CN107230931B - Distributed feedback semiconductor laser chip, preparation method thereof and optical module - Google Patents

Abstract

The invention discloses a distributed feedback semiconductor laser chip, a preparation method thereof, and an optical module. Specifically, two or more active regions with different widths are designed in one laser chip, and the The grating end faces formed by dissociation have the same phase. Since the effective refractive index Neff of the laser is determined by the active region material, width, thickness and other factors, under the premise that other factors in the chip are the same, the effective refractive index Neff corresponding to the chip units with different active region widths is also different. At the same time, the output wavelength of the DFB laser is affected by Neff, so the change of the width of the active region in the laser chip will eventually cause the change of the output wavelength of each active region. Further, two lasers with different wavelengths have different edge mode suppression ratios under the same grating end face phase. Therefore, the edge mode suppression ratio performance can be selected from the chip units corresponding to each active area of a chip. The unit is packaged to improve the chip yield.

Description

Distributed feedback semiconductor laser chip and preparation method thereof, and optical module

technical field

The invention relates to the technical field of optical communication, in particular to a distributed feedback semiconductor laser chip, a preparation method thereof, and an optical module.

Background technique

Optical transceiver module, referred to as optical module, is a standard module in optical fiber communication. A standard optical module usually includes devices such as optical transmitter, optical receiver, microprocessor and laser driver. Among them, the laser is the key component in the optical transmitter. Due to the requirements of low loss and low dispersion in optical fiber transmission, indium phosphide-based semiconductor lasers with wavelengths of 1.3 to 1.5 microns have become the mainstream products used in optical modules. Among them, the distributed feedback laser (Distributed Feedback Brag, DFB) is more widely used because of the advantages of good single longitudinal mode performance and longer transmission distance.

When Bell Labs proposed the concept of distributed feedback gratings in 1972, the gratings in DBF lasers were divided into two types, namely gain-coupled gratings and refractive index coupled gratings. Since the gain-coupled grating needs to directly etch the active region, various defects will be introduced to affect the reliability and stability of the device. Therefore, at present, refractive index-type coupled gratings are mostly designed in lasers. In DBF lasers with refractive index coupled gratings, in order to improve the performance of the gratings, various complex grating structures are usually designed, such as multi-phase-shift gratings, periodic modulation gratings, etc. It is not suitable for mass production, so most of them still use uniform grating structures. Figure 1 is a schematic diagram of the basic structure of a typical uniform grating DFB semiconductor laser. As shown in Fig. 1, the DFB semiconductor laser includes a built-in uniform grating 10 arranged along the direction of its ridges. The grating is used to form a resonant cavity, and the working wavelength can be selected to realize dynamic single longitudinal mode operation and obtain stable single wavelength laser. In the related art, the above-mentioned uniform grating is usually produced by holographic interference technology. Specifically, the light emitted by the laser is divided into two light waves to form interference on the wafer, and the period of the grating is adjusted by adjusting the angle of the incident light. After other chip preparation processes are completed on the wafer, the chips on the wafer are divided into independent DFB semiconductor laser chips by means of chip dicing technology.

However, in the above-mentioned DFB semiconductor laser, one period of the grating is usually small (about 200 μm), and the error during chip cutting is 5 to 20 μm, so the last period of the grating (the one closest to the laser cavity surface) is caused. ) cutting position is uncontrollable, resulting in randomness of the phase at the end of the grating. However, the gain difference between the two modes in the laser is also affected by the phase at the end of the grating. Therefore, the random change of the phase at the end of the grating will cause the instability of the gain difference between the two modes in the laser, which will ultimately affect the single-longitudinal mode yield of the DFB semiconductor laser.

SUMMARY OF THE INVENTION

The invention provides a distributed feedback semiconductor laser chip, a preparation method and an optical module to solve the problem of low single longitudinal mode yield of the DFB semiconductor laser caused by the uncontrollable phase of the grating end in the DFB semiconductor laser chip.

According to a first aspect of the embodiments of the present invention, the present invention provides a distributed feedback semiconductor laser chip, and the distributed feedback semiconductor laser chip includes:

substrate;

a first active region and a second active region disposed on the substrate, wherein the widths of the first active region and the second active region are different; and,

a first grating disposed on the first active region, the light emitted by the first active region undergoes Bragg reflection at the first grating;

a second grating disposed on the second active region, the light emitted by the second active region undergoes Bragg reflection at the second grating;

The grating end faces formed by dissociation of the first grating and the second grating have the same phase.

