A distributed feedback laser and a method for manufacturing the same

Abstract

The present invention discloses a distributed feedback laser and a manufacturing method thereof, the method comprising: growing a buffer layer on a substrate; manufacturing a plurality of strip dielectric mask patterns with equal spacing and the same width on the buffer layer; growing active materials on the buffer layer other than each of the strip dielectric mask patterns by MOCVD to form an active layer; removing all the strip dielectric mask patterns on the buffer layer; sequentially growing a spacer layer, an etching stop layer, a cladding layer and a contact layer on the active layer and the buffer layer after the strip dielectric mask patterns are removed; and manufacturing a ridge waveguide on the cladding layer. The present invention forms a periodic grating structure in the active material through the dielectric mask pattern, and can be manufactured by low-cost contact lithography technology to reduce the manufacturing cost of single longitudinal mode semiconductor lasers, which is helpful to promote the large-scale application of single longitudinal mode semiconductor lasers.

Description

Technical Field

[0001] The invention relates to the technical field of distributed feedback integrated laser manufacturing, and in particular to a distributed feedback laser and a manufacturing method thereof. Background Art

[0002] The introduction of distributed feedback grating structure is an important means to obtain single-mode semiconductor lasers, which are called distributed feedback (DFB) lasers. Due to its excellent single-mode characteristics and narrow bandwidth, DFB lasers are widely used in optical communications, laser radar, spectral analysis, medical imaging diagnosis and other technical fields.

[0003] In order to manufacture a DFB laser, a periodic grating structure needs to be formed in the chip of the semiconductor laser. The period of the grating is usually tens to hundreds of nanometers, which matches the working wavelength of the laser. At present, the commonly used grating manufacturing processes mainly include electron beam exposure, holographic exposure and material etching. Electron beam exposure uses an electron beam to directly etch the grating pattern, which has high precision and can produce fine grating structures; holographic exposure generates gratings on photosensitive materials by laser interference, which is usually suitable for larger-scale grating production; material etching refers to the use of plasma etching technology to process the material after the grating is made to obtain the desired grating shape. However, these methods require the use of grating pattern generation equipment such as electron beam exposure or holographic exposure, as well as material etching equipment such as ICP or RIE. These equipment are expensive and cumbersome to operate, and the precision requirements of the manufacturing process are also very high, which greatly increases the process complexity of laser manufacturing, making single longitudinal mode semiconductor lasers have a high manufacturing cost, limiting their large-scale application.

[0004] Therefore, there is an urgent need to provide a distributed feedback laser and a method for manufacturing the same, which can utilize ordinary contact lithography technology to obtain a semiconductor laser operating in a single longitudinal mode, so as to reduce the manufacturing cost of the single longitudinal mode semiconductor laser and promote the large-scale application of the single longitudinal mode semiconductor laser. Summary of the invention

[0005] In view of this, the present invention provides a distributed feedback laser and a manufacturing method thereof, so as to solve the technical problem that the application scope of single longitudinal mode semiconductor laser is limited due to the complex manufacturing process and high manufacturing cost of the existing feedback laser.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides a method for manufacturing a distributed feedback laser, comprising:

[0008] growing a buffer layer on the substrate;

[0009] Making a plurality of strip-shaped dielectric mask patterns with equal spacing and the same width on the buffer layer;

[0010] Growing active material on the buffer layer outside each of the strip-shaped dielectric mask patterns by MOCVD to form an active layer;

[0011] removing all strip-shaped dielectric mask patterns on the buffer layer;

[0012] Sequentially stacking and growing a spacer layer, an etching stop layer, a cladding layer and a contact layer on the active layer and the buffer layer after the strip-shaped dielectric mask pattern is removed;

[0013] A ridge waveguide is fabricated on the cladding.

[0014] Furthermore, the material of the substrate is one of GaAs, InP, GaN and GaSb.

[0015] Furthermore, the manufacturing area of ​​the dielectric mask pattern is the entire length range of the laser, or a partial area of ​​the total length range of the laser.

