Multi-wavelength semiconductor laser based on dual-channel multiplexing output

Abstract

The invention discloses a multi-wavelength semiconductor laser based on dual-channel multiplexing output. Mainly comprises N + 1 input semiconductor optical amplifiers, a wavelength division multiplexer, two output semiconductor optical amplifiers and a light beam combiner, and the input semiconductor optical amplifiers, the wavelength division multiplexer and the output semiconductor optical amplifiers jointly form an optical resonant cavity to excite laser with corresponding wavelengths. Light emitted by the two output semiconductor optical amplifiers is output together after passing through a light beam combiner; by designing the working wavelength interval of the input and output ports of the wavelength division multiplexer, multi-wavelength simultaneous output of 2N continuous wavelengths is realized. Compared with an existing multi-wavelength semiconductor laser, the multi-wavelength semiconductor laser has the advantages that the design mode is more compact, and output of more wavelengths is achieved through fewer semiconductor optical amplifiers.

Description

Technical Field

[0001] The invention relates to a multi-wavelength semiconductor laser, in particular to a multi-wavelength semiconductor laser based on dual-channel multiplexing output. Background Art

[0002] A multi-wavelength semiconductor laser is a laser that can output multiple wavelength laser signals at the same time. It has a wide range of applications in optical communications, optical sensing, optical computing and other fields. In wavelength division multiplexing passive optical networks (WDM-PON), multi-wavelength semiconductor lasers are often used as central node light sources. By uploading and downloading light of different wavelengths at each node, each wavelength is reused, reducing the demand for lasers at each node and effectively reducing the cost of the system. Multi-wavelength semiconductor lasers are also commonly used in optical sensing. Using multiple wavelengths for joint detection can improve the sensing range and accuracy. In the field of optical computing, using multi-wavelength semiconductor lasers as light sources can independently process computing data at each wavelength, giving full play to the parallel computing capabilities of the optical platform. For multi-wavelength semiconductor lasers, the current main research direction is to reduce the cost of laser manufacturing, increase the number of output wavelengths, and improve the output laser quality.

[0003] Traditional multi-wavelength semiconductor lasers are based on fiber lasers. The nonlinear effect of optical fiber can be used to expand single-wavelength lasers to multi-wavelength outputs. Currently, such lasers can already output more than one hundred wavelengths of light, but fiber lasers are large in size, high in cost, and have poor wavelength uniformity. Another way to achieve this is a semiconductor laser array, which uses multiple single-wavelength lasers to form an array. The final output light is combined into a beam after passing through a fiber combiner. The multi-wavelength semiconductor laser composed in this way has a compact structure, and its output performance is the same as that of a single-wavelength laser, and each wavelength of light can be controlled individually, which has higher flexibility. However, since its output is formed by combining multiple lasers, an N-way multi-wavelength semiconductor laser requires an N×1 fiber combiner, which increases the complexity and cost of the system.

[0004] Based on the principle of intracavity mode selection, multi-wavelength semiconductor lasers can also be constructed. The semiconductor optical amplifier array and the wavelength division multiplexer are integrated together. The wavelength division multiplexer and different semiconductor optical amplifiers form a resonant cavity, and the lasing wavelength corresponds to the wavelength with the smallest loss of the wavelength division multiplexer. In this way, multiple semiconductor optical amplifiers work at the same time, and multiple wavelengths can be output simultaneously. Such lasers also have the advantages of small size and low cost of semiconductor lasers, and all wavelengths are output from one port, without the need for a fiber combiner. However, for such multi-wavelength semiconductor lasers, as the number of wavelengths increases, more semiconductor optical amplifiers are needed, and the size of the integrated wavelength division multiplexer also increases, 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] In view of the shortcomings of the prior art, an object of the present invention is to provide a semiconductor multi-wavelength semiconductor laser that can achieve laser output with more wavelengths using fewer semiconductor optical amplifiers.