According to a second aspect of the embodiments of the present invention, there is provided a method for fabricating a distributed feedback semiconductor laser chip, the method comprising:

forming an active region on the substrate;

preparing a grating on the active region;

preparing a periodically arranged active area stripe structure on the active area formed with the grating, wherein each chip period includes a first active area and a second active area with different widths;

preparing a reverse PN junction, a P-type confinement layer, an ohmic contact layer and a metal electrode on the wafer formed with the active region stripe structure and the grating to obtain a wafer with a plurality of distributed feedback semiconductor laser chips;

The wafer with a plurality of distributed feedback semiconductor laser chips is subjected to cavity end face coating and chip dissociation to obtain a plurality of independent distributed feedback semiconductor laser chips.

According to a third aspect of the embodiments of the present invention, another method for fabricating a distributed feedback semiconductor laser chip is also provided, the method comprising:

fabricating a uniform grating on a P-waveguide layer in a wafer formed with quantum well active regions;

growing a P-type confinement layer and an ohmic contact layer on the wafer formed with the grating;

preparing periodically arranged ridge waveguides on the wafer formed with the ohmic contact layer, wherein each chip cycle includes at least two ridge waveguides with different widths;

preparing metal electrodes on the wafer formed with the ridge waveguide structure to obtain a wafer with a plurality of distributed feedback semiconductor laser chips;

The wafer with a plurality of distributed feedback semiconductor laser chips is subjected to cavity end face coating and chip dissociation to obtain a plurality of independent distributed feedback semiconductor laser chips.

According to a fourth aspect of the embodiments of the present invention, an optical module is also provided, the optical module includes an optical transmitter, and the optical transmitter is provided with the distributed feedback semiconductor laser chip provided in the first aspect of the embodiments of the present invention.

It can be seen from the above technical methods that in a distributed feedback semiconductor laser chip, a preparation method thereof, and an optical module provided by the embodiments of the present invention, two or more active regions with different widths are designed in one laser chip, and each has a different width. The grating on the source region has the same phase of the grating end faces formed by dissociation. Since the effective refractive index Neff of the laser is determined by the active region material, width, thickness and other factors, under the condition that the active region material, thickness and other factors of the laser chip are fixed, the effective refractive index Neff varies with the active region width. changes, and further the effective refractive index Neff corresponding to the chip units with different widths of the active regions is also different. At the same time, the output wavelength of the DFB laser has the following relationship with the grating period and the effective refractive index: λ=2*Λ*Neff, where Λ is the grating period. It can be seen from the above analysis that the change of the width of the active region of the laser chip will eventually cause the change of its wavelength. Further, two lasers with different wavelengths have different edge-mode rejection ratios under the same grating end-face phase condition. Therefore, two or more semiconductor laser chip units are formed on the size of a single semiconductor laser chip. When selecting a laser chip, a chip unit with better edge-to-edge suppression ratio performance can be selected from the chips and packaged as an effective chip, and then The yield of the DFB laser chip can be greatly improved, and the production cost can be reduced.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.

Description of drawings

In order to illustrate the technical solutions of the present invention more clearly, the accompanying drawings that need to be used in the embodiments will be briefly introduced below. Other drawings can also be obtained from these drawings.

Figure 1 is a schematic diagram of the basic structure of a typical uniform grating DFB semiconductor laser;

2 is a schematic diagram of a surface structure of a DFB semiconductor laser chip in the prior art;

FIG. 3 is a schematic diagram of the end phase of the grating in the DFB semiconductor laser chip of FIG. 2;

4 is a schematic diagram of a surface structure of a DFB semiconductor laser chip provided by an embodiment of the present invention;

5 is a schematic cross-sectional structure diagram of the DFB semiconductor laser chip in FIG. 4;

6 is a schematic diagram of a grating structure in the DFB semiconductor laser chip in FIG. 4;

7 is a schematic diagram of the simulation results of the side mode suppression ratio of the DFB semiconductor laser chip in FIG. 4 under different grating end phases;

8 is a cross-sectional view of preparing active region mesas with different widths on a wafer formed with quantum well active regions according to an embodiment of the present invention;

FIG. 9 is a schematic cross-sectional structure diagram of a reverse PN junction, a P-type confinement layer and an ohmic contact layer grown on the wafer in FIG. 8 .

