A tunable narrow-linewidth multi-wavelength laser

Abstract

The present invention relates to the technical field of semiconductor lasers and specifically provides a tunable narrow-linewidth multi-wavelength laser. The laser comprises: a laser, a microring, a 1×N-port optical splitter, a photoacoustic frequency shifter, an N×1-port coupler, and a semiconductor optical amplifier, all integrated on a waveguide layer of a chip. The laser and the microring form a stable injection-locked relationship, stabilizing the frequency of the laser output light near the resonant frequency of the microring. The optical signal is then split into multiple beams by the optical splitter, and each beam is frequency-modulated by the photoacoustic frequency shifter to achieve equally spaced multi-wavelength output. The beams are then combined by a coupler, and the optical signal is amplified by a semiconductor optical amplifier to achieve multi-wavelength output with narrow linewidth and adjustable wavelength intervals. Furthermore, the various components of the present invention are integrated on the same chip, avoiding the drawbacks of traditional solutions with multiple independent lasers, such as difficulty in controlling wavelength intervals and narrowing linewidths, as well as large system volume and complex structure.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor lasers, and in particular relates to a tunable narrow-linewidth multi-wavelength laser. Background Art

[0002] With the continuous development of optical communications, optical sensing, and other optical applications, the demand for multi-wavelength lasers is increasing. These lasers can simultaneously output laser signals at multiple wavelengths and are widely used in dense wavelength division multiplexing (DWDM) systems, spectral analysis, lidar, sensors, and optical communication systems. Traditional multi-wavelength light source systems often rely on arrays of multiple independent laser sources (such as DFB laser arrays). While these systems can provide multi-wavelength output, they suffer from several significant drawbacks in practical applications. First, the wavelength spacing is difficult to precisely control. Existing technologies often limit the tuning range and stability of wavelength spacing, especially in applications requiring high-precision wavelength selection. Second, these multi-wavelength lasers often require multiple independent light sources and complex optical components, resulting in a large, complex system, difficult assembly, and high cost. Furthermore, the coupling efficiency between the multiple laser sources is low, and the optical path losses are high, further impacting system performance and stability. Finally, multi-wavelength array light sources struggle to achieve a small linewidth, making them incapable of achieving more demanding and precise measurements. Summary of the Invention

[0003] In light of this, the present invention aims to provide a tunable narrow-linewidth multi-wavelength laser. This technology achieves beam linewidth compression through injection locking and frequency modulation of each split beam, achieving equally spaced multi-wavelength output. This addresses the problems of large linewidth and difficult-to-control wavelength spacing in conventional multi-wavelength lasers. Furthermore, the present invention integrates the light source, microring, coupler, photoacoustic frequency shifter, and amplifier into the waveguide layer of a single chip, effectively reducing the overall size and avoiding the drawbacks of conventional systems requiring multiple independent lasers.

[0004] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0005] The present invention provides a tunable narrow-linewidth multi-wavelength laser, comprising:

[0006] a light source for providing an optical signal;

[0007] A microring is connected to the rear optical path of the light source. The light source and the microring form an injection-locked relationship to limit the linewidth of the optical signal.

[0008] A 1×N-port optical splitter, whose input port is connected to the micro-ring, is used to split the optical signal output by the micro-ring into N beams of light;

[0009] A photoacoustic frequency shifter is installed on the optical path behind each output port of the 1×N-port splitter. The frequency of each beam of light is adjusted by the photoacoustic frequency shifter to achieve equally spaced multi-wavelength output of N beams of light.

[0010] The N×1-port coupler has N input ports connected to the N output ports of the 1×N-port optical splitter, and is used to combine N beams of light modulated by the photoacoustic frequency shifter.

[0011] Preferably, the device includes integrated on the same chip waveguide layer: a semiconductor optical amplifier connected to the rear optical path of the output port of the coupler with N×1 ports.

[0012] Preferably, the light source is a single-mode laser.

[0013] Preferably, when the optical signal output by the light source is input into the microring, the optical signal satisfying the following relationship is emitted from the output port of the microring, and the remaining optical signal is reflected back to the light source by the microring:

[0014] ;

[0015] in, represents the output frequency of the light source, represents the resonant frequency of the microring cavity, Indicates the preset frequency deviation threshold.

[0016] Preferably, the preset frequency deviation threshold is changed by adjusting the quality factor of the microring, the line width of the light source, the injection power or the coupling coefficient between the microring and the light source. .

[0017] Preferably, the 1×N port optical splitter is a multimode interference optical splitter, an arrayed waveguide grating-based optical splitter, or a fiber grating-based optical splitter.

