A tunable narrow-linewidth multi-wavelength laser based on injection locking

Abstract

The present invention relates to the field of semiconductor laser technology, specifically providing a tunable narrow-linewidth multi-wavelength laser based on injection locking. The laser comprises a light source, a beam splitter, a coupler, a photoacoustic frequency shifter, and a microring. The optical signal output by the light source is split into multiple sub-beams by the beam splitter. A photoacoustic frequency shifter and a microring are provided in the optical path of each sub-beam. The photoacoustic frequency shifter adjusts the frequency of the sub-beam, while the microring forms an injection-locked relationship with the light source, compressing the linewidth of the sub-beams. The sub-beams are then combined by a coupler, and finally a semiconductor optical amplifier is used for power amplification. By using the beam splitter, photoacoustic frequency shifter, and microring, the present invention enables a single light source system to output equally spaced multi-wavelength lasers, overcoming the drawbacks of traditional multi-light source designs.

Description

Technical Field

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

[0002] With the rapid development of optical communications and optical sensing technologies, the demand for multi-wavelength lasers is increasing in numerous fields, including dense wavelength division multiplexing systems, spectral analysis, lidar, and optical sensors. Traditional multi-wavelength light source systems primarily rely on arrays of multiple independent laser sources (such as DFB laser arrays) to achieve multi-wavelength output. However, these multi-light source systems face numerous challenges in practical applications. Firstly, traditional systems struggle to precisely control the spacing between different wavelength light sources. This is particularly true in applications requiring high-precision wavelength selection, where existing technologies exhibit significant limitations in tuning range and wavelength spacing stability. Secondly, the integration of multiple independent light sources and complex optical components results in a bulky and complex system, increasing assembly difficulty and cost. Furthermore, the coupling efficiency between the multiple light sources is low, resulting in significant optical path losses, which in turn impacts the overall system performance and stability. Furthermore, traditional multi-wavelength array light sources struggle to achieve a small linewidth, limiting their application in higher-precision measurement and precision detection. Summary of the Invention

[0003] In view of this, the present invention aims to provide a tunable narrow-linewidth multi-wavelength laser based on injection locking, which splits a single light source through a spectrometer, performs frequency modulation on each sub-optical path using a photoacoustic frequency shifter, and performs injection locking using a microring to narrow the linewidth of each sub-beam. The sub-beams are combined and adjusted by the photoacoustic frequency shifter and the microring, thereby realizing the output of multi-wavelength beams from a single light source and solving the problems of large linewidth and difficult-to-control wavelength intervals in traditional multi-wavelength 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 based on injection locking, comprising: a light source for providing an optical signal, a spectrometer, a coupler, a photoacoustic frequency shifter and a microring;

[0006] The optical signal output by the light source is divided into multiple sub-beams by a beam splitter. At least one photoacoustic frequency shifter and at least one microring are provided on the optical path of each sub-beam. The photoacoustic frequency shifter is used to adjust the frequency of the sub-beam. The microring forms an injection-locked relationship with the light source to reduce the linewidth of the sub-beam.

[0007] After micro-ring and micro-ring processing, multiple sub-beams are injected into the coupler, and the coupler combines all the sub-beams.

[0008] Preferably, the light source, the optical splitter, the coupler, the photoacoustic frequency shifter and the microring are all integrated on the same semiconductor chip, and light transmission is performed through the waveguide layer of the semiconductor chip.

[0009] Preferably, a semiconductor optical amplifier is also integrated on the semiconductor chip, and the combined light beams after being combined by the coupler are incident on the semiconductor optical amplifier for power amplification.

[0010] Preferably, the light source is a DFB single-mode laser.

[0011] Preferably, the circumferences of the micro-rings on the optical paths of different sub-beams are different.

[0012] Preferably, the waveguide layer of the semiconductor chip is made of lithium niobate material, and each photoacoustic frequency shifter and each microring is provided with an electrode.

[0013] Preferably, the frequency of the sub-beam is changed by adjusting the voltage applied to the corresponding electrode of the photoacoustic frequency shifter.

[0014] Preferably, by adjusting the voltage applied to the electrode corresponding to the microring, the lithium niobate waveguide section corresponding to the microring generates an electro-optical effect, thereby changing the refractive index of the microring and adjusting the resonant frequency of the microring.

[0015] Preferably, the resonant frequency of each microring is monitored. When the resonant frequency of any microring deviates from its preset value, the voltage applied to the corresponding microring electrode is controlled through closed-loop feedback to make the microring resonant frequency track the preset value and maintain the injection-locked state.