[0016] Furthermore, the active material grows only in the buffer layer between the strip-shaped dielectric mask patterns, and the grown active layer is strip-shaped and its direction is perpendicular to the ridge waveguide.

[0017] Furthermore, the material of the active layer is bulk material or quantum well material.

[0018] Furthermore, the material of the strip-shaped dielectric mask pattern is silicon oxide or silicon nitride.

[0019] Furthermore, the direction of the ridge waveguide is perpendicular to the direction of the dielectric mask pattern.

[0020] Furthermore, the ridge waveguide corrosion or etching stops on the corrosion stop layer.

[0021] Furthermore, the material of the buffer layer is InP, the material of the spacer layer is InP, the material of the etching layer is InGaAsP, and the material of the cladding layer and the contact layer is InGaAs.

[0022] On the other hand, the present invention also provides a distributed feedback laser, which is manufactured by any of the above-mentioned distributed feedback laser manufacturing methods, comprising: a substrate, a buffer layer is arranged on the substrate, the buffer layer has a plurality of active material regions with equal spacing and the same width, the plurality of active material regions form an active layer, a spacer layer, an etching stop layer, a cladding and a contact layer are sequentially stacked on the active layer and the buffer layer, and a ridge waveguide is arranged on the cladding.

[0023] Compared with the prior art, the method for manufacturing a distributed feedback laser provided by the present invention utilizes a mask pattern to accurately control the growth area of ​​an active material, and adopts ordinary contact lithography technology to manufacture a dielectric mask pattern before the growth of the active material to obtain single longitudinal mode operation, which can effectively reduce the process complexity of manufacturing a single-mode semiconductor laser, thereby reducing the manufacturing cost of a single longitudinal mode semiconductor laser, and contributing to the large-scale promotion and application of distributed feedback lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic flow chart of a method for manufacturing a distributed feedback laser provided by the present invention;

[0025] Figure 2 A schematic diagram of the structure of a substrate, a buffer layer and a strip dielectric mask provided by the present invention;

[0026] Figure 3 A top view of the strip dielectric mask provided by the present invention;

[0027] Figure 4 A schematic structural diagram of the active layer provided by the present invention;

[0028] Figure 5 A schematic diagram of the overall structure of the distributed feedback laser provided by the present invention;

[0029] In the figure, 10 - substrate, 20 - buffer layer, 30 - active layer, 40 - spacer layer, 50 - etching stop layer, 60 - cladding layer, 70 - contact layer, 80 - ridge waveguide. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0031] See also Figure 1 The present invention provides a method for manufacturing a distributed feedback laser, comprising the following steps:

[0032] Step S101: growing a buffer layer on a substrate;

[0033] Step S102: making a plurality of strip-shaped dielectric mask patterns with equal spacing and the same width on the buffer layer;

[0034] Step S103: growing active material on the buffer layer outside each of the strip-shaped dielectric mask patterns by using MOCVD to form an active layer;

[0035] Step S104: removing all strip-shaped dielectric mask patterns on the buffer layer;

[0036] Step S105: sequentially stacking and growing a spacer layer, an etching stop layer, a cladding layer and a contact layer on the active layer and the buffer layer after the strip dielectric mask pattern is removed;

[0037] Step S106: fabricating a ridge waveguide on the cladding.

[0038] The method of this embodiment can effectively reduce the process complexity of single-mode semiconductor laser manufacturing and reduce the manufacturing cost of semiconductor lasers by using ordinary contact lithography technology to produce a dielectric mask pattern before the active material grows to obtain single longitudinal mode operation, and has extremely strong practical value.

[0039] Combine the following Figure 2-Figure 5 , taking the InP-based material system as an example, the manufacturing method of the above-mentioned distributed feedback laser is described in detail. The manufacturing process includes the following steps:

[0040] Step 1: growing an InP buffer layer 20 on an InP substrate 10, with an overall length range of L, such as Figure 2 shown.

[0041] Step 2: Make a stripe dielectric mask pattern m on the InP buffer layer 20, such as Figure 3 As shown, Figure 3 The medium is a top view of a mask pattern m, the mask pattern is in the shape of strips, the number of the strip patterns is at least 1, the width thereof is t, the spacing is w, and the spacing between the strips is equal.