[0006] The present invention can realize multi-wavelength simultaneous output of 2N continuous wavelengths by designing the wavelength interval of the input and output ports of the wavelength division multiplexer, and has a smaller and more compact structure and stronger functions.

[0007] The technical solution adopted by the present invention is: The optical amplifier array is mainly composed of an input semiconductor optical amplifier array, a wavelength division multiplexer, an output semiconductor optical amplifier array, two partial reflectors and an optical combiner. 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 optical combiner through the partial reflector.

[0008] The input semiconductor optical amplifier array, wavelength division multiplexer and output semiconductor optical amplifier array constitute 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 beam combining and are divided into two optical signals with multiple wavelengths and different wavelength sequences. The two optical signals are respectively input into the two ports of the output semiconductor optical amplifier array with two channels. After the optical amplification of the output semiconductor optical amplifier array, the two output ends of the output semiconductor optical amplifier array emit them respectively. Two optical signals with multiple wavelengths and different wavelength sequences are respectively 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 optical beam combiner together for beam combining and output. The input semiconductor optical amplifier array and the output semiconductor optical amplifier array are both constructed based on a multi-channel semiconductor optical amplifier array structure.

[0009] The optical gain is provided by the input semiconductor optical amplifier array and the output semiconductor optical amplifier array, the wavelength multiplexer selects the output wavelength, and the optical combiner realizes the simultaneous output of multiple wavelengths.

[0010] The wavelength division multiplexer has N+1 input ports, the N+1 input ports are respectively connected to the N+1 output ports of the input semiconductor optical amplifier array, and the wavelength division multiplexer has 2 output ports, the 2 output ports are respectively connected to the 2 output ports of the output semiconductor optical amplifier array; for the wavelength division multiplexer, light of different wavelengths has different transmission losses when transmitted from an input port to an output port, and one wavelength of light has the smallest transmission loss, corresponding to the working wavelength between the input and output ports.

[0011] An optical signal sequence is composed 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 and respectively input into the same 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 differ in working wavelengths spaced at intervals of 3Δλ, that is, the working wavelengths of the optical signal sequence output from one of the output ports are λ1, λ2, ..., λ N+1 , where the interval between adjacent working wavelengths is 2Δλ, then the working wavelengths of the optical signal sequence output by an output port are λ1+3Δλ, λ2+3Δλ, …, λ N+1 .

[0012] For the same output port of the wavelength division multiplexer, N+1 input ports correspond to N+1 working wavelengths, and there is an equal interval between two adjacent working wavelengths in the wavelength sequence composed of the N+1 working wavelengths, and the interval is 2Δλ, where Δλ represents the wavelength difference between adjacent wavelengths output by the multi-wavelength laser; For the same input port of the wavelength division multiplexer, the two output ports correspond to two working wavelengths.

[0013] There are 2N+2 working wavelengths corresponding to the input and output ports of the wavelength division multiplexer, among which 2N wavelengths have the same wavelength interval Δλ and can be used as the output of the laser.

[0014] The input semiconductor optical amplifier array outputs two optical signals with a wavelength interval of 2Δλ at each output port and inputs them into an input port of the wavelength division multiplexer, and the wavelengths of the two optical signals outputted from each output port of the input semiconductor optical amplifier array are different; After wavelength division multiplexing, the wavelength division multiplexer outputs two optical signal sequences at each output port. After the output semiconductor optical amplifier gain, they enter the corresponding partial reflectors. Each optical signal sequence contains N+1 optical signals of different working wavelengths with a wavelength interval of 2Δλ. The wavelengths of all 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 by the two partial reflectors into an optical signal sequence consisting of 2N+2 optical signals of different working wavelengths, among which 2N working wavelengths have equal intervals, and the interval is Δλ. The other two working wavelengths are the minimum and maximum values ​​of all working wavelengths, respectively, and differ from the second minimum and second maximum values ​​of all working wavelengths by 2Δλ respectively.

