Compact power balance multi-wavelength laser device and manufacturing method thereof

Abstract

The invention discloses a compact power balance multi-wavelength laser device and a manufacturing method thereof. The device comprises a multi-channel DFB laser array, a plurality of second-level SOAs, a third-level Y combiner and a first-level SOA. A grating of the DFB laser array is a plurality of grating units which are periodically and gradually changed in a laser cavity; and equivalent pi phase shifts are introduced among the sections, so that accurate wavelength interval control and stable single-mode output are realized. The device is formed by stacking an n-type InP substrate, a buffer layer, an n-type InAlGaAs lower limiting layer, a multi-quantum well layer, a p-type InGaAsP upper limiting layer, a grating layer, a p-type InP cladding, a p-type InGaAsP transition layer and a p-type InGaAs contact layer. By adjusting the working current of the two-stage SOA and DFB laser devices, multi-wavelength laser light can be output at the same time under a compact structure, and the multi-wavelength laser device has the advantages of being uniform in wavelength interval, balanced in power and high in single-mode stability.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, and in particular relates to a compact power-balanced multi-wavelength laser device and a manufacturing method thereof. Background Art

[0002] With the rapid advancement of silicon photonics technology, optical I / O technology has been widely regarded as an important alternative to traditional electrical I / O technology. Due to the limitation of the number of package pins, traditional electrical I / O technology has gradually approached its performance limit and is unable to meet the stringent requirements of high-speed, high-density chip-to-chip interconnection. In contrast, optical I / O technology, with its significant advantages of high bandwidth, low latency, low power consumption and high capacity, provides a more ideal solution for next-generation communication and computing applications, especially in the pursuit of high-speed data transmission and high-density interconnection scenarios, showing great application potential.

[0003] Among the core components of optical I / O technology, multi-wavelength lasers (MWLs) play a vital role. MWLs can provide multiple light sources with different wavelengths at the same time and support parallel data transmission. Their performance is directly related to the key performance indicators of the entire system, such as communication rate, capacity, delay, and bit error rate. With the continuous increase in demand for optical communications, the development of high-performance multi-wavelength laser sources has become the key to improving the overall performance of optical I / O technology.

[0004] In many MWL studies, DFB laser arrays have become a more ideal choice due to their stable mode, simple operation mechanism, and uniform wavelength spacing. However, when multiple DFB lasers work in parallel, thermal crosstalk is difficult to avoid, which will lead to an increase in the error of wavelength spacing. In order to achieve stable and uniform wavelength spacing, it is usually necessary to fine-tune the operating current of each laser, but this operation often causes problems such as uneven output power, which in turn has an adverse effect on the performance of the overall system. Although technologies such as flip-chip welding, nonlinear polarization rotation effects, and optical attenuator arrays have been proposed to solve these problems, they either increase the complexity of the process or are difficult to achieve monolithic integration.

[0005] Therefore, how to design an efficient multi-wavelength laser array that can accurately control the wavelength spacing and achieve power balance is still a technical problem that needs to be solved in this field. In view of this situation, the present invention proposes a compact power-balanced multi-wavelength laser device and a manufacturing method thereof, in order to provide a new idea for solving this problem. Summary of the invention

[0006] In view of the problems raised by the background technology, the present invention provides a compact power-balanced multi-wavelength laser device and a manufacturing method thereof, introduces a two-stage semiconductor optical amplifier (SOA) which has little effect on the accuracy of the output wavelength of the DFB laser to adjust the output multi-wavelength power, and makes the wavelength interval uniform by fine-tuning the working current of the multi-channel DFB laser to ensure balanced output power, with simple structure, low power consumption and high integration.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution: a compact power balanced multi-wavelength laser device, including: a multi-channel DFB laser array, a two-stage SOA, a three-stage Y combiner, and a one-stage SOA.