Detailed ways

Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. Where the following description refers to the drawings, the same numerals in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the illustrative examples below are not intended to represent all implementations consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with some aspects of the invention as recited in the appended claims.

The refractive index grating refers to the periodic change of the real part of the refractive index along the length of the laser cavity, that is, the refractive index, which forms a distributed feedback mechanism of forward light and backward light fields. A typical refractive index coupling structure is a grating etched on the transparent waveguide layer adjacent to the active region. The content studied in the examples of the present invention is mainly aimed at DFB semiconductor lasers with refractive index type uniform gratings.

FIG. 2 is a schematic diagram of the surface structure of a DFB semiconductor laser chip in the prior art. As shown in FIG. 2 , the laser chip mainly includes an active area 1 of the laser chip (the top of the active area is covered with a metal electrode), a metal pad 2 connected to the metal electrode above the active area, and two light sources at the front and back. The cavity surface (shown by the two arrows in the figure), the two light-emitting cavity surfaces of the laser chip have different coatings, and the rear light-emitting cavity surface is a high-reflection coating (usually higher than 95%, called "high-reflection film"), The front light-emitting surface cavity is a low-reflection film with a reflectivity of about 0, which is used to break the balance of the two modes in the laser chip. FIG. 3 is a schematic diagram of the end phase of the grating in the DFB semiconductor laser chip in FIG. 2 . As shown in FIG. 3, a uniform grating 3 is disposed above the active region 1 to provide a wavelength selection mechanism. Due to the uncontrollable cleavage or cutting position of the grating end, the phase of the grating end is uncontrollable, where the phase of the grating end can be expressed as: e ^jΔ/Λ , Λ is the grating period, and Δ is the dissociation position. Further, the reflection of the end cavity surface depends on the phase of the grating, and the reflection coefficient is multiplied by the phase of the grating. Due to the randomness of the phase of the end of the grating, the end surface reflection of the laser chip changes with the phase, which in turn causes the gain difference of the two modes to be unstable, SMSR ( Side-Mode Suppression Ratio) is also unstable, resulting in the problem of low single-mode yield of laser chips (theoretical single-mode yield is between 40-50%). In view of this problem, the example of the present invention optimizes the design of the active region in the laser chip, so as to improve the laser yield and reduce the manufacturing cost of this type of laser. The DFB laser chip and the preparation method provided by the example of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 4 is a schematic diagram of a surface structure of a DFB semiconductor laser chip provided by an embodiment of the present invention. FIG. 5 is a schematic cross-sectional structure diagram of the DFB semiconductor laser chip in FIG. 4 . As shown in Figures 4 and 5, the laser chip includes a substrate 50, a first active region 15 and a second active region 25 disposed on the substrate; further, as shown in Figure 6, in the DFB semiconductor laser chip In the schematic diagram of the grating structure shown in FIG. 2 , a first grating 16 is provided on the first active region 15 , and a second grating 26 is provided on the second active region 25 . Wherein, an isolation trench 30 is provided between the first active region 15 and the second active region 25, and the isolation trench 30 extends downward from the surface of the distributed feedback semiconductor laser chip unit to the substrate 50 thereof, to reduce parasitic capacitance.

According to the distribution characteristics of the above-mentioned active regions, the DFB semiconductor laser chip is divided into two chip units in this embodiment, which are respectively referred to as the first DFB semiconductor laser chip unit 10 and the second DFB semiconductor laser chip unit 20, wherein the first DFB semiconductor laser chip unit 20 The active area 15 is located in the first chip unit, and the second active area 25 is located in the second chip unit. Since the first DFB semiconductor laser chip unit 10 and the second DFB semiconductor laser chip unit 20 are fabricated by the same epitaxy and chip process, the number of layers of chip materials, the arrangement order, thickness and materials used in the two layers are the same.

The structure of the chip will be described below by taking the second chip unit as an example. As shown in FIG. 5 , the chip unit includes a substrate 50 , an N-type confinement layer 28 , an active region 25 , a reverse PN junction 27 (P-type InP confinement layer and N-type InP confinement layer), P-type confinement layer 24 , P-type ohmic contact layer 23 , P-side metal electrode 22 and N-side metal electrode 40 .