[0015] Each partial reflector outputs the same optical signal sequence as that transmitted by the wavelength division multiplexer to the optical combiner, and the optical combiner combines the two optical signal sequences transmitted by the two partial reflectors into an optical signal sequence consisting of 2N+2 optical signals with a wavelength interval of Δλ.

[0016] 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 wavelength division multiplexer has N+1 input ports and 2 output ports.

[0017] The input semiconductor optical amplifier array, the wavelength division multiplexer and the output semiconductor optical amplifier array constitute a total of 2N+2 optical resonant cavities. 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 light are excited. The output wavelength corresponds to the operating wavelength between each input-output port of the wavelength division multiplexer, wherein the wavelength interval between the 2N wavelengths is Δλ.

[0018] A semiconductor optical amplifier in the input semiconductor optical amplifier array, a semiconductor optical amplifier in the output semiconductor optical amplifier array and the wavelength division multiplexer form an optical resonant cavity. For the optical resonant cavity, each wavelength of light has different transmission losses, wherein the wavelength division multiplexer has the smallest loss at the operating wavelength between the input-output channels. When current is applied to the input semiconductor optical amplifier, the light of this wavelength has the lowest threshold current in the resonant cavity, and the laser signal of the corresponding wavelength can be excited in the resonant cavity.

[0019] By designing the corresponding working wavelength intervals between different input and output ports of the wavelength division multiplexer, 2N wavelengths of the final output 2N+2 wavelengths can have the same wavelength interval Δλ. The specific design method is that the working wavelength interval of the corresponding channels between each input port of the wavelength division multiplexer is 2Δλ, and the working wavelength interval of the corresponding channels between each output port of the wavelength division multiplexer is 3Δλ.

[0020] The wavelength division multiplexer is an etched diffraction grating or an arrayed waveguide grating.

[0021] The output semiconductor optical amplifier array is connected to the optical combiner through a partial reflector. The partial reflector reflects a part of the light signal incident from the semiconductor optical amplifier of the output semiconductor optical amplifier array to realize laser resonance, and transmits another part of the light signal to the optical combiner to realize laser output.

[0022] The input semiconductor optical amplifier array and the output semiconductor optical amplifier array are both multi-channel semiconductor optical amplifier arrays.

[0023] 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 III-V semiconductor materials set by the present invention, and cannot adopt conventional semiconductor optical amplifiers for array arrangement. The situation is that the input semiconductor optical amplifier array and the output semiconductor optical amplifier array are to be connected to the input and output ports of the wavelength division multiplexer respectively. The multi-channel semiconductor optical amplifier array designed by the present invention can greatly reduce the spacing between semiconductor lasers, minimize the size of each part, and improve the overall integration. The reduction in the size of each part reduces the overall loss of the system and increases the output power of the laser.

[0024] 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 manufactured once, the manufacturing process is simple, the performance is the same, and a uniform multi-wavelength output effect can be achieved.

[0025] The multi-channel semiconductor optical amplifier array is made of III-V semiconductor materials. In addition to the multi-channel semiconductor optical amplifier array, other devices such as a wavelength division multiplexer, two partial reflectors and an optical combiner are made of passive materials such as silicon and silicon nitride. Such materials are used to achieve low-loss transmission of light.

[0026] 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.

[0027] Voltage / current is applied to the P-type electrode and N-type electrode of each semiconductor optical amplifier to convert photons in the active layer to achieve optical gain.

[0028] 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 effects 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, and finally outputted from the semiconductor optical amplifier of the output semiconductor optical amplifier array; 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 an optical signal.

[0029] 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.

[0030] In the multi-wavelength semiconductor laser of the present invention, each semiconductor optical amplifier is made of active materials that provide optical gain and optical amplification functions, and the wavelength division multiplexer, two partial reflectors, and an optical combiner are made of passive materials with low optical loss. Each part can be integrated on the same chip through monolithic integration technology or hybrid integration technology to minimize the size.

