A multi-wavelength semiconductor laser based on dual-channel multiplexed output

Abstract

The present invention discloses a multi-wavelength semiconductor laser based on dual-channel multiplexed output. It mainly consists of N + 1 input semiconductor optical amplifiers, a wavelength division multiplexer, two output semiconductor optical amplifiers, and an optical combiner. Among them, the input semiconductor optical amplifiers, the wavelength division multiplexer, and the output semiconductor optical amplifiers jointly form an optical resonator to excite lasers of corresponding wavelengths, and the light emitted by the two output semiconductor optical amplifiers is jointly output after passing through the optical combiner; by designing the working wavelength interval of the input and output ports of the wavelength division multiplexer, the simultaneous output of 2N continuous wavelengths is realized. Compared with the existing semiconductor multi-wavelength semiconductor lasers, the present invention has a more compact design method and realizes the output of more channels of wavelengths with fewer semiconductor optical amplifiers.

Description

Technical Field

[0001] The present invention relates to a multi-wavelength semiconductor laser, and more particularly to a multi-wavelength semiconductor laser based on dual-channel multiplexed output. Background Art

[0002] A multi-wavelength semiconductor laser is a laser that can simultaneously output laser signals of multiple wavelengths and has wide applications in the fields of optical communication, optical sensing, optical computing, etc. In a wavelength division multiplexing passive optical network (WDM-PON), a multi-wavelength semiconductor laser is often used as the central node light source. By uploading and downloading lights of different wavelengths at each node and reusing each wavelength, the demand for lasers at each node is reduced, effectively reducing the cost of the system. Multi-wavelength semiconductor lasers are also commonly used in optical sensing. By jointly detecting multiple wavelengths, the sensing range and accuracy can be improved. In the field of optical computing, using a multi-wavelength semiconductor laser as the light source, computing data can be independently processed at each wavelength, giving full play to the parallel computing ability of the optical platform. For multi-wavelength semiconductor lasers, the current main research directions are to reduce the manufacturing cost of the lasers, increase the number of output wavelengths, and improve the quality of the output laser.

[0003] Traditional multi-wavelength semiconductor lasers are based on fiber lasers. Using the nonlinear effect of the fiber, a single-wavelength laser can be expanded into multi-wavelength output. Currently, such lasers can already achieve the output of more than a hundred wavelengths of light. However, fiber lasers are large in size, high in cost, and have poor wavelength uniformity. Another implementation method is a semiconductor laser array. An array is composed of multiple single-wavelength lasers, and the finally output light is combined into one beam after passing through an optical fiber combiner. The multi-wavelength semiconductor laser thus formed has a compact structure, its output performance is the same as that of a single-wavelength laser, and the lights of each wavelength can be independently controlled, with higher flexibility. However, since its output is combined by multiple lasers, an N×1 optical fiber combiner is required for an N-channel multi-wavelength semiconductor laser, which increases the complexity and cost of the system.

[0004] Based on the intracavity mode selection principle, a multi-wavelength semiconductor laser can also be constructed. An array of semiconductor optical amplifiers and a wavelength division multiplexer are integrated together. A resonant cavity is formed between the wavelength division multiplexer and different semiconductor optical amplifiers, and its lasing wavelength corresponds to the wavelength with the minimum loss of the wavelength division multiplexer. In this way, multiple semiconductor optical amplifiers work simultaneously, and multiple wavelengths can be output simultaneously. Such a laser also has the advantages of small size and low cost of semiconductor lasers, and all wavelengths are output from one port, without the need to use an optical fiber combiner. However, for such multi-wavelength semiconductor lasers, as the number of wavelengths increases, more semiconductor optical amplifiers need to be used, and the size of the integrated wavelength division multiplexer also increases accordingly, and its output performance will deteriorate, which limits the further increase in the number of wavelengths of such multi-wavelength semiconductor lasers. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a semiconductor multi-wavelength semiconductor laser, which can achieve laser output of more wavelengths with fewer semiconductor optical amplifiers.

[0006] By designing the wavelength interval of the input and output ports of the wavelength division multiplexer, the present invention can achieve simultaneous output of 2N continuous wavelengths, with a smaller and more compact structure size and stronger functions.

[0007] The technical solution adopted by the present invention is as follows:

[0008] It mainly consists of an input semiconductor optical amplifier array, a wavelength division multiplexer, an output semiconductor optical amplifier array, two partial reflectors and a photo-coupler. The input semiconductor optical amplifier array is connected to the input port of the wavelength division multiplexer, one end of the output semiconductor optical amplifier array is connected to the output port of the wavelength division multiplexer, and the other end is connected to the photo-coupler through a partial reflector.

[0009] The input semiconductor optical amplifier array, the wavelength division multiplexer and the output semiconductor optical amplifier array form the laser light source part. Optical signals of multiple wavelengths are simultaneously output from the input semiconductor optical amplifier array to the wavelength division multiplexer for wavelength division multiplexing and combining, and are divided into two optical signals with multiple wavelengths and different wavelength sequences. The two optical signals are respectively input into two ports of the output semiconductor optical amplifier array with two paths. After being optically amplified by the output semiconductor optical amplifier array, the two output ends of the output semiconductor optical amplifier array respectively emit. Two optical signals with multiple wavelengths and different wavelength sequences are emitted from the two output ends of the output semiconductor optical amplifier array as the output light of the laser light source part. The two optical signals are respectively input into two partial reflectors and then input into the photo-coupler together for combining and output;

[0010] Both the input semiconductor optical amplifier array and the output semiconductor optical amplifier array are constructed based on the multi-channel semiconductor optical amplifier array structure.