The material constituting the substrate 50 may be a semiconductor material having good crystal quality and good lattice matching with the material grown thereon. The embodiment of the present invention takes a long-wavelength laser as an example. In this case, the material of the substrate 50 may be N-type InP. Of course, the material of the substrate 50 may also be other semiconductor materials. For example, for a GaAs laser, the material of the substrate 50 The material can be N-type GaAs. In addition, the surface of the substrate 50 should be flat and defect-free to facilitate the growth of layers thereon.

In the embodiment of the present invention, the material of the active region 25 may be InGaAsP, and in addition, the active region 25 may also be a stack composed of InGaAlAs and InGaAs. In order to achieve better lattice matching between the active region 25 and the substrate 50 , a buffer layer may also be formed between the substrate 50 and the active region 25 . An N-type confinement layer 28 and a P-type confinement layer 24 may be formed on both sides of the active region 25 , and the confinement layers may be used to confine the light field around the active region 25 to the greatest extent.

In addition, reverse PN junctions 27 are formed on both sides of the buried waveguide formed by the active region 25 and part of the N-type confinement layer 28 for confining current to pass through the active region 25 . A P-type ohmic contact layer 23 for forming an ohmic contact may be formed over the P-type confinement layer 24 .

Further, since the first grating 16 and the second grating 26 disposed above the active region are prepared by the same grating preparation process, the type, position, period and total grating length of the two gratings are the same; and , the cleavage position of the end grating end obtained by the dissociation of the two at the same time is also the same, that is, the phase of the grating end face of the two is the same. Similarly, the two chip units are coated on the cavity surfaces at the same time, so the reflectivity of the two light-emitting cavity surfaces at the front and the rear of the two chip units are the same.

Therefore, according to the above analysis, the only difference between the two chip units is that the widths of the active regions are different. The width of the active region 15 of the first DFB semiconductor laser chip unit 10 is Wa, and the width of the active region 25 of the second DFB semiconductor laser chip unit 20 is Wb. In the embodiment of the present invention, Wb is designed to be larger than Wa.

Since the effective refractive index Neff of the laser is determined by the active region material, width, thickness and other factors, under the condition that the epitaxial layer structure and optical waveguide of the above two chip units are the same, the active region material, thickness, etc. are all The same, so the effective refractive index Neff of the two chip units is only affected by the width of its active area, even if the effective refractive index Neff of the two is different because only the width of the active area is an influencing factor, therefore, the above active area The effective refractive index Neff of the two chip units with different widths is also different. In addition, the output wavelength of the DFB laser has the following relationship with the grating period and the effective refractive index: λ=2*Λ*Neff, where Λ is the grating period. Therefore, the change of the width of the active regions of the above two chip units leads to the change of the effective refractive index thereof, and finally causes the change of the output wavelength thereof.

Further, in the DFB laser, the light emitted from the active region enters the grating for Bragg reflection, that is, relying on the built-in Bragg grating, which is a distributed feedback that is strongly related to the wavelength, the longitudinal mode satisfying the resonant phase condition will have After the different losses are superimposed with the parabolic gain spectrum, the longitudinal mode with the largest net increase achieves lasing. Therefore, two lasers with different output wavelengths have different edge-mode suppression ratios under the same grating end-face phase conditions and cavity surface reflectivity, and the single-mode yields corresponding to the two chip units are different.

Therefore, when packaging the above-mentioned laser chips, the chip units with better edge-mode suppression ratio performance can be selected from each chip unit as an effective chip for packaging, so as to prevent the single-mode suppression ratio of the chip from being inconsistent due to the phase deviation of the grating end face. In the case of scrapping according to the preset requirements, the yield of the DFB laser chip can be greatly improved and the production cost can be reduced.