[0018] Preferably, the coupler of the N×1 ports is a multimode interference coupler, a coupler based on an arrayed waveguide grating, or a coupler based on a fiber grating.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0020] The present invention uses a laser as the main light source and a microring as the slave light source, and bonds and integrates the laser, microring, spectrometer, photoacoustic frequency shifter, coupler and semiconductor optical amplifier on the same chip, effectively improving the integration of multi-wavelength lasers and solving the problems of large system volume, complex structure and low integration in traditional design solutions with multiple independent lasers. In addition, existing multi-wavelength lasers cannot achieve laser linewidth compression, and the wavelength interval control of each laser source is difficult and the wavelength interval accuracy is low.

[0021] This invention uses injection locking between a DFB laser and a microring to narrow the laser's output linewidth, locking the output wavelength to a specific frequency. The output light is then split into separate beams, and the frequency of each beam is adjusted using a photoacoustic frequency shifter, achieving equally spaced multi-wavelength output. The design of the photoacoustic frequency shifter enables more precise wavelength control. The injection locking technique effectively reduces the laser's linewidth and improves the stability of the wavelength spacing, ensuring high precision and adjustability of the multi-wavelength output, meeting the needs of fields such as high-precision optical communications and spectral analysis.

[0022] Traditional multi-wavelength laser systems require external amplifiers to enhance optical signals, a process that introduces additional losses and reduces integration. However, the present invention integrates semiconductor laser amplifiers on-chip, avoiding the losses introduced by external amplifiers. While improving power amplification efficiency, it also ensures that the laser signal maintains good coherence and spectral characteristics during the amplification process, further enhancing the overall performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 2 is a schematic diagram of a waveguide layer structure of a tunable narrow-linewidth multi-wavelength laser provided in an embodiment of the present invention;

[0025] Figure 2 2 is a schematic structural diagram of a tunable narrow-linewidth multi-wavelength laser provided by an embodiment of the present invention, not showing an electrode layer;

[0026] Figure 3 is a schematic structural diagram of a tunable narrow-linewidth multi-wavelength laser showing an electrode layer according to an embodiment of the present invention;

[0027] Figure 4 2 is a diagram showing the main structure of a photoacoustic frequency shifter provided according to an embodiment of the present invention.

[0028] Reference numerals include:

[0029] Substrate 1, lower cladding 2, light source 31, microring 32, 1×N port spectrometer 33, photoacoustic frequency shifter 34, N×1 port coupler 35, semiconductor optical amplifier 36, upper cladding 4, electrode layer 5, piezoelectric material 341, and slotted electrode 342. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention. Similar elements in different embodiments use associated similar element numbers. In the following embodiments, many detailed descriptions are intended to enable the present invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present invention are not shown or described in the specification. This is to avoid the core part of the present invention being overwhelmed by too much description. For those skilled in the art, it is not necessary to describe these related operations in detail. They can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0031] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various orders in the description and the drawings are only for the purpose of clearly describing a certain embodiment and are not intended to be a required order, unless otherwise specified that a certain order must be followed.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0033] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0034] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0035] See also Figure 1 、 Figure 2 and Figure 3 In one embodiment of the present invention, a tunable narrow-linewidth multi-wavelength laser is provided. By integrating a light source 31, a microring 32, a 1×N-port optical splitter 33, a photoacoustic frequency shifter 34, an N×1-port coupler 35, and a semiconductor optical amplifier 36 on the same chip platform, this overcomes the drawbacks of traditional multi-wavelength lasers, such as large size and low integration. Injection locking technology effectively narrows the laser bandwidth, and photoacoustic frequency shifting is used to achieve precise control of equally spaced multi-wavelengths. Specifically, from a layered fabrication perspective, the laser comprises, from bottom to top, a substrate 1, a lower cladding 2, a waveguide layer, an upper cladding 4, and an electrode layer 5. The substrate 1 is a silicon-based material that provides mechanical support. During the fabrication process, a layer of silicon dioxide is deposited on the upper surface of the substrate 1 by deposition, serving as the lower cladding 2 of the waveguide layer. The silicon dioxide material can form a refractive index difference with the high-refractive-index waveguide layer material, confining the light field within the waveguide layer and preventing light field leakage. A layer of waveguide material is deposited on the upper surface of the lower cladding layer 2. Optional waveguide materials include but are not limited to silicon (Si), silicon nitride (SiNx), lithium niobate (LiNbO3), etc. After the waveguide material is deposited, the light source 31, microring 32, 1×N port spectrometer 33, photoacoustic frequency shifter 34, N×1 port coupler 35, and semiconductor optical amplifier 36 are integrated in the waveguide layer using photolithography and etching processes. After the functional devices of the waveguide layer are prepared, the upper cladding layer 4 and the electrode layer 5 are bonded and prepared. The function of the upper cladding layer 4 is similar to that of the lower cladding layer 2. Both of them confine the light field within the waveguide layer to avoid light field leakage. The electrode layer 5 is mainly provided with a power supply electrode for the light source 31, a voltage regulation electrode for the microring 32, and a power supply electrode for the photoacoustic frequency shifter 34 (i.e. Figure 4 The power supply interface of the interdigitated electrode 342 is shown), and the power supply electrode of the semiconductor optical amplifier 36.