[0008] Wherein, the multi-channel DFB laser array includes a plurality of single DFB lasers arranged on a plurality of different waveguides; There are multiple second-level SOAs, which correspond one-to-one to the multi-channel DFB laser arrays, and are respectively arranged at the front end of a single DFB laser. The corresponding DFB lasers are in the same waveguide, and the multiple waveguides are combined into a single waveguide through a three-level Y combiner. The primary SOA is arranged at the front end of the laser device for amplifying the output optical signal; the laser device achieves output with uniform wavelength interval and balanced power by adjusting the working current of the secondary SOA and the multi-channel DFB laser.

[0009] Preferably, the grating of the multi-channel DFB laser array is divided into multiple grating units, and an equivalent π phase shift (π-EPS) is introduced between each grating unit segment to achieve precise wavelength interval control and stable single-mode output.

[0010] Preferably, the grating layer of the multi-channel DFB laser array adopts a reconstruction equivalent chirp method to form a linear gradient of the grating period through holographic exposure and micron-level photolithography.

[0011] Preferably, the output wavelengths of the multiple DFB lasers vary at equal intervals and can be adjusted according to demand, and are controlled by an internal multi-segment periodic linear gradient grating unit.

[0012] Preferably, the laser device is composed of, from bottom to top, an n-type InP substrate, an n-type InP buffer layer, an n-type InAlGaAs lower confinement layer, an InAlGaAs multiple quantum well layer, a p-type InGaAsP upper confinement layer, a p-type InGaAsP grating layer, a p-type InP cladding layer, a p-type InGaAsP transition layer and a p-type InGaAs contact layer.

[0013] Preferably, the p-type InGaAsP grating layer is composed of a laser grating.

[0014] Preferably, in the InAlGaAs multiple quantum well layer, the InGaAlAs multiple quantum well serves as a gain medium, covering the wavelength output range of the laser device.

[0015] Preferably, the multi-channel DFB laser array is an 8-channel DFB laser array, which is formed by 8 DFB lasers connected in parallel, each DFB laser is arranged in a waveguide, and the 8 waveguides are placed side by side in space; there are 8 secondary SOAs, each secondary SOA only acts on the DFB laser in the same waveguide, and has little effect on the output wavelength accuracy of the DFB laser it acts on.

[0016] Preferably, by adjusting the current of 8 secondary SOAs, the power of each channel of the 8-channel DFB laser is adjusted without increasing the wavelength spacing error; the wavelength spacing is made uniform by fine-tuning the working current of the 8-channel DFB laser, and the output power is balanced by adjusting the working current of the 8 secondary SOAs.

[0017] The technical solution adopted by the present invention also includes: a method for manufacturing a compact power-balanced multi-wavelength laser, using the above-mentioned compact power-balanced multi-wavelength laser device, the manufacturing method includes the following steps: Step 1: growing an n-type InP buffer layer, an n-type InAlGaAs lower confinement layer, an InAlGaAs multi-quantum well layer, a p-type InGaAsP upper confinement layer, and a p-type InGaAsP grating layer on an n-type InP substrate in sequence by a metal organic compound vapor deposition method; Step 2: The grating layer is designed to form a linear gradient of the grating period by using a reconstruction equivalent chirp method, and is prepared by holographic exposure and micron-level photolithography; Step 3: grow a p-type InP cladding layer, a p-type InGaAsP transition layer and a p-type InGaAs contact layer in sequence above the grating layer to form a ridge waveguide structure, and coat anti-reflection films at both ends to complete the preparation of the laser.

[0018] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects: 1. The laser of the present invention uses a linear gradient grating structure with a gradually changing grating period to enhance grating feedback, so that the laser bandgap width is increased, thereby covering the laser lasing wavelength range. By introducing a phase shift between each segment of the grating structure without affecting the gradient of each segment of the grating structure, the laser resonant cavity can meet the phase matching condition at the phase shift to output a single-mode laser. Using a multi-electrode one-to-one power-on method, each phase shift shares a laser resonant cavity, realizing flattened output of each wavelength.