[0011] Among them, the input semiconductor optical amplifier array and the output semiconductor optical amplifier array provide optical gain, the wavelength multiplexer selects the output wavelength, and the photo-coupler realizes simultaneous output of multiple wavelengths.

[0012] The wavelength division multiplexer has N + 1 input ports, and the N + 1 input ports are respectively connected to the N + 1 output ports of the input semiconductor optical amplifier array. The wavelength division multiplexer has 2 output ports, and the 2 output ports are respectively connected to the 2 output ports of the output semiconductor optical amplifier array. For the wavelength division multiplexer, lights of different wavelengths have different transmission losses when transmitted from one input port to one output port. The light of one wavelength has the minimum transmission loss, corresponding to the working wavelength between the input and output ports.

[0013] An optical signal sequence composed of N + 1 optical signals with working wavelengths spaced 2Δλ apart. The N + 1 optical signals of the optical signal sequence are respectively output from the input semiconductor optical amplifier array, pass through the N + 1 input ports of the wavelength division multiplexer, and then are input into the same output port of the wavelength division multiplexer. The optical signal sequences received by the two output ports of the wavelength division multiplexer differ by working wavelengths spaced 3Δλ apart. That is, the working wavelengths of the optical signal sequence output from one output port are λ 1 , λ 2 , …, λ N+1 . Among them, the adjacent working wavelengths are spaced 2Δλ apart. Then the working wavelengths of the optical signal sequence output from one output port are λ 1 + 3Δλ, λ 2 + 3Δλ, …, λ N+1 .

[0014] For the same output port of the wavelength division multiplexer, the N + 1 input ports correspond to N + 1 working wavelengths. In the wavelength sequence composed of the N + 1 working wavelengths, the adjacent two working wavelengths have equal intervals, and the interval is 2Δλ. Δλ represents the wavelength difference between adjacent wavelengths of the multi-wavelength output of the laser.

[0015] For the same input port of the wavelength division multiplexer, the 2 output ports correspond to 2 working wavelengths.

[0016] There are a total of 2N + 2 working wavelengths corresponding between the input and output ports of the wavelength division multiplexer. Among them, 2N wavelengths have the same wavelength interval Δλ and can be used as the output of the laser.

[0017] The input semiconductor optical amplifier array outputs two optical signals with a wavelength interval of 2Δλ at each output port and inputs them into one input port of the wavelength division multiplexer. The wavelengths of the two optical signals output from each output port of the input semiconductor optical amplifier array are all different.

[0018] After wavelength division multiplexing processing, the wavelength division multiplexer outputs two optical signal sequences at each output port. After being amplified by the output semiconductor optical amplifier, they enter their respective corresponding partial reflectors. Each optical signal sequence contains optical signals with N + 1 different operating wavelengths with a wavelength interval of 2Δλ. The wavelengths of all the optical signals in the two optical signal sequences output by the wavelength division multiplexer are different. The optical combiner combines the two optical signal sequences transmitted from the two partial reflectors into an optical signal sequence composed of 2N + 2 optical signals with different operating wavelengths, among which there is an equal interval of Δλ between 2N operating wavelengths. The other two operating wavelengths are respectively the minimum and maximum values among all the operating wavelengths, and they differ from the second smallest and second largest values among all the operating wavelengths by 2Δλ respectively.

[0019] Each partial reflector outputs the same optical signal sequence as that transmitted by the wavelength division multiplexer to the optical combiner. The optical combiner combines the two optical signal sequences transmitted from the two partial reflectors into an optical signal sequence composed of 2N + 2 optical signals with a wavelength interval of Δλ.

[0020] The input semiconductor optical amplifier array has N + 1 semiconductor optical amplifiers, which are connected to the input ports of the wavelength division multiplexer. The output semiconductor optical amplifier array has 2 semiconductor optical amplifiers, which are connected to the output ports of the wavelength division multiplexer. The wavelength division multiplexer has N + 1 input ports and 2 output ports.

[0021] The input semiconductor optical amplifier array, the wavelength division multiplexer, and the output semiconductor optical amplifier array together form 2N + 2 optical resonators. By applying current to the semiconductor optical amplifiers in the input semiconductor optical amplifier array and the output semiconductor optical amplifier array to provide optical gain, a total of 2N + 2 wavelengths of laser are excited. The output wavelengths correspond to the operating wavelengths between the input - output ports of the wavelength division multiplexer, and the wavelength interval between 2N wavelengths is Δλ.

[0022] One semiconductor optical amplifier in the input semiconductor optical amplifier array and one semiconductor optical amplifier in the output semiconductor optical amplifier array together with the wavelength division multiplexer form an optical resonator. For this optical resonator, the optical signals of each wavelength have different transmission losses, and the operating wavelength between this input - output channel of the wavelength division multiplexer has the minimum loss. When current is applied to the input semiconductor optical amplifier, the optical signal of this wavelength has the lowest threshold current in the resonator, and the laser signal corresponding to this wavelength can be excited in this resonator.

[0023] By designing the working wavelength intervals corresponding between different input and output ports of the wavelength division multiplexer, among the finally output 2N + 2 wavelengths, 2N wavelengths can have the same wavelength interval Δλ. The specific design method is that the working wavelength interval of the corresponding channels between the input ports of the wavelength division multiplexer is 2Δλ, and the working wavelength interval of the corresponding channels between the output ports of the wavelength division multiplexer is 3Δλ.

[0024] The wavelength division multiplexer is an etched diffraction grating or an arrayed waveguide grating.

[0025] The output semiconductor optical amplifier array is connected to the optical combiner through a partial reflector. The partial reflector reflects a part of the optical signals incident from the semiconductor optical amplifiers of the output semiconductor optical amplifier array to achieve laser resonance, and the other part of the optical signals is transmitted and transmitted to the combiner to achieve laser output.