[0031] In monolithic integration technology, all parts of the device are made on the same Group III-V semiconductor material, among which the active layer of the semiconductor optical amplifier part is quantum well material. After the materials for making other parts undergo processes such as quantum well intermixing, docking regrowth, and biased quantum well, their quantum well energy bands change, and the absorption of light at the working wavelength decreases, turning them into passive materials.

[0032] In hybrid integration technology, the semiconductor optical amplifier is partially made on III-V semiconductor materials, and the other parts are made on silicon-based materials such as silicon on insulator (SOI) and silicon nitride, which can achieve low-loss transmission of light. The two materials are integrated into the same chip through end-face coupling or vertical coupling, achieving high integration.

[0033] In the first embodiment, all parts of the semiconductor multi-wavelength semiconductor laser are integrated on the same chip. The partial reflector is implemented on the chip by deep etching grooves, and the beam combiner can be implemented on the chip by Y-branch beam combiner, multimode interference coupler, etc. The input semiconductor optical amplifier array and the output semiconductor optical amplifier array are made on active materials that can provide optical gain, and the wavelength division multiplexer, partial reflector and optical beam combiner are made on passive materials with lower optical loss. The active material and the passive material can be integrated on the same substrate by monolithic integration or heterogeneous integration.

[0034] In a 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 by monolithic integration or heterogeneous integration, and the partial reflector is realized by etching the end face or cleaving the end face. The beam combiner is a fiber beam combiner, which realizes beam combining output after coupling with the partial reflector through a coupling lens.

[0035] The input semiconductor optical amplifier array, the wavelength division multiplexer, the output semiconductor optical amplifier array, the partial reflector and the optical beam combiner are integrated on the same chip in a monolithic integration or hybrid integration manner.

[0036] 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. In addition to the multi-channel semiconductor optical amplifier array, other devices such as a wavelength division multiplexer, two partial reflectors and an optical combiner 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, so that the multi-wavelength optical transmitter-router of the present invention is realized through hybrid integration technology.

[0037] The optical beam combiner is a fiber beam combiner, and a coupling lens is arranged at the output end of the fiber beam combiner, which is coupled with the chip through the coupling lens to realize laser beam combining output.

[0038] The innovation of the present invention lies in that the multi-wavelength optical signals output from the two output channels of the same wavelength division multiplexer are combined and output by dual-channel multiplexing output. In this way, when the same number of wavelengths are output, the present invention requires fewer semiconductor optical amplifiers than the prior art, and the size of the wavelength division multiplexer is smaller. In addition, a semiconductor optical amplifier array specially made of III-V semiconductor materials is used for optical amplification to realize the emission output of multi-wavelength optical signals. The optical resonant cavity is formed by semiconductor optical amplifiers, which can further reduce the size of the device, reduce the loss in the system, and increase the output laser power. Finally, a smaller number of semiconductor optical amplifiers can be used to achieve the output of more wavelength optical signals, and the device structure is more compact and the integration is higher.

[0039] Compared with the background technology, the present invention has the following beneficial effects: 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.

[0040] 2. By utilizing dual-channel multiplexed output, more wavelength outputs can be achieved with fewer semiconductor optical amplifiers, the device structure is more compact, and the requirements for the driving circuit are lower.

[0041] 3. Each wavelength is provided with gain by two semiconductor optical amplifiers. The output wavelength can be controlled by selecting different semiconductor optical amplifiers. The intensity of each wavelength can be adjusted, which has great flexibility.

[0042] 4. Based on intracavity laser, its output wavelength corresponds to the wavelength of wavelength division multiplexer, and no additional wavelength control method is required.

[0043] Compared with the existing semiconductor multi-wavelength semiconductor laser, the present invention has a more compact design and realizes the output of more wavelengths by using fewer semiconductor optical amplifiers. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the structure of the system of the present invention.