[0036] A light source 31 is provided in the chip waveguide layer. In this embodiment of the present invention, a DFB laser is used to provide an optical signal. The gain medium of the DFB laser is a III-V material. The III-V material can be integrated with the passive waveguide material through bonding, secondary epitaxy, or micro-transfer printing. Alternatively, a DBR laser or other single-mode laser can be used. A microring 32 is provided in the optical path behind the light source 31. Specifically, the microring 32 is fabricated on the subsequent waveguide of the light source 31. The microring 32 interacts with the light source 31 through a coupling structure, forming a stable injection-locked relationship. After the optical signal output by the light source 31 is input into the microring 32, the interaction between the DFB laser and the microring 32, based on the principle of injection locking, can effectively adjust the output frequency of the DFB laser and lock the output frequency near the resonant frequency of the resonant cavity of the microring 32. Specifically, after the optical signal is injected into the microring 32, the optical signal whose frequency matches the resonant frequency of the resonant cavity of the microring 32 can be emitted through the output end of the microring 32 and continue to be transmitted to the rear-end optical waveguide, while the remaining frequency signal light is fed back to the light source 31. This part of the feedback light is injected into the light source 31 by the microring 32, affecting the output frequency of the light source 31. When the frequency of the feedback light is close to the resonant frequency of the microring 32 and meets certain phase and amplitude conditions, the output frequency of the light source 31 will be locked to the vicinity of the resonant frequency of the microring 32, achieving stable injection locking, compressing the bandwidth of the output laser, and solving the problem that the traditional multi-wavelength laser solution cannot obtain a smaller bandwidth. Among them, the signal light that can be emitted from the output port of the microring 32 to match the resonant frequency must meet the following conditions:

[0037] ;

[0038] in, represents the output frequency of the light source 31, represents the resonant frequency of the resonant cavity of the microring 32, represents the preset frequency deviation threshold, which represents the maximum frequency difference between the output frequency of the light source 31 and the resonant frequency of the micro-ring 32. It mainly depends on the quality factor of the micro-ring 32, the line width of the light source 31, the injection power and the coupling coefficient between the micro-ring 32 and the light source 31. Therefore, in practical applications, the preset frequency deviation threshold can be changed by adjusting the quality factor of the micro-ring 32, the line width of the light source 31, the injection power or the coupling coefficient between the micro-ring 32 and the light source 31 according to the line width requirements of the multi-wavelength laser output. , thereby changing the line width of the output laser of the multi-wavelength laser.

[0039] After achieving stable injection locking, the optical signal is emitted from the output port of microring 32. A 1×N-port optical splitter 33 is connected to the optical path behind the output port of microring 32, where "1" represents the number of input ports and "N" represents the number of output ports. After the optical signal enters 1×N-port optical splitter 33 from microring 32, it is split into N beams, each output from one of the N output ports. Each output port of 1×N-port optical splitter 33 is connected to one of the N input ports of an N×1-port coupler 35 in the optical path behind the microring. To achieve evenly spaced multi-wavelength output, these N beams must be frequency modulated. A photoacoustic frequency shifter 34 is installed in the optical waveguide path of each beam. Specifically, a photoacoustic frequency shifter 34 is installed in the optical path between the output port of 1×N-port optical splitter 33 and the input port of N×1-port coupler 35. N photoacoustic frequency shifters 34 correspond to each of the N beams. The frequencies of the corresponding light beams are adjusted by N photoacoustic frequency shifters 34, so that there is a fixed wavelength interval between the N beams of light. The frequency interval can be 10 MHz to hundreds of GHz, and the specific frequency interval can be adjusted according to actual needs. Among them, the 1×N port splitter 33 can choose to use a multimode interference splitter, an arrayed waveguide grating (AWG)-based splitter, or a fiber Bragg grating-based splitter to achieve splitting. The N×1 port coupler 35 can choose to use a multimode interference coupler (MIMI), an arrayed waveguide grating (AWG)-based coupler, or a fiber Bragg grating-based coupler to combine N beams of light with equally spaced wavelengths.