[0019] 2. The present invention adjusts the output multi-wavelength power by introducing a secondary SOA. Since the current adjustment of the secondary SOA has little effect on the wavelength of the tandem laser, the wavelength interval is uniform by fine-tuning the working current of multiple DFB lasers, and then the working current of multiple secondary SOAs is adjusted to balance the output power without affecting the wavelength accuracy. The present invention realizes multi-wavelength coherent flattening output through a single laser, providing a design of a power-balanced multi-wavelength source with a simple structure, low power consumption, and high integration for the next generation of communication and computing applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of a compact power-balanced multi-wavelength laser device of the present invention; Figure 2 It is a schematic diagram of the compact power-balanced multi-wavelength laser grating structure of the present invention; Figure 3 This is a SEM image of the waveguide cross section of the compact power-balanced multi-wavelength laser device of the present invention; Figure 4 This is a physical picture of a compact power-balanced multi-wavelength laser device in an embodiment of the present invention; Figure 5 It is the 8-channel laser test spectrum and wavelength linear fitting diagram in the embodiment of the present invention; Figure 6 It is a statistical diagram of the output power and wavelength shift of each channel when the injection current of the second-stage SOA of the 8-channel laser in the embodiment of the present invention changes from 0 to 30mA; Figure 7 The figure is a graph showing the single-mode characteristics and output power characteristics of the laser and the output power variation when the primary SOA current of the 8-channel laser in the embodiment of the present invention changes. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the application is further elaborated in detail below in conjunction with the accompanying drawings. The described embodiments are only a part of the embodiments involved in the present invention. All non-innovative embodiments of other researchers in the field on this embodiment belong to the protection scope of the present invention. At the same time, for the step numbering in the embodiment of the present invention, it is only set for the convenience of explanation, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0022] In one embodiment of the present invention, a compact power-balanced multi-wavelength laser device is structured as follows: Figure 1 As shown, it includes: an 8-channel DFB laser array, 8 second-level SOAs, a three-level Y combiner, and 1 first-level SOA.

[0023] The 8-channel DFB laser array is formed by 8 single DFB lasers arranged in parallel on different waveguides. Each laser is arranged on a waveguide, and the 8 waveguides are placed side by side in space. The output wavelength of a single DFB laser can be freely designed according to the actual application requirements.

[0024] Furthermore, the grating of the 8-channel DFB laser array is divided into multiple grating units, such as Figure 2 As shown, the grating period of the grating unit segment gradually changes to achieve wavelength interval control, and an equivalent π phase shift is introduced between each segment of the grating unit to achieve phase matching between adjacent grating units. The existing multi-phase shift structure thus realizes multi-wavelength lasing output.

[0025] In this embodiment, Figure 3 As shown, the compact power-balanced multi-wavelength laser device is composed of an n-type InP substrate, an n-type InP buffer layer, an n-type InAlGaAs lower confinement layer, an InAlGaAs multiple quantum well layer, a p-type InGaAsP upper confinement layer, a p-type InGaAsP grating layer, a p-type InP cladding layer, a p-type InGaAsP transition layer and a p-type InGaAs contact layer stacked from bottom to top, wherein the grating layer is composed of a laser grating.

[0026] In this embodiment, the linear gradient grating structure and the phase shift structure between each grating segment are realized by using the reconstruction equivalent chirp technology, and the equivalent linear gradient is realized by using the equivalent grating structure.

[0027] It is particularly important to note that the laser device of this embodiment introduces a two-stage SOA that has less impact on the wavelength deviation of the series laser, adjusts the output multi-wavelength power, and makes the wavelength interval uniform by fine-tuning the working current of the 8 DFB lasers, and then adjusts the working current of the 8 two-stage SOAs to balance the output power without affecting the wavelength accuracy.

[0028] Furthermore, in this embodiment, the manufacturing method of the compact power-balanced multi-wavelength laser device is as follows: An n-type doped substrate is used, and an n-type doped InP buffer layer, an n-type doped confinement layer and an undoped confinement layer are sequentially grown on the substrate by vapor deposition of metal organic compounds; wherein the relevant confinement layer is used for light field confinement and carrier confinement.