[0045] Figure 2 Schematic diagram of the wavelength selection principle of intracavity multi-wavelength semiconductor laser.

[0046] Figure 3 Schematic diagram of the wavelength selection principle of a multi-wavelength semiconductor laser with dual-channel multiplexed output.

[0047] Figure 4 Schematic diagram of the structure of the Y-branch combiner.

[0048] Figure 5 Schematic diagram of the structure of a multimode interference coupler combiner.

[0049] Figure 6 This is a schematic diagram of the chip structure of Example 1 of the present invention.

[0050] Figure 7 This is a schematic diagram of the chip structure of Example 2 of the present invention.

[0051] 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), multimode interference coupling region (504), tapered gradient waveguide (505). DETAILED DESCRIPTION

[0052] The present invention will be further described below in conjunction with the accompanying drawings.

[0053] The basic structural diagram of the present invention is as follows Figure 1 As shown, it is 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 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 combiner 5 through the partial reflector 4.

[0054] The input semiconductor optical amplifier array 1, the wavelength division multiplexer 2 and the output semiconductor optical amplifier array 3 constitute the laser light source part. Two optical signals with multiple wavelengths and different wavelength sequences are output from the two output ends of the output semiconductor optical amplifier array 3 respectively, that is, the wavelength of each optical signal in the two optical signals is different, and the wavelengths of the two optical signals are also different. The two optical signals emitted by the light source part are input into the optical combiner 5 through two partial reflectors 4 for beam combining and then output.

[0055] The input semiconductor optical amplifier array 1 and the output semiconductor optical amplifier array 3 are both constructed based on a specially prepared multi-channel semiconductor optical amplifier array structure.

[0056] The input semiconductor optical amplifier array 1 is composed of N+1 semiconductor optical amplifiers, and the output semiconductor optical amplifier array 3 is composed of 2 semiconductor optical amplifiers. The semiconductor optical amplifier is made of optically active materials and can convert injected electrons into photons through the stimulated emission process. Semiconductor optical amplifiers can generally provide gain for light in a larger wavelength range, and the gain range can reach tens 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.

[0057] WDM 2 has N+1 input ports and 2 output ports. For WDM, light of different wavelengths entering from an input port has different transmission losses after reaching an output port. The loss of light of different wavelengths entering from different input ports to an output port is as follows: Figure 2 As shown. There is a wavelength with minimum transmission loss between each input port and output port, which is the working wavelength of the input and output port. The wavelength division multiplexer 2 can combine different wavelength optical signals input from different input ports to one output port for output, thereby achieving wavelength multiplexing effect.

[0058] The implementation 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 to image light of different wavelengths at different positions through a multi-beam interference process to achieve a wavelength multiplexing effect. The etched diffraction grating uses a grating to reflect light of different wavelengths and image them at different positions to achieve a wavelength multiplexing effect.

[0059] The input semiconductor optical amplifier array 1 and the output semiconductor optical amplifier array 3 are both multi-channel semiconductor optical amplifier arrays, which are made of III-V semiconductor materials and are used to convert electrons into photons to provide optical gain, switching and active laser functions. In addition to the multi-channel semiconductor optical amplifier array, other devices such as a wavelength division multiplexer 2, two partial reflectors 4 and an optical combiner 5 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, so that the multi-wavelength optical transmitter-router of the present invention is realized through hybrid integration technology.

[0060] The multi-channel semiconductor optical amplifier array is mainly made in the following ways: First, a wafer structure is made, which is mainly composed of a substrate, a lower cladding, an active layer and an upper cladding from bottom to top. The refractive index of the active layer material is higher than that of the upper cladding and the lower cladding materials. The manufacturing process is as follows: 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, so that the upper cladding layer forms a ridge waveguide, and the substrate, the lower cladding layer, and the active layer remain unetched and have the same size, and a plurality of ridge waveguides are directly prepared and formed according to the design pattern, that is, the upper cladding layer is etched at multiple locations, and etching grooves are formed at the etched locations, and a plurality of strip structures are formed at the unetched locations as ridge waveguides, and then the lower cladding layer and the active layer between adjacent ridge waveguides are overetched to form deep etching grooves; thereby, the ridge waveguide of each upper cladding layer is used as a semiconductor optical amplifier, and deep etching 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, the back side of the substrate is thinned and polished, and an N-type electrode connected to the substrate is made on the back side.

