. There is no need to add an isolator in the optical module, which can greatly reduce the packaging difficulty and packaging cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a high-power anti-reflection semiconductor laser provided by the present invention.

DETAILED DESCRIPTION

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the 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.

In this application, the term "and/or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and/or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character "/" generally indicates that the associated objects are in an "or" relationship.

In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, c can be single or multiple, respectively.

It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass in the embodiment description of the present application can be μg, mg, g, kg and other mass units known in the chemical industry.

The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

The first object of the present invention is to provide a high-power anti-reflection semiconductor laser, and more particularly to a design of a high-power reflective semiconductor laser with a high anti-reflection light threshold, as shown in FIG1 , which includes, from bottom to top, an N-side metal layer 01, a substrate layer 02, a buffer layer 03, a lower confinement layer 04, a multi-quantum well layer 05, an upper confinement layer 06, a lower spacer layer 07, a lower grating layer 08, an upper spacer layer 09, an upper grating layer 10, a filling layer 11, a cap layer 12, a contact layer 13, a passivation layer 14 and a P-side metal layer 15.

The main functions of each structural layer of the laser structure are as follows:

The N-side metal layer 01 is usually used as a back electrode to provide a channel for current injection for the laser, and requires good conductivity and adhesion to the substrate layer.

The function of the substrate layer 02 is to provide mechanical support and electrical connection for the laser, and it needs to have good thermal stability and mechanical strength.

The function of the buffer layer 03 is to reduce the lattice mismatch and thermal stress between the substrate layer and the subsequent functional layer, and to improve the stability of the overall structure. It is necessary to have good lattice matching and thermal expansion coefficient.

The function of the lower confinement layer 04 is to limit the lateral diffusion of carriers (electrons and holes) and improve the luminous efficiency. It is necessary to have a good energy band structure and carrier confinement capability.

The function of the multi-quantum well layer 05 is to serve as the active layer of the laser, realize the recombination of electrons and holes, and generate photons. It is usually composed of multiple quantum wells, and the energy level structure of each quantum well determines the emission wavelength of the laser.

The upper confinement layer 06 is used to form a three-dimensional confinement structure of carriers together with the lower confinement layer to improve the luminous efficiency. Similar to the lower confinement layer, it needs to have a good energy band structure and carrier confinement capability.

The lower spacer layer 07 and the upper spacer layer 09 are respectively located between the lower grating layer 08 and the upper grating layer 10, and are used to adjust the performance of the grating layer. Appropriate materials and thicknesses need to be selected according to specific requirements.

The lower grating layer 08 and the upper grating layer 10 form lateral waveguides for photons, realize lateral confinement and optical feedback of photons, and promote the generation of lasers. They need to have good optical properties and compatibility with adjacent layers.

The filling layer 11 and the cover layer 12 are used to fill and protect the internal structure of the laser, improve the stability and reliability of the laser, and also need to have good chemical stability and mechanical strength.

The contact layer 13 is used to provide a channel for current injection and to form an electrical connection with the P-side metal layer 15. It needs good conductivity and adhesion to the cap layer.

The function of the passivation layer 14 is to protect the internal structure of the laser and prevent the external environment from corroding and damaging the laser. It needs to have good chemical stability and electrical insulation.

The P-side metal layer 15 serves as the upper electrode of the laser and forms a current injection channel together with the N-side metal layer 01. It needs good conductivity and adhesion to the contact layer.

As an improvement of the present invention, in order to achieve a high-power anti-reflection effect, the laser is divided into a first mode selection area 100 and a second mode selection area 200 along the laser cavity length direction; wherein the first mode selection area 100 and the second mode selection area 200 respectively make distributed feedback grating structures in the lower grating layer 08 and the upper grating layer 10;

As an example, the present invention divides the DFB laser into a first mode selection area 100 and a second mode selection area 200. By introducing a double grating layer, the first mode selection area 100 and the second mode selection area 200 respectively make distributed feedback grating structures in the lower grating layer 08 and the upper grating layer 10. Without increasing the complexity of the laser structure, the anti-reflection light capability of the laser can be improved, and the influence of the reflected light on the working state of the laser can be reduced. It is not necessary to add an isolator in the optical module, which can greatly reduce the packaging difficulty and packaging cost. In this way, the reflection loss of light at the end face of the laser is reduced, and the output power and efficiency of the laser are improved.

This high-power anti-reflection semiconductor laser achieves effective carrier confinement and efficient photon generation and transmission through a designed multi-layer structure, while also using an anti-reflection design to improve laser performance.

In particular, the distributed feedback grating structure is fabricated on the first mode selection region 100 (lower grating layer 08) and the second mode selection region 200 (upper grating layer 10). The distributed feedback grating structure can provide strong optical feedback at a specific wavelength, thereby enhancing the mode selection capability of the laser. By fabricating the grating structure on the lower grating layer 08 and the upper grating layer 10, respectively, more precise mode selection and optical feedback control can be achieved, thereby improving the performance of the laser.