[0026] Both the input semiconductor optical amplifier array and the output semiconductor optical amplifier array are multi-channel semiconductor optical amplifier arrays.

[0027] In the present invention, the input semiconductor optical amplifier array and the output semiconductor optical amplifier array must adopt the multi-channel semiconductor optical amplifier array made of group III-V semiconductor materials provided by the present invention, and cannot be composed of a conventional semiconductor optical amplifier arranged in an array. The situation is that the input semiconductor optical amplifier array and the output semiconductor optical amplifier array are respectively connected to the input and output ports of the wavelength division multiplexer. Adopting the multi-channel semiconductor optical amplifier array designed by the present invention can greatly reduce the spacing between semiconductor lasers, minimize the sizes of all parts, improve the overall integration, and the reduction of the sizes of all parts reduces the overall loss of the system and increases the output power of the laser.

[0028] Each semiconductor optical amplifier has a ridge waveguide structure, which can effectively limit the input current, improve the electro-optical conversion efficiency, and reduce the crosstalk between different semiconductor optical amplifiers. Each semiconductor optical amplifier is completed by one-time fabrication. The fabrication process is simple and the performance is the same, and a uniform multi-wavelength output effect can be achieved.

[0029] The multi-channel semiconductor optical amplifier array is made of group III-V semiconductor materials. Other devices such as one wavelength division multiplexer, two partial reflectors, and one optical combiner use passive materials such as silicon and silicon nitride. Such materials are used to achieve low-loss transmission of light.

[0030] The multi-channel semiconductor optical amplifier array is mainly fabricated in the following manner:

[0031] First, fabricate a wafer structure mainly composed of a substrate, a lower cladding layer, an active layer, and an upper cladding layer from bottom to top in sequence. The refractive index of the active layer material is higher than that of the upper and lower cladding layer materials.

[0032] Then, transfer the design pattern to the surface of the upper cladding layer through photolithography, and use wet etching or dry etching to remove the upper cladding layer, so that the upper cladding layer forms a ridge waveguide. Multiple ridge waveguides are directly fabricated according to the design pattern, and then the lower cladding layer and the active layer between adjacent ridge waveguides are over-etched to form deep etching grooves. Thus, each ridge waveguide of the upper cladding layer serves as a semiconductor optical amplifier, and deep etching grooves are provided between adjacent semiconductor optical amplifiers to separate them.

[0033] Next, deposit a silicon oxide insulating layer on the upper cladding layer and the exposed active layer, then open a window on the silicon oxide insulating layer and fabricate a P-type electrode connected to the upper cladding layer. Finally, after thinning and polishing the back of the substrate, fabricate an N-type electrode connected to the substrate.

[0034] Apply voltage / current to the P-type electrode and N-type electrode of each semiconductor optical amplifier to convert photons in the active layer and achieve optical gain.

[0035] Each semiconductor optical amplifier has the same waveguide length and is fabricated in an arrayed manner with the same spacing. An independent P-type electrode is fabricated on each semiconductor optical amplifier, and all semiconductor optical amplifiers use a common N-type electrode. Apply current independently to each semiconductor optical amplifier, thereby providing optical gain and switching action to the optical signal passing through the semiconductor optical amplifier.

[0036] When the current applied to the semiconductor optical amplifier is greater than the threshold current, the optical gain provided by the semiconductor optical amplifier in each optical resonator is greater than the loss in the optical resonator, and laser oscillation output is achieved in the optical resonator and finally output from the semiconductor optical amplifier of the output semiconductor optical amplifier array.

[0037] When the current applied to the semiconductor optical amplifier is less than or equal to the threshold current, the optical gain provided by the semiconductor optical amplifier in each optical resonator is less than the loss in the optical resonator, and the input optical signal is absorbed in the optical resonator without outputting an optical signal.

[0038] The lower cladding layer and the upper cladding layer adopt binary compound materials, where the upper cladding layer material is P-type doped and the lower cladding layer material is N-type doped. The active layer adopts a multi-quantum well material composed of a quaternary compound material.

[0039] In the multi-wavelength semiconductor laser of the present invention, each semiconductor optical amplifier is made of an active material that provides optical gain and light amplification functions, and parts such as a wavelength division multiplexer, two partial reflectors, and a light combining beam splitter are made of passive materials with relatively low optical losses. Each part can be integrated on the same chip through monolithic integration technology or hybrid integration technology to minimize the size.

[0040] In the monolithic integration technology, each part of the device is fabricated on the same III-V semiconductor material. The active layer of the semiconductor optical amplifier part is a quantum well material. After processes such as quantum well intermixing, butt joint regrowth, and biased quantum wells for the materials of other parts, the energy band of the quantum well changes, the absorption of light at the working wavelength decreases, and it is transformed into a passive material.

[0041] In the hybrid integration technology, the semiconductor optical amplifier part is fabricated on the III-V semiconductor material, and other parts are fabricated on silicon-based materials such as silicon-on-insulator (SOI) and silicon nitride. Such materials can achieve low-loss transmission of light. The two materials are integrated into the same chip by means of end-face coupling or vertical coupling, achieving high integration.

[0042] In the first embodiment, each part in the semiconductor multi-wavelength semiconductor laser is integrated on the same chip. The partial reflector is realized on the chip through a deep etching groove, and the beam combiner can be realized on the chip by means of a Y-branch beam combiner, a multimode interference coupler, etc. The input semiconductor optical amplifier array and the output semiconductor optical amplifier array are fabricated on the active material that can provide optical gain, and the wavelength division multiplexer, the partial reflector, and the light combining beam splitter are fabricated on the passive material with relatively low optical losses. The active material and the passive material can be integrated on the same substrate through monolithic integration or heterogeneous integration.