In order to ensure the overall working performance of the laser, the embodiment of the present invention further limits the width of the active region in each chip unit in the chip. Specifically, the upper limit values of the widths Wa and Wb of the active regions of the first DFB semiconductor laser chip unit 10 and the second DFB semiconductor laser chip unit 20 are set according to the requirement that the corresponding feedback semiconductor laser chip units work in the fundamental transverse mode. Certainly. Since the width of the active region to ensure the operation of the fundamental transverse mode is related to the design of the quantum well, such as wavelength, quantum well material, number of wells, thickness of each layer and other factors, therefore, in practical applications, it is necessary to design according to the actual quantum well , such as the widest is 2um. Further, the lower limit values of the active area widths Wa and Wb of the above-mentioned first DFB semiconductor laser chip unit 10 and the second DFB semiconductor laser chip unit 20 are based on the slope efficiency of the corresponding feedback semiconductor laser chip unit. Meet the preset efficiency value setting. Since the output power, slope efficiency, series resistance and reliability of the laser will deteriorate with the narrowing of the active region, the slope efficiency is a key physical quantity to measure the output characteristics of the laser, which is related to the output power and pump power of the laser. The related physical quantities, therefore, the embodiments of the present invention utilize the slope efficiency to define the active region width value.

In order to make the edge mode suppression ratio of each DFB semiconductor laser chip unit in the DFB semiconductor laser chip have a large difference, so that the chip unit with better SMSR can be successfully found for packaging when selecting the die, the example of the present invention will distribute feedback The difference between the widths of the active regions in the semiconductor laser chip is designed such that the difference between the output wavelengths of the first active region 15 and the output wavelengths of the first active region 25 is greater than or equal to 1 nm.

For example, under the premise that the DFB semiconductor laser chip provided by the embodiment of the present invention has a buried waveguide structure, the output wavelength is in the 1510 nm band, and the grating period is 200 nm, the width Wa of the first active region is calculated to be narrower than the width Wb of the second active region 0.2um, the output wavelength of the two can differ by more than 1nm.

Of course, the above-mentioned difference in the width of the active region can also be other data such as 0.3um, 0.5um, etc., which depends on whether the widest waveguide approaches the upper limit of the allowable waveguide width and whether the narrowest waveguide approaches the lower limit of the allowable waveguide width. Decide. Further, in order to provide sufficient control margin for process manufacturing, the widest and narrowest active region widths should be as far away from the upper or lower limit as possible. For example, if the acceptable range of the active region width is 1.2-1.7um, then the two The optimum range of the width of the active region is 1.35um-1.55um, that is, in the middle of the allowable range of 1.2-1.7um. In addition, the design of the laser chip provided in this embodiment is not only applicable to the 1510 nm wavelength band, but also applicable to the wavelength range of 850-1550 nm.

It should be noted that, in the embodiment of the present invention, in order to reduce the laser reverse leakage current and parasitic capacitance between the optical chip units in the chip, isolation trenches are provided between adjacent chip units. In specific applications, the groove may not be designed, or the groove may be designed to other depths.

Further, since only one of the above two distributed feedback semiconductor laser chip units is selected as an effective chip for wire bonding during packaging, in order to facilitate the testing of the chip and the work of packaging wire bonding, the embodiment of the present invention uses the above two chip units. The metal pads of the chip units are respectively arranged on both sides of the distributed feedback semiconductor laser chip, that is, as shown in FIG. 4 , the metal pads 11 of the first DFB semiconductor laser chip unit 10 are arranged on the leftmost The metal pads 21 of the DFB semiconductor laser chip unit 20 are arranged on the far right side of the chip, so that there is a certain distance between the two.

Using the above design, this embodiment also simulates the SMSR results of the above two active regions under different grating end phases. FIG. 7 is a schematic diagram showing the simulation result of the side mode suppression ratio of the DFB semiconductor laser chip in FIG. 4 under different grating end phases. The width Wa of the first active region is 1.2um, the width of the second active region Wb is 1.4um, and the difference between the output wavelengths of the two is 2um. It can be seen from FIG. 7 that the statistical yield of the single-mode curve corresponding to the second active region with the phase change (subject to greater than 35 dB) is very different from the curve law corresponding to the first active region. At any grating end phase, the SMSRs of the two chip units are always in a distribution of one high and one low, thus ensuring that the probability of selecting a laser with a high SMSR between the above two DFB semiconductor laser chip units is much greater than that of a single laser. The high SMSR yield of the first DFB semiconductor laser chip unit 10 or the second DFB semiconductor laser chip unit 20 .