[0042] Step 3: Using MOCVD to grow active materials on the InP buffer layer 20 with the dielectric mask pattern, the active materials form the active layer 30, such as Figure 4 During the growth process, the active material cannot grow on the dielectric mask pattern m, but can only grow on the InP buffer layer 20 between the two strip dielectric mask patterns, forming a Figure 4 The active layer 30 is shown in a stripe shape.

[0043] Step 4: Remove the dielectric mask pattern m.

[0044] Step 5: Growing an InP spacer layer 40, an InGaAsP etching stop layer 50, an InP cladding layer 60 and an InGaAs contact layer 70 on the active layer 30 and the InP buffer layer 20 after removing the dielectric mask pattern, as shown in FIG. Figure 5 shown.

[0045] Step 6: Fabricate the laser ridge waveguide 80, whose etching or etch stops on the etching stop layer 50, such as Figure 5 The ridge waveguide direction is perpendicular to the mask strip direction and the strip active layer 30 direction, or has an angle greater than 70 degrees.

[0046] Through the above-mentioned manufacturing method, the InP material is used between the strip active materials in the device, and its refractive index is smaller than that of the active material, forming a grating structure with periodic refractive index variation, which modulates the light transmitted along the ridge waveguide, and a single longitudinal mode luminescent semiconductor laser can be obtained.

[0047] The refractive index difference between the active material and the InP material is large, so a larger grating coupling coefficient can be obtained. When the grating is a high-order grating structure, the mask strip width and period are both greater than 1 micron, so it can be made using ordinary contact lithography technology, with low production cost and good stability.

[0048] In addition, when the distributed feedback laser is working, only the strip active material provides optical gain, and the InP material in the middle of the strip active material has no gain. The gain coupling effect is introduced in the laser, which is beneficial to improve the performance of the laser, especially in terms of wavelength selectivity, temperature stability, spectral characteristics and output power. In a distributed feedback laser, the gain coupling effect helps match the gain spectrum of the laser with the wavelength of the feedback grating, making the feedback mechanism more efficient. This means that a specific wavelength will obtain more gain in the feedback grating, thereby increasing the output power of the laser at that wavelength. At the same time, by optimizing the gain coupling, the DFB laser can operate stably at higher temperatures, reducing the negative impact of temperature on gain and feedback, thereby improving overall performance. In terms of output power, gain coupling makes the light more concentrated in the gain region of the laser cavity, thereby improving the efficiency of the laser. In this way, as much input current as possible can be converted into effective light output, thereby increasing the overall output power.

[0049] It should be noted that the dielectric mask pattern can be distributed within the entire device length range L, or it can only occupy a part of the device length. When the mask pattern covers the entire length of the device, the distributed feedback structure (DFB structure) of the laser will act evenly on the entire laser length. This design can ensure that the laser produces stable single longitudinal mode output when working, optimize the spectral characteristics of the laser, and ensure that the light propagation mode of the waveguide is uniformly adjusted, especially in applications with long-distance transmission and high-precision requirements, to ensure higher performance. In some cases, the mask pattern is only designed to cover a part of the device (such as the front section or the back section). This design can make the laser produce a strong feedback effect in a local area, thereby realizing specific functions in this area. The local distributed feedback mask design can adjust the modulation characteristics of the laser, such as adjusting the output power, spectral width or suppression of a specific mode in a certain wavelength range, and has high adjustability.

[0050] As a preferred embodiment, in addition to the InP substrate, this type of laser can also be made of substrate materials such as GaAs, GaN or GaSb.

[0051] As a preferred embodiment, the material of the dielectric mask pattern is silicon oxide or silicon nitride.

[0052] As a preferred embodiment, the active material may be a bulk material or a quantum well material, such as an InGaAsP material or an InGaAlAs material. In addition, the thickness of the strip active material grown in the middle area of ​​the mask is greater than that in the area without the mask.