[0043] In the second embodiment, the input semiconductor optical amplifier array, the wavelength division multiplexer, the output semiconductor optical amplifier array, and the partial reflector are integrated on the same chip through monolithic integration or heterogeneous integration, and the partial reflector is realized through an etched end face or a cleaved end face. The beam combiner is a fiber beam combiner, and beam combining output is realized after being coupled with the partial reflector through a coupling lens.

[0044] The input semiconductor optical amplifier array, the wavelength division multiplexer, the output semiconductor optical amplifier array, the partial reflector, and the light combining beam splitter are integrated on the same chip through monolithic integration or hybrid integration.

[0045] The multi-channel semiconductor optical amplifier array is made of group III-V semiconductor materials and is used to convert electrons into photons to provide optical gain, switching, and active laser functions. Other devices such as a wavelength division multiplexer, two partial reflectors, and a fiber optic combiner outside the multi-channel semiconductor optical amplifier array use passive materials such as silicon and silicon nitride. Such materials are used to achieve low-loss transmission of light. The two materials are integrated on the same chip by end-face coupling or vertical coupling, so that the multi-wavelength optical emission-router of the present invention is realized through a hybrid integration technology.

[0046] The fiber optic combiner is used as the fiber optic combiner. A coupling lens is arranged at the output end of the fiber optic combiner and is coupled with the chip through the coupling lens to realize the combined output of the laser.

[0047] The innovation of the present invention lies in the combined output of multi-wavelength optical signals output from two output channels of the same wavelength division multiplexer through the dual-channel multiplexing output method. In this way, when realizing the output of the same number of wavelengths, the present invention requires fewer semiconductor optical amplifiers than the prior art, and the size of the wavelength division multiplexer is smaller. Moreover, a semiconductor optical amplifier array specially made of group III-V semiconductor materials is used for optical amplification to realize the emission output of multi-wavelength optical signals, and an optical resonant cavity is formed by the semiconductor optical amplifiers. This can further reduce the device size, reduce the internal loss of the system, and increase the output laser power. Finally, it can realize the output of more multi-wavelength optical signals with a smaller number of semiconductor optical amplifiers, and has the advantages of a more compact device structure and higher integration.

[0048] Compared with the background technology, the present invention has the following beneficial effects:

[0049] 1. Based on the intracavity multi-wavelength semiconductor laser integrated on the same chip, the device size is small and the manufacturing cost is low.

[0050] 2. By using the dual-channel multiplexing output, more channels of wavelength output are realized with fewer semiconductor optical amplifiers. The device structure is more compact and the requirements for the driving circuit are lower.

[0051] 3. Each wavelength is provided with gain by two semiconductor optical amplifiers. By selecting different semiconductor optical amplifiers, the output wavelength can be controlled, and the intensity of each wavelength can be adjusted, which has great flexibility.

[0052] 4. Based on the intracavity laser, its output wavelength corresponds to the wavelength of the wavelength division multiplexer, and no additional wavelength control method is required.

[0053] Compared with the existing semiconductor multi-wavelength semiconductor lasers, the present invention has a more compact design method and realizes more channels of wavelength output with fewer semiconductor optical amplifiers. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic structural diagram of the system of the present invention.

[0055] Figure 2 It is a schematic diagram of the wavelength selection principle of a multi-wavelength semiconductor laser with a multi-lumen.

[0056] Figure 3 It is a schematic diagram of the wavelength selection principle of a multi-wavelength semiconductor laser with dual-channel multiplexed output.

[0057] Figure 4 It is a schematic structural diagram of a Y-branch beam combiner.

[0058] Figure 5 It is a schematic structural diagram of a multi-mode interference coupler beam combiner.

[0059] Figure 6 It is a schematic structural diagram of the chip of Embodiment 1 of the present invention.

[0060] Figure 7 It is a schematic structural diagram of the chip of Embodiment 2 of the present invention.

[0061] In the figure: input semiconductor optical amplifier array (1), wavelength division multiplexer (2), output semiconductor optical amplifier array (3), partial reflector (4), optical beam combiner (5), coupling lens (6), input waveguide (501), Y-branch beam combining region (502), output waveguide (503), multi-mode interference coupling region (504), tapered waveguide (505). Specific embodiments

[0062] The present invention will be further described below in conjunction with the accompanying drawings.

[0063] The schematic diagram of the basic composition structure of the present invention is as Figure 1 shown, mainly composed of an input semiconductor optical amplifier array 1, a wavelength division multiplexer 2, an output semiconductor optical amplifier array 3, two partial reflectors 4 and an optical beam combiner 5. The input semiconductor optical amplifier array 1 is connected to the input port of the wavelength division multiplexer 2. One end of the output semiconductor optical amplifier array 3 is connected to the output port of the wavelength division multiplexer 2, and the other end is connected to the optical beam combiner 5 through the partial reflector 4.

[0064] The input semiconductor optical amplifier array 1, the wavelength division multiplexer 2 and the output semiconductor optical amplifier array 3 form the laser light source part. Two optical signals with multiple wavelengths and different wavelength sequences are respectively output from the two output ends of the output semiconductor optical amplifier array 3, that is, the wavelengths of each optical signal in the two optical signals are different, and the wavelengths between the two optical signals are also different. The two optical signals emitted by the light source part are input to the optical beam combiner 5 through the two partial reflectors 4 for beam combination and then output.

[0065] Both the input semiconductor optical amplifier array 1 and the output semiconductor optical amplifier array 3 are constructed based on a specially prepared multi-channel semiconductor optical amplifier array structure.