[0016] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0017] The present invention splits a single light source and uses a photoacoustic frequency shifter and a microring to process sub-beams. The injection locking technology is used to effectively narrow the linewidth of the sub-beams, and the photoacoustic frequency shifter is used to adjust the frequency, thereby greatly improving the control accuracy of the corresponding wavelength of each sub-beam. In addition, the coordinated control of the photoacoustic frequency shifter and the microring can also keep the wavelength intervals of multiple sub-beams consistent, thus solving the problems of large linewidth of each wavelength and low wavelength interval control accuracy of traditional multi-wavelength lasers.

[0018] In addition, the present invention can integrate the light source, spectrometer, coupler, photoacoustic frequency shifter and microring on the same chip through photolithography, bonding, secondary epitaxy or micro-transfer printing technology, effectively improving the integration of multi-wavelength lasers and solving the problems of traditional multi-wavelength lasers requiring multiple laser light sources, resulting in large system size, complex structure and low integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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:

[0020] Figure 1 Schematic diagram of the waveguide layer structure of a tunable narrow-linewidth multi-wavelength laser based on injection locking provided according to an embodiment of the present invention.

[0021] Reference numerals include:

[0022] Light source 1, spectrometer 2, photoacoustic frequency shifter 3, microring 4, coupler 5, semiconductor optical amplifier 6. DETAILED DESCRIPTION

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0028] See also Figure 1 In one embodiment of the present invention, a tunable narrow-linewidth multi-wavelength laser based on injection locking is provided. The laser includes: a light source 1, a 1×N port optical splitter 2, N photoacoustic frequency shifters 3, N microrings 4, an N×1 port coupler 5, and a semiconductor optical amplifier 6. The above devices are all integrated into the waveguide layer of the same chip. The material of the waveguide layer can be silicon, silicon nitride, or lithium niobate. The specific integration process can adopt photolithography, bonding, secondary epitaxy, or micro-transfer printing technology.

[0029] Light source 1 uses a DFB single-mode laser, which emits an optical signal that is then transmitted along a waveguide layer. A beam splitter 2 is installed on the waveguide in the subsequent optical path of the optical signal. This beam splitter 2 splits the optical signal output by light source 1 into N sub-beams. Splitter 2 has one input port for receiving the optical signal from light source 1 and N output ports for outputting the split sub-beams. The N sub-beams are transmitted through N waveguide sub-paths. Each waveguide sub-path is equipped with a photoacoustic frequency shifter 3 and a microring 4. The order of the photoacoustic frequency shifters 3 and microring 4 can be interchanged. The N sub-beams correspond to a total of N photoacoustic frequency shifters 3. The photoacoustic frequency shifters 3 adjust the frequency of the sub-beams and ensure a fixed frequency spacing between them, ranging from 10 MHz to hundreds of GHz.

[0030] The photoacoustic frequency shifter 3 achieves frequency modulation of sub-beams through the acousto-optic effect. Its functional components primarily consist of piezoelectric materials and electrodes. By varying the alternating voltage applied to the electrodes of the photoacoustic frequency shifter 3, the piezoelectric material is prompted to generate ultrasonic waves. Ultrasonic vibrations produce periodic refractive index variations in the optical waveguide, forming the medium required for acousto-optic interaction. By varying the frequency of the voltage applied to the electrodes, the frequency of the ultrasonic waves generated in the piezoelectric material can be controlled, thereby changing the frequency of the optical signal to achieve frequency modulation of different sub-beams. By adjusting the alternating voltage applied to the electrodes of the photoacoustic frequency shifter 3 according to the preset wavelengths or frequencies of the different sub-beams, multiple sub-beams with equally spaced wavelengths can be output.

[0031] To further compress the linewidth of each sub-beam, a microring 4 is designed on the optical waveguide of each sub-beam. Each microring 4 forms a stable injection-locked relationship with the light source 1, further compressing the linewidth of the sub-beam. When a sub-beam enters the microring 4, based on the principle of injection locking, the light in the sub-beam whose frequency matches the resonant frequency of the microring 4's resonant cavity can be emitted through the output end of the microring 4 and continue to propagate toward the back-end optical waveguide, while the light in the remaining frequency bands is reflected. Therefore, the frequency of the sub-beam output by the microring 4 is locked to near the resonant frequency of the microring 4, effectively compressing the output laser bandwidth and resolving the problem of traditional multi-wavelength laser solutions being unable to achieve a small bandwidth. Here, locking the sub-beam frequency to near the resonant frequency of the microring 4 means that light within a range including the resonant frequency can be emitted through the microring 4. To ensure that the sub-beams output by different microrings 4 maintain equidistant wavelengths, different microrings 4 need to have different circumferences to mismatch the preset frequency or wavelength of the corresponding sub-beam. It is important to note that when the microring 4 is placed in the waveguide optical path ahead of the photoacoustic frequency shifter 3, that is, between the beam splitter 2 and the photoacoustic frequency shifter 3, each microring 4 directly forms an injection lock with the light source 1. However, when the microring 4 is placed in the waveguide optical path behind the photoacoustic frequency shifter 3, that is, between the beam splitter 2 and the microring 4, the light source 1 outputs an optical signal. After being split by the beam splitter 2, the resulting sub-beams first pass through the photoacoustic frequency shifter 3 to achieve frequency shifting before passing through the microring 4. Therefore, the photoacoustic frequency shifter 3 indirectly affects the injection locking in this process, but does not affect the ability of the microring 4 to stabilize the wavelength and frequency of the sub-beams at specific values ​​through the feedback mechanism.