[0061] Each semiconductor optical amplifier in the multi-channel semiconductor optical amplifier array 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. In this way, current can be applied independently to the active layer of each semiconductor optical amplifier, thereby amplifying the optical signal passing through the semiconductor optical amplifier to provide optical gain. Since the design and manufacturing process of each semiconductor optical amplifier are the same, their performance is similar and the same optical amplification effect can be achieved. In addition, deep etched grooves can be used to separate adjacent semiconductor optical amplifiers to reduce current crosstalk and thermal crosstalk.

[0062] 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 lasing output can be achieved in the resonant cavity.

[0063] The lower cladding and upper cladding are made of binary compound materials, such as InP, where the upper cladding material is P-type doped and the lower cladding material is N-type doped; the active layer is made of multi-quantum well materials composed of quaternary compound materials, such as InGaAsP, and the refractive index of the active layer material is higher than that of the upper and lower cladding materials, so that light is confined to the active layer for transmission. After applying current, the active layer material can convert electrons into photons to provide optical gain.

[0064] 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 connected in sequence to the N+1 input ports of the wavelength division multiplexer 2. One end of the two semiconductor optical amplifiers in the output semiconductor optical amplifier array 3 is connected in sequence to the two output ports of the wavelength division multiplexer 2, and the other end is connected to the partial reflector 4.

[0065] Specifically, each input port and output port of the wavelength division multiplexer 2 corresponds to a minimum loss wavelength, so that the wavelength multiplexing effect can be achieved. The implementation method can be an arrayed waveguide grating or an etched diffraction grating.

[0066] In a specific implementation, the partial reflector 4 adopts a structure such as a deep etched groove, an etched end face or a cleaved end face, and the partial reflector 4 can reflect a part of the light in the input direction, and transmit the other part of the light to continue to transmit. The reflected light can be used to form a resonant cavity, and the transmitted light can be output as a laser.

[0067] The optical combiner 5 is an on-chip beam combiner such as a Y-branch beam combiner or a multi-mode interference coupler.

[0068] More specifically, the Y-branch combiner includes an input waveguide 501, a Y-branch combining region 502 and an output waveguide 503, wherein 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 is connected to the output waveguide 503.

[0069] More specifically, the multimode interference coupler includes an input waveguide 501, an output waveguide 503, a multimode interference coupling region 504 and a tapered gradient waveguide 505. The two input waveguides 501 are connected to the input sides of the multimode interference coupling region 504 through their respective tapered gradient waveguides 505, and one end of the output side of the multimode interference coupling region 504 is connected through the tapered gradient waveguide 505 and the output waveguide 503.

[0070] The optical combiner 5 combines the two paths of light into one path for output. The lasers emitted by different output semiconductor optical amplifiers in the output semiconductor optical amplifier array 4 can be output together after being combined by the optical combiner 5, so that the laser can output 2N+2 wavelengths together.