[0066] The input semiconductor optical amplifier array 1 consists of N + 1 semiconductor optical amplifiers, and the output semiconductor optical amplifier array 3 consists of 2 semiconductor optical amplifiers. Semiconductor optical amplifiers are made of optically active materials and can convert injected electrons into photons through the stimulated emission process. Generally, semiconductor optical amplifiers can provide gain for light in a relatively large wavelength range, and the gain range can reach dozens of nanometers. The input semiconductor optical amplifier array 1 and the output semiconductor optical amplifier array 3 are made of the same semiconductor material and have the same gain range.

[0067] The wavelength division multiplexer 2 has N + 1 input ports and 2 output ports. For a wavelength division multiplexer, light of different wavelengths entering from one input port has different transmission losses when reaching one output port. Light of different wavelengths enters from different input ports, and the losses to one output port are as Figure 2 shown. There is a wavelength corresponding to the minimum transmission loss between each input port and output port, which is the working wavelength of this input-output port. The wavelength division multiplexer 2 can multiplex light signals of different wavelengths input from different input ports to one output port for output, achieving the effect of wavelength multiplexing.

[0068] The implementation method of the wavelength division multiplexer 2 can be an arrayed waveguide grating or an etched diffraction grating. The arrayed waveguide grating uses multiple arrayed waveguides of different lengths. Through the multi-beam interference process, light of different wavelengths is imaged at different positions to achieve the effect of wavelength multiplexing. The etched diffraction grating uses a grating to reflect and image light of different wavelengths at different positions to achieve the effect of wavelength multiplexing.

[0069] Both the input semiconductor optical amplifier array 1 and the output semiconductor optical amplifier array 3 adopt a multi-channel semiconductor optical amplifier array. The multi-channel semiconductor optical amplifier array is made of III-V semiconductor materials and is used to convert electrons into photons to provide optical gain, switching, and active laser functions. Other devices such as one wavelength division multiplexer 2, two partial reflectors 4, and one optical combiner 5, etc., except for the multi-channel semiconductor optical amplifier array, use passive materials such as silicon and silicon nitride. Such materials are used to achieve low-loss transmission of light. The two materials are integrated on the same chip through end-face coupling or vertical coupling, enabling the multi-wavelength optical transmitter-router of the present invention to be realized through hybrid integration technology.

[0070] The multi-channel semiconductor optical amplifier array is mainly made in the following way:

[0071] First, a wafer structure mainly composed of a substrate, a lower cladding layer, an active layer, and an upper cladding layer from bottom to top is fabricated. The refractive index of the active layer material is higher than that of the upper cladding layer and the lower cladding layer materials. The fabrication is achieved by using the method of shallow etched waveguides, and the fabrication process is as follows:

[0072] Then, the designed pattern is transferred to the surface of the upper cladding layer through photolithography, and the upper cladding layer is removed by wet etching or dry etching methods, so that the upper cladding layer forms a ridge waveguide. The substrate, the lower cladding layer, and the active layer are not etched and have the same size. Multiple ridge waveguides are directly fabricated according to the designed pattern, that is, the upper cladding layer is etched in multiple places, and etching grooves are formed at the etched places, and multiple strip-shaped structures are formed at the unetched places as ridge waveguides. Then, the lower cladding layer and the active layer between adjacent ridge waveguides are etched overetching to form deep etching grooves. Thus, each ridge waveguide of the upper cladding layer serves as a semiconductor optical amplifier, and deep etching grooves are provided to separate them between adjacent semiconductor optical amplifiers;

[0073] Next, a silicon oxide insulating layer is deposited on the upper cladding layer and the exposed active layer, and then a window is opened on the silicon oxide insulating layer and a P-type electrode connected to the upper cladding layer is fabricated. Finally, after the back surface of the substrate is thinned and polished, an N-type electrode connected to the substrate is fabricated on the back surface.

[0074] Each semiconductor optical amplifier in the multi-channel semiconductor optical amplifier array has the same waveguide length and is fabricated in an arrayed manner with the same spacing. An independent P-type electrode is fabricated on each semiconductor optical amplifier, and all semiconductor optical amplifiers use a common N-type electrode;

[0075] In this way, a current can be independently applied to the active layer of each semiconductor optical amplifier, and then the optical signal passing through the semiconductor optical amplifier can be amplified to provide an optical gain effect. Since the design and fabrication processes of each semiconductor optical amplifier are the same, their performances are similar, and the same optical amplification effect can be achieved. Moreover, deep etching grooves can be used to separate adjacent semiconductor optical amplifiers to reduce current crosstalk and thermal crosstalk.

[0076] When the current applied to the semiconductor optical amplifier is greater than the threshold current, the optical gain provided by the semiconductor optical amplifier in each resonant cavity is greater than the loss in the resonant cavity, and laser oscillation output can be achieved in this resonant cavity.

[0077] The lower cladding layer and the upper cladding layer adopt binary compound materials, such as InP for the binary compound materials. The upper cladding layer material is P-type doped, and the lower cladding layer material is N-type doped. The active layer adopts a multi-quantum well material composed of quaternary compound materials, such as InGaAsP for the quaternary compound materials. The refractive index of the active layer material is higher than that of the upper cladding layer and the lower cladding layer materials, so that light is confined to be transmitted in the active layer. After applying a current, the active layer material can convert electrons into photons to provide optical gain.

[0078] One end of the N + 1 semiconductor optical amplifiers in the input semiconductor optical amplifier array 1 is a high-reflection surface, and the other end is sequentially connected to the N + 1 input ports of the wavelength division multiplexer 2. One end of the 2 semiconductor optical amplifiers in the output semiconductor optical amplifier array 3 is sequentially connected to the 2 output ports of the wavelength division multiplexer 2, and the other end is connected to the partial reflector 4.