[0029] Afterwards, an InGaAlAs multiple quantum well structure is grown, and then a confinement layer is designed above the quantum well, and an InGaAsP grating layer is grown above the confinement layer. Its structure is the linear gradient grating period involved, and its equivalent linear gradient grating can be designed by reconstructing the equivalent chirp technology, and its equivalent grating period is linearly gradient.

[0030] A p-type InP is grown on the grating layer for burying, a waveguide layer related corrosion barrier layer is grown on the contact layer, and then the waveguide layer is grown.

[0031] In particular, this embodiment introduces multiple phase shifts at equal intervals in the linear gradient grating period, the Bragg grating wavelength change of the overall laser is set to 6.4 nm, and the wavelength spacing between adjacent phase shifts is 0.8 nm, so that the first grating and the second grating share one phase shift, similar to the above-mentioned single phase shift structure. By setting this phase shift structure, it is achieved that two gratings share one phase shift.

[0032] Furthermore, the compact power balanced multi-wavelength laser device of this embodiment is shown in Figure 4 As shown, the relevant test results of this embodiment are as follows Figures 5 to 7 shown.

[0033] Figure 5 (a) is the spectrum diagram of 8-channel laser test. Figure 5 (b) is the linear fitting diagram of the test wavelength. It can be seen that at the operating temperature of 25°C, when the injection currents of the DFB laser array are 60.5, 54.1, 52.5, 50.2, 49.8, 51.4, 55.7, and 62.3 mA, and the injection currents of the secondary SOA are 17.5, 18.2, 20.6, 23.2, 25.8, 22.9, 20.3, and 17.3 mA, respectively, the output wavelengths of the DFB laser array are They are 1544.47, 1545.32, 1546.11, 1546.87, 1547.64, 1548.41, 1549.20 and 1550.02nm respectively. It can also be concluded from the spectrum test that 8 wavelengths can be lased during actual use, the channel spacing is uniform, the maximum wavelength deviation is only 0.03nm, the side mode suppression ratio (SMSR) is high, the output optical power is relatively flat, and the maximum output power deviation is only 1.01dB.

[0034] Figure 6 (a) shows the relationship between the output power of the laser and the injection current of the secondary SOA during single-channel lasing. The results show that by applying different currents to the secondary SOAs of different channels, the output powers of multiple channels can be made consistent. Figure 6 It can be seen from (b) that when the secondary SOA current changes within 30mA, the maximum output wavelength shift of the 8 channels is only 0.08nm, which further shows that the secondary SOA has little effect on the wavelength shift of the laser.

[0035] Figure 7 (a) shows the output power amplification capability of the first-stage SOA for multi-channel lasers. When the injection current of the first-stage SOA is 150mA, the output power can reach 20mW. Figure 7 (b) shows the result that when the primary SOA current changes from 50 to 150mA, the laser can still maintain good single-mode characteristics, the side mode suppression ratio is above 42dB, and the intensity standard deviation (SDOI) of the eight-channel output power is less than 0.6dB, which further shows that the laser device of the present invention can maintain the consistency of output power while having high power output. It can be judged that the designed 8-channel multi-wavelength laser can be applied to the above-mentioned related application fields.

[0036] In summary, the present invention provides a multi-wavelength source design scheme, which adopts a linear gradient grating structure to increase the bandgap width and provide feedback of multiple wavelengths. Phase shift is introduced at the equal divisions of the overall grating to achieve multiple Bragg wavelength lasing at the phase shift position. The wavelength interval is made uniform by fine-tuning the working current of the multi-channel DFB laser, and the output power is balanced by adjusting the working current of multiple secondary SOAs; the threshold gain of each wave is low, the overall laser threshold current is reduced, and the photoelectric conversion efficiency is increased. At the same time, due to sharing the same resonant cavity, a flattened coherent wavelength can be output. The present invention can ultimately achieve multi-wavelength output of a single laser, balanced output power, simple structure, low power consumption, and high integration.