[0053] Different types of active materials have their own unique advantages and applicable scenarios. Among them, bulk materials are suitable for high-power lasers, simple and with strong gain, but with low efficiency and poor temperature stability. Quantum well materials have the advantages of high efficiency and low threshold current, and are suitable for applications requiring high efficiency and low current, especially lasers requiring low power consumption and temperature stability. InGaAsP is suitable for fiber-optic communications and long-wavelength applications, with good electro-optical conversion efficiency and compatibility with optical fibers. InGaAlAs is suitable for wide bands, especially medium and long wavelength lasers, and has excellent efficiency and thermal stability.

[0054] The embodiment of the present invention further provides a distributed feedback laser, which is manufactured by any of the above-mentioned distributed feedback laser manufacturing methods, such as Figure 5 As shown, the distributed feedback laser includes: a substrate 10, a buffer layer 20 is arranged on the substrate 10, and the buffer layer 20 has a plurality of active material regions with equal spacing and the same width, and the plurality of active material regions form an active layer 30, and a spacer layer 40, an etching stop layer 50, a cladding 60 and a contact layer 70 are sequentially stacked on the active layer 30 and the buffer layer 20, and a ridge waveguide 80 is arranged on the cladding 60.

[0055] In summary, the distributed feedback laser and its manufacturing method provided by the present invention have the advantages that by using a dielectric mask pattern to form a periodic grating structure in the active material, a single longitudinal mode semiconductor laser can be manufactured using low-cost contact lithography technology. Compared with the existing technology of manufacturing DFB lasers by electron beam exposure, holographic exposure and other methods, the manufacturing cost is greatly reduced, which helps to promote the large-scale application of single longitudinal mode semiconductor lasers.

[0056] 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 changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for manufacturing a distributed feedback laser, characterized in that: include: growing a buffer layer on the substrate; Making a plurality of strip-shaped dielectric mask patterns with equal spacing and the same width on the buffer layer; Growing active material on the buffer layer outside each of the strip-shaped dielectric mask patterns by MOCVD to form an active layer; removing all strip-shaped dielectric mask patterns on the buffer layer; Sequentially stacking and growing a spacer layer, an etching stop layer, a cladding layer and a contact layer on the active layer and the buffer layer after the strip-shaped dielectric mask pattern is removed; A ridge waveguide is fabricated on the cladding.

2. The method for manufacturing a distributed feedback laser according to claim 1, characterized in that: The material of the substrate is one of GaAs, InP, GaN and GaSb.

3. The method for manufacturing a distributed feedback laser according to claim 1, characterized in that: The manufacturing area of ​​the dielectric mask pattern is the entire length range of the laser, or a partial area of ​​the total length range of the laser.

4. The method for manufacturing a distributed feedback laser according to claim 1, characterized in that: The active material grows only in the buffer layer between the strip-shaped medium mask patterns, and the grown active layer is strip-shaped and its direction is perpendicular to the ridge waveguide.

5. The method for manufacturing a distributed feedback laser according to claim 1, characterized in that: The material of the active layer is bulk material or quantum well material.

6. The method for manufacturing a distributed feedback laser according to claim 1, characterized in that: The material of the strip-shaped dielectric mask pattern is silicon oxide or silicon nitride.

7. The method for manufacturing a distributed feedback laser according to claim 1, characterized in that: The direction of the ridge waveguide is perpendicular to the direction of the dielectric mask pattern.

8. The method for manufacturing a distributed feedback laser according to claim 1, characterized in that: The ridge waveguide erosion or etching stops on the etch stop layer.

9. The method for manufacturing a distributed feedback laser according to claim 1, characterized in that: The material of the buffer layer is InP, the material of the spacer layer is InP, the material of the corrosion layer is InGaAsP, and the material of the cladding layer and the contact layer is InGaAs.

10. A distributed feedback laser, characterized in that: The distributed feedback laser is manufactured by the manufacturing method according to any one of claims 1 to 9, comprising: a substrate, a buffer layer is arranged on the substrate, the buffer layer has a plurality of active material regions with equal spacing and the same width, the plurality of active material regions form an active layer, a spacer layer, an etching stop layer, a cladding and a contact layer are sequentially stacked on the active layer and the buffer layer, and a ridge waveguide is arranged on the cladding.

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