[0079] Specifically, there is a minimum loss wavelength corresponding to each input port and output port of the wavelength division multiplexer 2, and the wavelength multiplexing effect can be achieved. The implementation method can be an arrayed waveguide grating or an etched diffraction grating.

[0080] In specific implementation, the partial reflector 4 adopts structures such as deep etching grooves, etched end faces or cleaved end faces. The partial reflector 4 can reflect a part of the light in the input direction, and the other part of the light is transmitted and continues to be transmitted. The reflected light can be used to form a resonant cavity, and the transmitted light can be used as laser output.

[0081] The optical combiner 5 is an on-chip combiner device such as a Y-branch combiner or a multimode interference coupler.

[0082] More specifically, the Y-branch combiner includes an input waveguide 501, a Y-branch combining region 502, and an output waveguide 503. The two input waveguides 501 are respectively connected to both ends of the input side of the Y-branch combining region 502, and one end of the output side of the Y-branch combining region 502 and the output waveguide 503.

[0083] More specifically, the multimode interference coupler includes an input waveguide 501, an output waveguide 503, a multimode interference coupling region 504, and a tapered waveguide 505. The two input waveguides 501 are respectively connected to both ends of the input side of the multimode interference coupling region 504 through their respective tapered waveguides 505, and one end of the output side of the multimode interference coupling region 504 is connected to the output waveguide 503 through the tapered waveguide 505.

[0084] The optical combiner 5 combines two beams of light into one output. The lasers emitted by different output semiconductor optical amplifiers in the output semiconductor optical amplifier array 4 can be combined through the optical combiner 5 to achieve common output. The laser realizes the common output of 2N + 2 wavelengths.

[0085] An optical resonator is formed between the high-reflection surface end of one semiconductor optical amplifier in the input semiconductor optical amplifier array 1 and the partial reflector 4. The interior of this optical resonator includes one semiconductor optical amplifier in the output semiconductor optical amplifier array 1, one semiconductor optical amplifier in the output semiconductor optical amplifier array 3, and the wavelength division multiplexer 2. For this optical resonator, when currents are applied to the two semiconductor optical amplifiers, electrons are converted into photons. After the current magnitude reaches the threshold current, population inversion occurs in the optical resonator, achieving laser output. Since the wavelength division multiplexer 2 is inside the resonator, light of different wavelengths has different transmission losses inside the cavity. The light corresponding to the operating wavelength of the wavelength division multiplexer 2 at this input-output port has the minimum transmission loss, and its corresponding threshold current is the lowest, achieving laser lasing first. Due to the mode competition effect, light of other wavelengths is suppressed, enabling the laser to output only light of one wavelength, and this wavelength corresponds to the operating wavelength of the wavelength division multiplexer 2 between this input-output channel.

[0086] After currents are applied to all semiconductor optical amplifiers in the input semiconductor optical amplifier array 1 and the output semiconductor optical amplifier array 3, a total of 2N + 2 resonant cavities are formed in the multi-wavelength semiconductor laser, and light signals of 2N + 2 wavelengths can be excited in total. Since different resonant cavities correspond to different input-output port combinations of the wavelength division multiplexer 2, these 2N + 2 wavelengths correspond to the wavelengths with the minimum loss between the input-output ports of the wavelength division multiplexer 2. The multi-wavelength semiconductor laser can achieve the output of up to 2N + 2 different wavelengths of light, and among them, there are N + 1 wavelengths of laser output in each output semiconductor optical amplifier.

[0087] In general application scenarios, it is required that the output wavelengths of the multi-wavelength semiconductor laser are continuous and have equal wavelength intervals. To meet this requirement, the wavelengths λ corresponding to the minimum loss between the input-output ports of the wavelength division multiplexer 2 should be designed and optimized accordingly.

[0088] Define the wavelength corresponding to the minimum loss between the i-th input port and the j-th output port as λ i,j , where i = 1, 2, … N + 1 represents the input port number, and j = 1, 2 represents the output port number. To satisfy the final output wavelength interval of Δλ, design the positions of the input-output ports so that each wavelength satisfies:

[0089] λ (i+1,j) - λ (i,j) = 2Δλ

[0090] λ (i,j+1) - λ (i,j) = 3Δλ

[0091] In this way, for the two output ports, the superposition effect of their transmission spectra for different input channels is as Figure 3 shown. Except for λ1,1 and λ N+1,2 Except for these two wavelengths and λ, the interval between the other 2N wavelengths is Δλ. Therefore, the present invention can achieve the output of 2N continuous wavelengths with a wavelength interval of Δλ.

[0092] In the above design method, the wavelength interval of the output ports is set to 3Δλ, that is, λ (i,j+1) - λ (i,j) = 3Δλ, which makes the two edge output wavelengths discontinuous with the other 2N wavelengths. This design is to reduce the required size of the wavelength division multiplexer 2. In the present invention, the wavelength setting interval of the corresponding channels between the input ports of the wavelength division multiplexer 2 is 2Δλ, and the wavelength interval of the corresponding channels between the output ports of the wavelength division multiplexer 2 is 3Δλ. For common wavelength division multiplexers, such as arrayed waveguide gratings or etched diffraction gratings, the smaller the wavelength interval between adjacent ports, the smaller the overall size of the device. In the present invention, the size of the wavelength division multiplexer 2 only needs to meet the light splitting ability for the 2Δλ wavelength interval, and the multi-wavelength laser output with a wavelength interval of Δλ can be achieved. Therefore, the whole device has a smaller size, which is beneficial to realizing a multi-wavelength semiconductor laser with more output wavelengths.