[0040] like Figure 4 As shown, the photoacoustic frequency shifter 34 mainly realizes the frequency regulation of the optical signal through the acousto-optic effect. Its structure includes a piezoelectric material 341 and a tooth electrode 342 connected to the piezoelectric material 341. By applying an alternating voltage to the piezoelectric material 341, the piezoelectric material 341 generates mechanical vibrations, namely ultrasonic waves. Ultrasonic vibrations are used to generate periodic changes in the refractive index in the optical waveguide, forming the medium required for the acousto-optic interaction. By changing the frequency of the voltage applied to the tooth electrode 342, the frequency of the ultrasonic wave generated on the piezoelectric material 341 can be controlled, thereby changing the frequency of the optical signal to achieve equally spaced multi-wavelength output. Among them, the special shape design of the tooth electrode 342 can ensure that the electric field is evenly distributed in the piezoelectric material 341, thereby generating uniform ultrasonic vibrations. Among them, the preparation material of the piezoelectric material 341 can be selected from lithium niobate (LiNbO3), lead zirconate titanate (PZT), polymer material (PVDF), zinc oxide (ZnO), etc.; the preparation material of the tooth electrode 342 can be selected from gold (Au), aluminum (Al), copper (Cu), titanium (Ti), silver (Ag), etc.

[0041] N frequency-adjusted light beams are injected along the optical waveguides from the N input ports of the N×1 coupler 35, combining the N beams of equally spaced wavelengths. The combined light beams are output from the output port of the N×1 coupler 35 and injected into a semiconductor optical amplifier 36 connected to the optical path downstream of the output port of the N×1 coupler 35. The semiconductor optical amplifier 36 performs power amplification, minimizing the adverse effects of coupling loss and transmission loss between multiple optical paths during on-chip transmission of the optical signal. The amplification gain of the semiconductor optical amplifier 36 can be adjusted by adjusting the voltage applied to the power supply electrode of the semiconductor optical amplifier 36 on the electrode layer 5. Because the semiconductor optical amplifier 36 utilizes an on-chip integrated design, it avoids losses caused by external amplification, effectively improving laser amplification efficiency and ensuring that the laser signal maintains good coherence and spectral characteristics during the amplification process. In addition, the semiconductor optical amplifier 36 can be replaced by an erbium-doped fiber amplifier (EDFA) or a Raman amplifier. However, the erbium-doped fiber amplifier (EDFA) or the Raman amplifier is difficult to integrate on a chip, has certain losses, and reduces the integration of the entire device.

[0042] In short, the above description is only a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this specification shall be included in the scope of protection of this specification.

[0043] The systems, devices, modules, or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0044] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0045] The various embodiments in this specification are described in a progressive manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiments are generally similar to the method embodiments, so the description is relatively simple. For relevant parts, refer to the description of the method embodiments.

Claims

1. A tunable narrow-linewidth multi-wavelength laser, characterized in that: Includes integrated waveguide layers on the same chip: a light source for providing an optical signal; A microring connected to the rear optical path of the light source, wherein the light source and the microring form an injection-locked relationship to limit the linewidth of the optical signal; a 1×N-port optical splitter, whose input port is connected to the microring and is used to split the optical signal output by the microring into N beams of light; A photoacoustic frequency shifter is provided on the rear optical path of each output port of the 1×N-port optical splitter, and the frequency of each beam of light is adjusted by the photoacoustic frequency shifter to achieve equally spaced multi-wavelength output of N beams of light; The N×1-port coupler has N input ports that are respectively connected to the N output ports of the 1×N-port optical splitter, and is used to combine N beams of light that have been frequency-modulated by the photoacoustic frequency shifter.

2. The tunable narrow-linewidth multi-wavelength laser according to claim 1, characterized in that: The invention comprises a semiconductor optical amplifier integrated on the same chip waveguide layer, which is connected to the rear optical path of the output port of the N×1 port coupler.

3. The tunable narrow-linewidth multi-wavelength laser according to claim 1, characterized in that: The light source is a single-mode laser.

4. The tunable narrow-linewidth multi-wavelength laser according to claim 1, characterized in that: When the optical signal output by the light source is input into the micro-ring, the optical signal that satisfies the following relationship is emitted from the output port of the micro-ring, and the remaining optical signal is reflected by the micro-ring back to the light source: ； in, represents the output frequency of the light source, represents the resonant frequency of the microring cavity, Indicates the preset frequency deviation threshold.

5. The tunable narrow-linewidth multi-wavelength laser according to claim 4, characterized in that: The preset frequency deviation threshold is changed by adjusting the quality factor of the microring, the line width of the light source, the injection power or the coupling coefficient between the microring and the light source. .

6. The tunable narrow-linewidth multi-wavelength laser according to any one of claims 1 to 5, characterized in that: The 1×N port optical splitter is a multimode interference optical splitter, an arrayed waveguide grating-based optical splitter, or a fiber grating-based optical splitter.

7. The tunable narrow-linewidth multi-wavelength laser according to claim 6, characterized in that: The coupler of the N×1 ports is a multimode interference coupler, a coupler based on an arrayed waveguide grating, or a coupler based on a fiber grating.

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