[0071] An optical resonant cavity is formed between the high-reflection surface end of a semiconductor optical amplifier in the input semiconductor optical amplifier array 1 and the partial reflector 4. The optical resonant cavity includes a semiconductor optical amplifier in the output semiconductor optical amplifier array 1, a semiconductor optical amplifier in the output semiconductor optical amplifier array 3, and a wavelength division multiplexer 2. For the optical resonant cavity, when current is applied to the two semiconductor optical amplifiers, electrons are converted into photons. After the current reaches the threshold current, the number of particles in the optical resonant cavity is reversed, and laser output is achieved. Since the wavelength division multiplexer 2 is in the resonant cavity, light of different wavelengths has different transmission losses in the cavity. The light corresponding to the working wavelength of the wavelength division multiplexer 2 at the input and output port has the smallest transmission loss, and its corresponding threshold current is the lowest, and laser lasing is achieved first. Due to the mode competition effect, light of other wavelengths is suppressed, so that only one wavelength of light can be output by the laser, and this wavelength corresponds to the working wavelength of the wavelength division multiplexer 2 between the input and output channels.

[0072] After current is 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, which can excite optical signals of 2N+2 wavelengths in total. Since different resonant cavities correspond to different input and output port combinations of the wavelength division multiplexer 2, and these 2N+2 wavelengths correspond to the minimum loss wavelengths between the input and output ports of the wavelength division multiplexer 2, the multi-wavelength semiconductor laser can output up to 2N+2 different wavelengths of light, where each output semiconductor optical amplifier has N+1 wavelengths of laser output.

[0073] In general application scenarios, the output wavelengths of the multi-wavelength semiconductor laser are required to be continuous and have equal wavelength intervals. In order to meet this requirement, the corresponding minimum loss wavelength λ between each output port of the wavelength division multiplexer 2 should be optimized accordingly.

[0074] Define the minimum loss wavelength 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, j=1,2 represents the output port number. In order to satisfy the final output wavelength interval of Δλ, the input and output port positions are designed so that each wavelength satisfies: λ (i+1,j) - λ (i,j) =2Δλ λ (i,j+1) -λ (i,j) =3Δλ Thus, for the two output ports, the transmission spectrum superposition effect of different input channels is as follows: Figure 3 As shown, except λ 1,1 and λ N+1,2 Except for the two wavelengths, the intervals between the other 2N wavelengths are all Δλ. Therefore, the present invention can realize 2N continuous wavelength outputs, and the wavelength interval is Δλ.

[0075] In the above design, the output port wavelength interval 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 commonly used wavelength division multiplexers, such as arrayed waveguide gratings or etched diffraction gratings, the smaller the corresponding 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 splitting ability of 2Δλ wavelength interval light, and multi-wavelength laser output with a wavelength interval of Δλ can be realized, so the entire device has a smaller size, which is conducive to the realization of multi-wavelength semiconductor lasers with more output wavelengths.

[0076] In the present invention, a total of N+3 semiconductor optical amplifiers are used to achieve 2N consecutively spaced wavelength outputs. The dual-channel multiplexing design effectively reduces the number of required semiconductor optical amplifiers, and is also conducive to achieving a multi-wavelength semiconductor laser with more output wavelengths.

[0077] The two semiconductor optical amplifiers in the output semiconductor optical amplifier array each output an optical signal with N+1 wavelengths. In application, the two optical paths need to be combined into one output by the optical combiner 5. According to different implementations of the optical combiner, the present invention is divided into the following two embodiments. Embodiment 1:

[0078] In Embodiment 1 of the present invention, all parts of the semiconductor multi-wavelength semiconductor laser are integrated on the same chip. The partial reflector 4 is realized on the chip by deep etching grooves, and the beam combiner 5 is realized on the chip by means of a Y-branch beam combiner, a multi-mode interference coupler, etc.

[0079] Figure 4 The schematic diagram of the structure of the Y-branch combiner solution used for the combiner 5 is shown. The Y-branch combiner consists of an input waveguide 501, a coupling region 502, and an output waveguide 503, wherein the input waveguide 501 consists of two vertically symmetrical waveguides, and 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 merging the light from the two waveguides into one waveguide.