[0093] In the present invention, a total of N + 3 semiconductor optical amplifiers are used to achieve the output of 2N continuously spaced wavelengths. The design method using dual-channel multiplexing effectively reduces the number of required semiconductor optical amplifiers, which is also beneficial to realizing a multi-wavelength semiconductor laser with more output wavelengths.

[0094] Two semiconductor optical amplifiers in the output semiconductor optical amplifier array each output optical signals of N + 1 wavelengths. In the application, it is necessary to combine the two optical signals into one output through the optical combiner 5. According to different implementation methods of the optical combiner, the present invention is divided into the following two embodiments. Embodiment 1:

[0095] In Embodiment 1 of the present invention, each part in the semiconductor multi-wavelength semiconductor laser is integrated on the same chip. The partial reflector 4 is realized on the chip through a deep etching groove, and the combiner 5 is realized on the chip through a Y-branch combiner, a multimode interference coupler, etc.

[0096] Figure 4 Fig. is a schematic structural diagram of the composition of the Y-branch combiner scheme for the combiner 5. The Y-branch combiner is composed of an input waveguide 501, a coupling region 502, and an output waveguide 503. The input waveguide 501 is composed of two symmetrically arranged waveguides up and down. The light entering from one of the waveguides is coupled into the output waveguide 503 through the coupling region 502, thus realizing the function of combining the light from two waveguides into one waveguide.

[0097] Figure 5It is a schematic structural diagram of the composition of the optical combiner 5 using the multimode interference coupler scheme. The multimode interference coupler is composed of an input waveguide 501, a multimode interference region 504, and an output waveguide 503. Among them, the input waveguide 501 is composed of two vertically symmetric waveguides. The light entering from one waveguide interferes and forms an image in the multimode interference region, and then is coupled into the output waveguide, which can also achieve the function of combining light from two waveguides into one waveguide. Preferably, in order to reduce the coupling loss, tapered waveguides 505 can be introduced between the input waveguide 501 and the multimode interference region 504, and between the multimode interference region 502 and the output waveguide 503 to realize the mode conversion process.

[0098] The chip design scheme of Embodiment 1 is as Figure 6 shown. In the example, the wavelength division multiplexer 2 uses an etched diffraction grating, and the optical combiner 5 uses a Y-branch combiner. Each part of the semiconductor multi-wavelength semiconductor laser is integrated on the same chip. Among them, the input semiconductor optical amplifier array 1 and the output semiconductor optical amplifier array 3 are fabricated on an active semiconductor material that can provide optical gain. The wavelength division multiplexer 2, the partial reflector 4, and the optical combiner 5 are fabricated on a passive semiconductor material with lower optical loss. The active material and the passive material can be integrated on the same substrate by means of monolithic integration or heterogeneous integration. This embodiment has the most compact structure and the smallest device size. Embodiment 2:

[0099] Since the on-chip optical combiner generally has a loss of 3 dB, in order to reduce the loss, the combiner 5 in Embodiment 2 uses an optical fiber combiner.

[0100] In Embodiment 2 of the present invention, the input semiconductor optical amplifier array 1, the wavelength division multiplexer 2, the output semiconductor optical amplifier array 3, and the partial reflector 4 are integrated on the same chip by means of monolithic integration or heterogeneous integration. The partial reflector 4 is realized by etching the end face or cleaving the end face. The combiner 5 is an optical fiber combiner. The design scheme of Embodiment 2 of the present invention is as Figure 7 shown. In order to achieve low-loss coupling between the chip and the optical fiber combiner, a coupling lens 6 is added between the partial reflector 4 and the combiner 5. Using an optical fiber combiner in Embodiment 2 increases the complexity of the device, but the optical fiber combiner has lower loss and can achieve better laser output quality.

[0101] Comparative example:

[0102] In Patent CN201310230999.4 and Patent CN116683291A, wavelength selection is achieved by fabricating a grating on the active layer to realize multi-wavelength output. Compared with the above comparative examples, the present invention realizes multi-wavelength output by combining a specially prepared multi-channel semiconductor optical amplifier array and a wavelength division multiplexer. The required manufacturing process is simple, only requiring one etching process and not requiring a high-precision grating manufacturing process (the grating manufacturing requires an accuracy of the order of nanometers, while the manufacturing of each device in the present invention only requires an accuracy of the order of micrometers), and does not require regrowth of the upper cladding, resulting in low requirements for manufacturing equipment and low manufacturing costs.

[0103] In Patent CN201410613588, multi-wavelength output is achieved by integrating a semiconductor optical amplifier, a phase modulator, an arrayed waveguide grating, etc. The semiconductor optical amplifier used therein is fabricated by etching the ohmic contact layer. The present invention uses a specially prepared multi-channel semiconductor optical amplifier array, and each semiconductor optical amplifier is fabricated by etching the upper cladding. The input current is restricted to enter the active layer in a specific area, which can reduce the crosstalk between semiconductor optical amplifiers and improve the optical amplification efficiency. The wavelength division multiplexer used therein has only one output port. To achieve 2N output wavelengths, 2N semiconductor optical amplifiers are required. The present invention adopts a wavelength division multiplexer with dual-channel multiplexing output, and only N + 3 semiconductor optical amplifiers are needed to achieve 2N output wavelengths.

[0104] The above specific embodiments are used to explain the present invention rather than limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims of the present invention fall within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. Therefore, any equivalent changes or modifications made according to the structure, features, and principles described in the scope of the present invention patent application are included in the scope of the present invention patent application.