The DFB semiconductor laser chips with different wavelengths provided by the examples of the present invention are not limited to designing two parallel chip units with different widths of active regions within one laser chip area. Multiple chip units such as three or four can also be designed in parallel. As the number of chip units in a laser chip increases, the size of the corresponding laser chip may also increase. Therefore, in practical applications, the design needs to be comprehensively considered according to the requirements of chip yield and output.

Further, when the DFB semiconductor laser chip is designed with three or more chip units, in order to save the chip area, the metal pads of the chip units can also be designed on the adjacent chip units, for example, the third The metal pads of one chip unit are arranged on the metal electrodes of the second chip unit. At the same time, in order to avoid the contact of the metal electrodes of the two chip units, passivation is also deposited on the surface of the metal electrodes of the second chip unit. membrane.

In addition, the above-mentioned DFB semiconductor laser chip with different wavelengths is not limited to the above-mentioned buried waveguide structure, and may also be a ridge waveguide structure.

It should be noted that, in the prior art, due to factors such as errors, the width of the first active region and the width of the second active region are not absolutely the same. Even if the same cleavage process is used, the resulting first The width of the source region and the width of the second active region cannot be absolutely the same, which is consistent with the solution of the embodiment of the present invention from the description, but the prior art does not care about this absolute difference, but is based on factors such as tolerance errors. , considered to be the same.

Although the absolute difference also has an effect on the wavelength, this effect is not sufficient for the purpose of the present invention. In the embodiment of the present invention, from the perspective of laser design, the width of the first active region and the width of the second active region are designed to be different, which is a deliberately pursued difference, and this difference is different from the prior art. , this difference can have a strong influence on the wavelength emitted by the laser, which is the purpose of the present invention.

Based on the above-mentioned structure of the DFB semiconductor laser chip with different wavelengths, this embodiment also provides a method for fabricating the DFB semiconductor laser chip with different wavelengths.

First, the preparation process of the DFB semiconductor laser chip with the buried waveguide structure is introduced. Specifically include the following steps:

Step S110: forming an active region on the substrate.

Step S120: preparing a grating on the active region.

Specifically, the method of direct electron beam exposure, holographic lithography, etc. can be used to make grating stripes on the stripe structure in the active area, and then wet etching or dry etching methods are used to prepare the upper waveguide in the active area. A uniform grating is engraved on the layer.

Then, a layer of p-type InP material is grown on the grating layer to protect the grating layer. Specifically, MOCVD (Metal-organic Chemical Vapor Deposition) is used to perform regrowth on the grating layer on the above-mentioned wafer on which the grating is formed.

Step S130 : preparing a periodically arranged active region strip structure on the active region formed with the grating, wherein each chip period includes a first active region and a second active region with different widths .

Specifically, a protective mask is first prepared on the wafer on which the quantum well active region is formed, and then, through the steps of photolithography, etching, etc., the above-mentioned mask is formed into a strip pattern that is periodically arranged on the wafer. , and at least two strip patterns with different widths are included in one chip cycle. Finally, using the above protective mask as a mask, the buried waveguide is prepared by wet etching or dry etching. Since the protective mask is used in one chip cycle It includes at least two strip-shaped structures with different widths, so corresponding to each chip period, at least two active area strip-shaped structures with different widths are included. 8 is a cross-sectional view of preparing active region mesas with different widths on a wafer having quantum well active regions formed according to an embodiment of the present invention. As shown in FIG. 8 , one chip cycle includes two chip units. Since the widths of the protective masks 151 and 251 of the two chip units are different, the widths of the corresponding two active regions Wa and Wb are also different. .

Step S140 : preparing a reverse PN junction, a P-type confinement layer, an ohmic contact layer and a metal electrode on the wafer on which the active region stripe structure and the grating are formed to obtain a wafer with a plurality of distributed feedback semiconductor laser chips .

Specifically, MOCVD (Metal-organic Chemical VaporDeposition) is used to sequentially perform regrowth on the grating layer, reverse PN junction regrowth, As well as the regrowth of the P-type confinement layer and the ohmic contact layer, as shown in FIG. 9 , it is a schematic cross-sectional structure diagram after growing the reverse PN junction, the P-type confinement layer and the ohmic contact layer on the wafer in FIG. 8 . Finally, P-side and N-side metal electrodes are prepared on the above-mentioned wafer through a die preparation process, so as to obtain a wafer with a plurality of distributed feedback semiconductor laser chips.