[0037] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A compact power-balanced multi-wavelength laser device, characterized in that: include: Multi-channel DFB laser array, two-stage SOA, three-stage Y combiner, and one-stage SOA; The multi-channel DFB laser array includes a plurality of single DFB lasers arranged on a plurality of different waveguides; There are multiple secondary SOAs, which correspond one to one with the multi-channel DFB laser arrays, and are respectively arranged at the front end of a single DFB laser, and are in the same waveguide with the corresponding DFB laser. The multiple waveguides are combined into a single waveguide through a three-stage Y combiner; The primary SOA is arranged at the front end of the laser device and is used to amplify the output optical signal; the laser device achieves output with uniform wavelength interval and balanced power by adjusting the working current of the secondary SOA and the multi-channel DFB laser.

2. The compact power-balanced multi-wavelength laser device according to claim 1, characterized in that: The grating of the multi-channel DFB laser array is divided into multiple grating units, adopts a linear gradient grating structure, and introduces an equivalent π phase shift between each grating unit segment for wavelength interval control and stable single-mode output.

3. The compact power-balanced multi-wavelength laser device according to claim 2, characterized in that: The grating layer of the multi-channel DFB laser array adopts the reconstruction equivalent chirp technology, and forms a linear gradient of the grating period through holographic exposure and micron-level photolithography methods.

4. The compact power-balanced multi-wavelength laser device according to claim 3, characterized in that: The output wavelengths of multiple DFB lasers vary at equal intervals and are controlled according to demand through an internal multi-segment periodic linear gradient grating unit.

5. The compact power-balanced multi-wavelength laser device according to claim 1, characterized in that: The laser device is composed of an n-type InP substrate, an n-type InP buffer layer, an n-type InAlGaAs lower confinement layer, an InAlGaAs multi-quantum well layer, a p-type InGaAsP upper confinement layer, a p-type InGaAsP grating layer, a p-type InP cladding layer, a p-type InGaAsP transition layer and a p-type InGaAs contact layer stacked in sequence from bottom to top.

6. The compact power-balanced multi-wavelength laser device according to claim 5, characterized in that: The p-type InGaAsP grating layer is composed of a laser grating.

7. The compact power-balanced multi-wavelength laser device according to claim 5, characterized in that: In the InAlGaAs multi-quantum well layer, the multi-quantum well is an InGaAlAs multi-quantum well, which serves as a gain medium to cover the wavelength output range of the laser device.

8. The compact power-balanced multi-wavelength laser device according to claim 1, characterized in that: The multi-channel DFB laser array is an 8-channel DFB laser array, which is formed by 8 DFB lasers connected in parallel, each DFB laser is arranged on a waveguide, and the 8 waveguides are placed side by side in space; there are 8 secondary SOAs, and each secondary SOA only acts on the DFB laser on the same waveguide.

9. The compact power-balanced multi-wavelength laser device according to claim 8, characterized in that: By adjusting the current of 8 secondary SOAs, the power of each channel of the 8-channel DFB laser is adjusted while controlling the wavelength spacing error; the wavelength spacing is made uniform by fine-tuning the working current of the 8-channel DFB laser, and the output power is balanced by adjusting the working current of the 8 secondary SOAs.

10. A method for manufacturing a compact power-balanced multi-wavelength laser, applied to the compact power-balanced multi-wavelength laser device according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: Step 1: growing an n-type InP buffer layer, an n-type InAlGaAs lower confinement layer, an InAlGaAs multi-quantum well layer, a p-type InGaAsP upper confinement layer, and a p-type InGaAsP grating layer on an n-type InP substrate in sequence by a metal organic compound vapor deposition method; Step 2: The grating layer is designed to form a linear gradient of the grating period by using a reconstruction equivalent chirp method, and is prepared by holographic exposure and micron-level photolithography; Step 3: grow a p-type InP cladding layer, a p-type InGaAsP transition layer and a p-type InGaAs contact layer in sequence above the grating layer to form a ridge waveguide structure, and coat anti-reflection films at both ends to complete the preparation of the laser.

Images