Claims

1. A multi-wavelength semiconductor laser based on dual-channel multiplexing output, characterized in that: The laser light source device comprises an input semiconductor optical amplifier array (1), a wavelength division multiplexer (2), an output semiconductor optical amplifier array (3), two partial reflectors (4) and an optical combiner (5); the input semiconductor optical amplifier array (1), the wavelength division multiplexer (2) and the output semiconductor optical amplifier array (3) constitute a laser light source part; two optical signals with multiple wavelengths and different wavelength sequences are respectively emitted from two output ends of the output semiconductor optical amplifier array (3) as output light of the laser light source part; the two optical signals are respectively input into the two partial reflectors (4) and then input into the optical combiner (5) together for beam combining and output; The input semiconductor optical amplifier array (1) and the output semiconductor optical amplifier array (3) are both constructed based on a multi-channel semiconductor optical amplifier array structure; The wavelength division multiplexer (2) has N+1 input ports and 2 output ports, and the 2 output ports are respectively connected to the 2 output ports of the output semiconductor optical amplifier array (3); An optical signal sequence consisting of N+1 optical signals with working wavelengths spaced at intervals of 2Δλ, wherein the N+1 optical signals of the optical signal sequence are respectively output from an input semiconductor optical amplifier array (1) and respectively input into an output port of the wavelength division multiplexer after passing through the N+1 input ports of the wavelength division multiplexer; The optical signal sequences received by the two output ports of the wavelength division multiplexer are separated by a working wavelength of 3Δλ; The input semiconductor optical amplifier array has N+1 semiconductor optical amplifiers connected to the input port of the wavelength division multiplexer, and the output semiconductor optical amplifier array has 2 semiconductor optical amplifiers connected to the output port of the wavelength division multiplexer; The input semiconductor optical amplifier array (1), the wavelength division multiplexer (2) and the output semiconductor optical amplifier array (3) form a total of 2N+2 optical resonant cavities. By applying current to the semiconductor optical amplifiers in the input semiconductor optical amplifier array (1) and the output semiconductor optical amplifier array (3) to provide optical gain, a total of 2N+2 wavelengths of laser light are excited, and the output wavelength corresponds to the operating wavelength between each input-output port of the wavelength division multiplexer (2), wherein the wavelength interval between the 2N wavelengths is Δλ.

2. A multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 1, characterized in that: The output semiconductor optical amplifier array (3) is connected to the optical combiner (5) via a partial reflector (4); the partial reflector (4) reflects a portion of the optical signal to achieve laser resonance, and transmits another portion of the optical signal to the optical combiner (5) to achieve laser output.

3. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 1, characterized in that: The input semiconductor optical amplifier array (1) and the output semiconductor optical amplifier array (3) are both multi-channel semiconductor optical amplifier arrays.

4. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 3, characterized in that: The multi-channel semiconductor optical amplifier array is made of III-V semiconductor materials, and other devices except the multi-channel semiconductor optical amplifier array are made of passive materials such as silicon and silicon nitride.

5. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 3, characterized in that: The multi-channel semiconductor optical amplifier array is mainly manufactured in the following manner: First, a wafer structure is prepared which is mainly composed of a substrate, a lower cladding layer, an active layer and an upper cladding layer in order from bottom to top, wherein the refractive index of the active layer material is higher than the refractive index of the upper cladding layer and the lower cladding layer material; Then, the design pattern is transferred to the surface of the upper cladding layer by photolithography, and the upper cladding layer is removed by wet etching or dry etching to form a ridge waveguide in the upper cladding layer, and a plurality of ridge waveguides are directly prepared according to the design pattern, and then the lower cladding layer and the active layer between adjacent ridge waveguides are etched to form deep etched grooves; thereby, each ridge waveguide of the upper cladding layer is used as a semiconductor optical amplifier, and deep etched grooves are set between adjacent semiconductor optical amplifiers to separate them; Next, a silicon oxide insulating layer is deposited on the upper cladding layer and the exposed active layer. A window is then opened in the silicon oxide insulating layer and a P-type electrode connected to the upper cladding layer is made. Finally, an N-type electrode connected to the substrate is made after thinning and polishing the back side of the substrate.

6. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 5, characterized in that: Each semiconductor optical amplifier has the same waveguide length and is manufactured in an array manner with the same spacing. An independent P-type electrode is manufactured on each semiconductor optical amplifier, and all semiconductor optical amplifiers use a common N-type electrode. A current is independently applied to each semiconductor optical amplifier, thereby providing optical gain and switching action to the optical signal passing through the semiconductor optical amplifier; When the current applied to the semiconductor optical amplifier is greater than the threshold current, the optical gain provided by the semiconductor optical amplifier in each optical resonant cavity is greater than the loss in the optical resonant cavity, and laser lasing output is achieved in the optical resonant cavity; When the current applied to the semiconductor optical amplifier is less than or equal to the threshold current, the optical gain provided by the semiconductor optical amplifier in each optical resonant cavity is less than the loss in the optical resonant cavity, and the optical resonant cavity absorbs the input optical signal and does not output the optical signal.

7. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 5, characterized in that: The lower cladding layer and the upper cladding layer are made of binary compound materials, wherein the upper cladding layer material is P-type doped and the lower cladding layer material is N-type doped; the active layer is made of a multi-quantum well material composed of a quaternary compound material.

8. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 1, characterized in that: The input semiconductor optical amplifier array (1), the wavelength division multiplexer (2), the output semiconductor optical amplifier array (3), the partial reflector (4) and the optical beam combiner (5) are integrated on the same chip by means of monolithic integration or hybrid integration.

9. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 8, characterized in that: The optical beam combiner (5) is a fiber beam combiner, and a coupling lens (6) is provided at the output end of the fiber beam combiner, and is coupled with the chip through the coupling lens (6) to achieve laser beam combining output.

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