Step S150 : performing cavity end face coating and chip dissociation on the wafer having a plurality of distributed feedback semiconductor laser chips to obtain a plurality of independent distributed feedback semiconductor laser chips.

Specifically, according to the cavity length requirements of the DBF semiconductor laser chip, the above-mentioned wafer is dissociated into a plurality of bars and the front and rear exit surfaces are coated, and then the coated bars are dissociated according to the preset chip cycle. , and then multiple independent distributed feedback semiconductor laser chips are obtained. Since each chip cycle includes at least two strip-shaped structures of active regions with different widths, the laser chip obtained by dissociation also includes at least two distributed feedback semiconductor laser chips with different widths of active regions unit. Moreover, in a laser chip, the dissociation positions of each grating are formed when the bars are dissociated at the same time, so the phase of each grating segment of each grating in the chip is also the same.

Further, the implementation of the present invention also provides a method for preparing a DFB semiconductor laser chip with a ridge waveguide structure. Specifically include the following steps:

Step S210: Prepare a uniform grating on the P-waveguide layer in the wafer on which the quantum well active region is formed.

Specifically, the method of direct electron beam exposure, holographic lithography, etc. can be used to make grating stripes on the stripe structure in the active area, and then wet etching or dry etching methods are used to prepare the upper waveguide in the active area. A uniform grating is engraved on the layer.

Step S220 : growing a P-type confinement layer and an ohmic contact layer on the wafer on which the grating is formed.

Specifically, a P-type confinement layer and an ohmic contact layer are sequentially grown on the above-mentioned wafer on which the grating is formed by using MOCVD.

Step S230: Prepare periodically arranged ridge waveguides on the wafer on which the ohmic contact layer is formed, wherein each chip cycle includes at least two ridge waveguides with different widths.

Specifically, the above-mentioned mask can be formed with strip patterns periodically arranged on the wafer by means of photolithography, and at least two strip patterns with different widths are included in one chip cycle. A resist or other substance is used as a protective mask, and the ridge waveguide is prepared by wet etching or dry etching. Since each chip period includes at least two strip-shaped structures in the active region with different widths by photolithography, after the ridge waveguide is prepared, each chip period includes at least two ridge waveguides with different widths. Correspondingly, each One chip cycle also includes at least two active regions with different widths. It should be noted that, for a ridge waveguide type laser chip, the active region in the embodiment of the present invention refers to the active region corresponding to the ridge waveguide.

Step S240 : preparing metal electrodes on the wafer on which the ridge waveguide structure is formed to obtain a wafer having a plurality of distributed feedback semiconductor laser chips.

P-face and N-face metal electrodes are prepared on the above wafer through a die preparation process to obtain a wafer with a plurality of distributed feedback semiconductor laser chips.

Step S250 : performing cavity end face coating and chip dissociation on the wafer having a plurality of distributed feedback semiconductor laser chips to obtain a plurality of independent distributed feedback semiconductor laser chips.

Based on the above-mentioned multi-waveguide DFB semiconductor laser chips with different widths of active regions, an embodiment of the present invention further provides an optical module, the optical module includes components such as an optical transmitter, an optical receiver, and a microprocessor. The light transmitter is provided with the DFB semiconductor laser chip provided by the embodiment of the present invention.

Each embodiment in this specification is described in a progressive manner, and the same and similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments, and the relevant points. Please refer to the partial description of the method embodiment. Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. This application is intended to cover any variations, uses or adaptations of the invention which follow the general principles of the invention and which include common knowledge or conventional techniques in the art to which the invention is not invented . The specification and examples are to be regarded as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

It should be understood that the present invention is not limited to the precise structures described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims (10)