[0080] Figure 5 Schematic diagram of the composition structure of the multimode interference coupler solution for the combiner 5. The multimode interference coupler is composed of an input waveguide 501, a multimode interference region 504, and an output waveguide 503, wherein the input waveguide 501 is composed of two waveguides that are symmetrical up and down. After the light entering from one waveguide is imaged by interference in the multimode interference region, it is coupled into the output waveguide, and the function of light merging from two waveguides into one waveguide can also be realized. Preferably, in order to reduce the coupling loss, a tapered gradient waveguide 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.

[0081] The chip design scheme of Example 1 is as follows Figure 6 As shown. In the example, the wavelength division multiplexer 2 uses an etched diffraction grating, and the photosynthesizer 5 uses a Y-branch combiner. All parts of the semiconductor multi-wavelength semiconductor laser are integrated on the same chip. The input semiconductor optical amplifier array 1 and the output semiconductor optical amplifier array 3 are made on active semiconductor materials that can provide optical gain, the wavelength division multiplexer 2, the partial reflector 4 and the photosynthesizer 5 are made on passive semiconductor materials with lower optical loss, and the active materials and the passive materials can be integrated on the same substrate by monolithic integration or heterogeneous integration. This embodiment has the most compact structure and the smallest device size. Embodiment 2:

[0082] Since an on-chip optical combiner generally has a loss of 3 dB, in order to reduce the loss, the combiner 5 in Example 2 uses a fiber combiner.

[0083] 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 monolithic integration or heterogeneous integration. The partial reflector 4 is realized by etching the end face or cleaving the end face, and the combiner 5 is a fiber combiner. The design scheme of Embodiment 2 of the present invention is as follows Figure 7As 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. The use of an optical fiber combiner in Example 2 increases the complexity of the device, but the optical fiber combiner has lower loss and can achieve better laser output quality.

[0084] Comparative Example: In patent CN201310230999.4 and patent CN116683291A, wavelength selection is performed by making a grating in the active layer to achieve multi-wavelength output. Compared with the above comparative examples, the present invention uses a specially prepared multi-channel semiconductor optical amplifier array and a wavelength division multiplexer to achieve multi-wavelength output. The required manufacturing process is simple, only one etching process is required, and no high-precision grating manufacturing process is required (grating manufacturing needs to reach nm-level accuracy, and the manufacturing of each device in the present invention only requires μm-level accuracy), and no upper cladding layer needs to be grown again, so the requirements for manufacturing equipment are small and the manufacturing cost is low.

[0085] In patent CN201410613588, multi-wavelength output is achieved by integrating semiconductor optical amplifiers, phase modulators, arrayed waveguide gratings, etc. The semiconductor optical amplifier used is prepared by etching the ohmic contact layer. The present invention uses a specially prepared multi-channel semiconductor optical amplifier array. Each semiconductor optical amplifier is prepared by etching the upper cladding layer. 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 has only one output port. In order to achieve 2N output wavelengths, 2N semiconductor optical amplifiers are required. The present invention uses a wavelength division multiplexer with dual-channel multiplexed output, and only N+3 semiconductor optical amplifiers are needed to achieve 2N output wavelengths.

[0086] The above specific implementations are used to explain the present invention, rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention. The above description is only a preferred implementation of the present invention, so any equivalent changes or modifications made according to the structure, features and principles described in the scope of the patent application of the present invention are included in the scope of the patent application of the present invention.

Claims

1. A multi-wavelength semiconductor laser based on dual-channel multiplexing output, characterized in that: The laser light source part mainly 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.

2. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 1, characterized in that: The wavelength division multiplexer (2) has N+1 input ports, and two output ports are respectively connected to two 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 an operating wavelength of 3Δλ.

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), 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. 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.

4. A multi-wavelength semiconductor laser based on dual-channel multiplexing output according to any one of claims 1 to 3, 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.

5. 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.

6. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 5, 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.

7. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 5, 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.

8. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 7, 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 an optical signal.

9. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 7, 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.

10. 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.

11. The multi-wavelength semiconductor laser based on dual-channel multiplexing output according to claim 9, 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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