The distributed feedback grating structure of the present invention helps to stabilize the output wavelength and power of the laser and reduce fluctuations and drifts. The coordinated use of the upper and lower grating structures can further improve the stability and reliability of the laser, ensuring that it can stably output high-quality lasers under various working conditions. The selective feedback effect of the distributed feedback grating structure ensures that only the longitudinal modes that meet specific conditions can oscillate and output in the laser.

Furthermore, by optimizing the design of the grating structure, single longitudinal mode narrow linewidth output can be achieved to meet the needs of applications such as high-precision spectral analysis and communications. The distributed feedback grating structure can effectively reduce the reflection loss of light at the end face of the laser and improve the optical power conversion efficiency of the laser.

During the preparation process, the electrodes of the first mode selection area 100 and the second mode selection area 200 of the laser can be a whole, or the P-side metal layer 15 can be pattern-separated and isolated by etching the cap layer 12 and the contact layer 13 to make electrical isolation grooves.

At the same time, by optimizing the parameters of the grating structure (such as duty cycle, grating period, etc.), the output power and efficiency of the laser can be further improved. The distributed feedback grating structure allows the longitudinal mode position that meets the conditions to be tuned by changing its effective refractive index or modulation period. This enables the laser to have stronger wavelength tuning capabilities and can adapt to application scenarios with different wavelength requirements.

Therefore, the high-power anti-reflection semiconductor laser with distributed feedback grating structure made in the first mode selection area 100 and the second mode selection area 200 respectively has the advantages of enhancing optical feedback and mode selection, improving stability and reliability, achieving single longitudinal mode narrow linewidth output, increasing output power, enhancing wavelength tuning capability and simplifying structure. These advantages make the laser have broad application prospects in the fields of spectral analysis, communication, sensing, etc.

As a specific scheme, the present invention provides a specific high-power anti-reflection semiconductor laser structure, wherein the N-side metal layer 01 is an AuGeNi/Au alloy layer, the substrate layer 02 is an n-type InP substrate, the buffer layer 03 is Si-doped n-type InP, the lower limiting layer 04 is an InGaAsP or InGaAlAs layer, the multiple quantum well layer 05 is InGaAsP or InGaAlAs, the upper limiting layer 06 is InGaAsP or InGaAlAs, the lower spacer layer 07 is InP, the lower grating layer 08 is InGaAsP, the upper spacer layer 09 is InP, the upper grating layer 10 is InGaAsP, the filling layer 11 is InP, the cap layer 12 is Zn-doped InP, the contact layer 13 is Zn-doped InGaAs, the passivation layer is SiO2 or SiNx, and the P-side metal layer 15 is Ti/Pt/Au.

Of course, this solution is a preferred solution and is not a specific limitation of the present invention. Other materials can also be used to make anti-reflection semiconductor lasers. The present application does not make any specific limitation on the replacement of specific materials.

Optionally, the typical thickness of the lower grating layer 08 and the upper grating layer 10 is 10nm~100nm, and the specific thickness can be 10nm~80nm, 50nm~100nm, 30nm~70nm, 10nm, 30nm, 50nm, 70nm, 80nm, 90nm, 100nm, etc. The doping concentration is 4e ¹⁷ /cm ³ to 1e ¹⁸ /cm ³ , and the doping concentration can be 1e ¹⁸ /cm ³ to 1e ¹⁸ /cm ³ , 5e ¹⁷ /cm ³ to 1e ¹⁸ /cm ³ , 9e ¹⁷ /cm ³ to 1e ¹⁸ /cm ³ , 4e ¹⁷ /cm ³ , 6e ¹⁷ /cm ³ , 8e ¹⁷ /cm ³ , 9e ¹⁷ /cm ³ , 1e ¹⁸ /cm ³ , 4e ¹⁷ /cm ³ , etc. The luminous wavelength of the material is 1.0μm to 1.3μm, specifically 1.1μm to 1.3μm, 1.0μm to 1.2μm, 1.0μm, 1.2μm, 1.25μm, 1.15μm, 1.3μm, etc.

By adopting the structure of the present invention, the final laser cavity length is 200 μm to 5000 μm. Therefore, the overall anti-reflection semiconductor laser has a small volume, which is convenient for later application.

As an example, the thickness, composition and grating period of the lower grating layer 08 and the upper grating layer 10 of the present invention may be the same or different.

Normally, the number of pairs of multi-quantum well layers is 2 to 10 pairs. This application may also select this range. According to actual needs, it can also be 5 to 10 pairs, 4 to 8 pairs, 5 to 10 pairs, 2 pairs, 5 pairs, 6 pairs, 8 pairs, 9 pairs, 10 pairs, etc.

Example

The invention provides a high-power anti-reflection semiconductor laser, comprising an n-type InP substrate, an n-type InP buffer layer, an n-InGaAsP or InGaAlAs lower limiting layer, an InGaAsP or InGaAlAs multi-quantum well MQW active layer, a p-InGaAsP or InGaAlAs upper limiting layer, a p-type InP lower spacer layer, a p-type InGaAsP lower grating layer, a p-type InP upper spacer layer, a p-type InGaAsP upper grating layer, a p-type InP filling layer, a p-type InP cap layer, and a P-type heavily doped InGaAs contact layer.