1. a distributed feedback semiconductor laser chip, is characterized in that, comprises: substrate; a first active region and a second active region disposed on the substrate, wherein the widths of the first active region and the second active region are different; and, a first grating disposed on the first active region, the light emitted by the first active region undergoes Bragg reflection at the first grating; a second grating disposed on the second active region, where the light emitted by the second active region undergoes Bragg reflection at the second grating; The end faces of the gratings formed by dissociation of the first grating and the second grating have the same phase; The chip unit corresponding to the first active area and the chip unit corresponding to the second active area have the same reflectivity of the front light exit cavity surface and the same reflectivity of the rear light exit cavity surface; The first grating and the second grating are of the same type, period, total grating length and their positions in the corresponding chip units. 2 . The distributed feedback semiconductor laser chip according to claim 1 , wherein the width difference between the first active region and the second active region is determined according to the first active region and the second active region. 3 . The wavelength difference emitted by the zone is greater than or equal to 1nm. 3 . The distributed feedback semiconductor laser chip according to claim 1 , wherein the distributed feedback semiconductor laser chip comprises a buried waveguide semiconductor laser chip, and the width difference between the first active region and the second active region is equal to 3 . 0.2 to 0.5 μm. 4 . The distributed feedback semiconductor laser chip according to claim 1 , wherein the upper limit of the width of the first active region and the width of the second active region is set according to the requirement that the chip operates in the fundamental transverse mode. 5 . and the lower limit of the width is set according to the slope efficiency of the chip meeting the preset efficiency value. 5. The distributed feedback semiconductor laser chip according to claim 1, wherein an isolation trench is further provided on the substrate, wherein: The isolation trench is located between the first active region and the second active region, and the isolation trench extends from the surface of the chip down into the substrate. 6. The distributed feedback semiconductor laser chip according to claim 1, wherein the chip further comprises: The first metal pad and the second metal pad are respectively arranged above the first grating and the second grating, wherein: The first metal pad and the second metal pad are respectively disposed on two sides of the chip. 7 . The distributed feedback semiconductor laser chip according to claim 1 , wherein the distributed feedback semiconductor laser chip comprises a buried waveguide semiconductor laser chip or a ridge waveguide semiconductor laser chip. 8 . 8. A method for preparing a distributed feedback semiconductor laser chip, wherein the method comprises: forming an active region on the substrate; preparing a grating on the active region; preparing a periodically arranged active area stripe structure on the active area formed with the grating, wherein each chip period includes a first active area and a second active area with different widths; preparing a reverse PN junction, a P-type confinement layer, an ohmic contact layer and a metal electrode on the wafer formed with the active region stripe structure and the grating to obtain a wafer with a plurality of distributed feedback semiconductor laser chips; Performing cavity end face coating and chip dissociation on the wafer with a plurality of distributed feedback semiconductor laser chips to obtain a plurality of independent distributed feedback semiconductor laser chips; Wherein, the chip unit corresponding to the first active area and the chip unit corresponding to the second active area have the same reflectivity of the front light exit cavity surface and the same reflectivity of the rear light exit cavity surface; The first grating corresponding to the first active region and the second grating corresponding to the second active region have the same phase of grating end faces formed by dissociation; The first grating and the second grating are of the same type, period, total grating length and their positions in the corresponding chip units. 9. A method for preparing a distributed feedback semiconductor laser chip, wherein the method comprises: fabricating a uniform grating on a P-waveguide layer in a wafer formed with quantum well active regions; growing a P-type confinement layer and an ohmic contact layer on the wafer formed with the grating; Periodically arranged ridge waveguides are prepared on the wafer on which the ohmic contact layer is formed, wherein each chip cycle includes at least two ridge waveguides with different widths, the ridge waveguides include a first ridge waveguide and a second ridge waveguide Two ridge waveguides, the first ridge waveguide corresponds to the first active region, and the second ridge waveguide corresponds to the second active region; preparing metal electrodes on the wafer formed with the ridge waveguide structure to obtain a wafer with a plurality of distributed feedback semiconductor laser chips; Performing cavity end face coating and chip dissociation on the wafer with a plurality of distributed feedback semiconductor laser chips to obtain a plurality of independent distributed feedback semiconductor laser chips; Wherein, the chip unit corresponding to the first active area and the chip unit corresponding to the second active area have the same reflectivity of the front light exit cavity surface and the same reflectivity of the rear light exit cavity surface; The first grating corresponding to the first active region and the second grating corresponding to the second active region have the same phase of grating end faces formed by dissociation; The first grating and the second grating are of the same type, period, total grating length and their positions in the corresponding chip units. 10. An optical module, characterized in that the optical module comprises an optical transmitter, and the optical transmitter is provided with the distributed feedback semiconductor laser chip according to any one of claims 1-7.

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