In the solution of this embodiment, the laser is divided into a first mode selection area 100 and a second mode selection area 200 in the direction of the laser cavity length. Optionally, the two areas can be separated by an electrical isolation groove. The first mode selection area 100 and the second mode selection area 200 respectively make distributed feedback grating structures in the lower grating layer 08 and the upper grating layer 10.

In summary, as a specific solution of the present invention, the laser can be a buried heterojunction waveguide or a ridge waveguide.

The five double-grating DFB samples prepared according to the structure of Example 1 of the present invention were subjected to relevant anti-reflection threshold tests, and the anti-reflection threshold tests were performed on five conventional DFB lasers. The test results are compared as follows:

Table 1

Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Mean Traditional DFB -20.5dB -20.1dB -19.8dB -21.0dB -21.4dB -20.5dB Dual Grating DFB -15.4dB -14.8dB -16dB -15.8dB -15.0dB -15.4dB

Table 1 shows the anti-reflection thresholds of the traditional DFB laser and the dual-grating DFB laser proposed in this paper. The numbers in the table represent the ratio of the laser return light to the output light power. The larger the number, the stronger the anti-reflection ability of the laser. It should be noted that, except for the different grating layers, the number of quantum wells, the thickness of each epitaxial layer and the cavity length of the two types of lasers are set the same.

It can be clearly observed from Table 1 that, compared with a traditional DFB laser having only one grating layer, the dual-grating DFB laser proposed in the present application can significantly improve the anti-reflection capability of the laser.

The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims (10)

1. The high-power anti-reflection semiconductor laser is characterized by sequentially comprising an N-face metal layer (01), a substrate layer (02), a buffer layer (03), a lower limiting layer (04), a multiple quantum well layer (05), an upper limiting layer (06), a lower spacing layer (07), a lower grating layer (08), an upper spacing layer (09), an upper grating layer (10), a filling layer (11), a cover layer (12), a contact layer (13), a passivation layer (14) and a P-face metal layer (15) from bottom to top;

The laser is divided into a first mode selection area (100) and a second mode selection area (200) along the length direction of the laser cavity; the first mode selection area (100) and the second mode selection area (200) respectively manufacture distributed feedback grating structures on the lower grating layer (08) and the upper grating layer (10).

2. A high power anti-reflective semiconductor laser according to claim 1, characterized in that the vertical projection directions of the distributed feedback grating structure on the lower grating layer (08) and the distributed feedback grating structure on the upper grating layer (10) do not overlap.

3. A high power anti-reflective semiconductor laser according to claim 1, characterized in that the thickness, composition and grating period of the lower grating layer (08) and the upper grating layer (10) are the same or different.

4. A high power anti-reflective semiconductor laser according to claim 1, characterized in that the thickness of the lower (08) and upper (10) grating layers is 10-100 nm.

5. A high power anti-reflective semiconductor laser according to claim 1, characterized in that the doping concentration of the distributed feedback grating structure of the lower grating layer (08) and the upper grating layer (10) is 4e ¹⁷/cm³～1e¹⁸/cm³, and the material luminescence wavelength is 1.0 μm-1.3 μm.

6. A high power anti-reflective semiconductor laser according to claim 1, wherein the laser has a cavity length of 200 μm to 5000 μm.

7. The high-power anti-reflection semiconductor laser according to claim 1, wherein the electrode patterns of the P-side metal layer (15) of the first mode selection region (100) and the second mode selection region (200) are integrated, or an electrical isolation trench is formed by etching the cap layer (12) and the contact layer (13), and the P-side metal layer (15) is isolated by pattern separation.

8. A high power anti-reflective semiconductor laser according to claim 1, characterized in that the high power anti-reflective semiconductor laser is a buried heterojunction waveguide or a ridge waveguide.

9. A high power anti-reflective semiconductor laser according to claim 1, characterized in that the number of pairs of multi-quantum well layers (05) is 2-10.

10. A high power anti-reflective semiconductor laser according to any of claims 1 to 9, characterized in that the N-side metal layer (01) is an AuGeNi/Au alloy layer, the substrate layer (02) is an N-type InP substrate, the buffer layer (03) is Si-doped N-type InP, the lower confinement layer (04) is an InGaAsP or InGaAlAs layer, the multiple quantum well layer (05) is InGaAsP or InGaAlAs, the upper confinement layer (06) is InGaAsP or InGaAlAs, the lower spacer layer (07) is InP, the lower grating layer (08) is InGaAsP, the upper spacer layer (09) is InP, the upper grating layer (10) is InGaAsP, the filler layer (11) is InP, the cap layer (12) is Zn-doped InP, the contact layer (13) is Zn-doped InGaAs, the passivation layer (14) is SiO (2) or SiNx, and the P-side metal layer (15) is Ti/Pt/Au alloy.