[0032] After the photoacoustic frequency shifter 3 and microring 4 have been collaboratively processed, the sub-beams are output with equally spaced wavelengths and narrow linewidths. These sub-beams are then combined through an N×1-port coupler 5. Coupler 5 has N input ports and one output port, combining the N frequency-modulated sub-beams and outputting them through the output port. A semiconductor optical amplifier 6 is located on the waveguide path downstream of the coupler 5's output port, providing power amplification and minimizing the adverse effects of coupling loss and transmission loss between multiple optical paths during on-chip transmission of the optical signal.

[0033] As an optional embodiment, the chip's waveguide layer is made of lithium niobate. Because lithium niobate exhibits an electro-optical effect, electrodes can be placed above the waveguide layer of each microring 4. By varying the voltage applied to the electrodes in the microring 4, the refractive index of the lithium niobate material, and therefore the refractive index of the microring 4, can be altered based on the electro-optical effect of the lithium niobate waveguide. This change in the refractive index of the microring 4 also alters the optical cavity length of its resonant cavity, further changing the resonant frequency of the microring 4. This design allows the frequency and wavelength of the output sub-beams, after adjustment by the photoacoustic frequency shifter 3 and microring 4, to be varied without changing the circumference of the microring 4. This avoids the situation where the circumference of the microring 4 cannot be changed after etching, resulting in uncontrollable frequency and wavelength of the output sub-beams.

[0034] Furthermore, a frequency detector can be installed on each sub-optical path to detect the resonant frequency offset of the microring 4 on each sub-optical path. When the ambient temperature changes, or the temperature of the laser increases due to long-term operation, a photomechanical effect will directly disturb the resonant frequency of each microring 4, destroying the original locked state. Therefore, a closed-loop feedback control mechanism can be established through the frequency detector. The frequency detector sends the detection data to the control system. The control system adjusts the voltage applied to the electrodes of the microring 4 based on the resonant frequency offset data of the microring 4 detected by the frequency detector, actively compensating for the effects of the photomechanical effect and environmental drift, driving the actual resonant frequency of the microring 4 to track the originally set preset value, maintaining the injection-locked state, and improving the stability of the laser output of the multi-wavelength laser.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 based on injection locking, characterized in that: include: Used to provide optical signal light source, optical splitter, coupler, as well as photoacoustic frequency shifter and microring; The optical signal output by the light source is divided into a plurality of sub-beams by the optical splitter. At least one photoacoustic frequency shifter and at least one microring are provided on the optical path of each sub-beam. The photoacoustic frequency shifter is used to adjust the frequency of the sub-beam. The microring forms an injection-locked relationship with the light source to reduce the linewidth of the sub-beam. The plurality of sub-beams after passing through the micro-ring and the micro-ring processing are incident upon the coupler, and the coupler combines all the sub-beams; The light source, the optical splitter, the coupler, the photoacoustic frequency shifter and the microring are all integrated on the same semiconductor chip, and light transmission is performed through the waveguide layer of the semiconductor chip; The waveguide layer of the semiconductor chip is made of lithium niobate material, and each photoacoustic frequency shifter and each microring is provided with electrodes; The frequency of the sub-beam is changed by adjusting the voltage applied to the corresponding electrode of the photoacoustic frequency shifter.

2. The tunable narrow-linewidth multi-wavelength laser based on injection locking according to claim 1, characterized in that: A semiconductor optical amplifier is also integrated on the semiconductor chip, and the combined light beams after being combined by the coupler are injected into the semiconductor optical amplifier for power amplification.

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

4. The tunable narrow-linewidth multi-wavelength laser based on injection locking according to claim 1, characterized in that: The circumferences of the micro-rings on the optical paths of different sub-beams are different.

5. The tunable narrow-linewidth multi-wavelength laser based on injection locking according to claim 1, characterized in that: By adjusting the voltage applied to the electrode corresponding to the microring, the lithium niobate waveguide section corresponding to the microring generates an electro-optical effect, thereby changing the refractive index of the microring and adjusting the resonance frequency of the microring.

6. The tunable narrow-linewidth multi-wavelength laser based on injection locking according to claim 5, characterized in that: The resonant frequency of each microring is monitored. When the resonant frequency of any microring deviates from its preset value, the voltage applied to the corresponding microring electrode is controlled through closed-loop feedback to make the microring resonant frequency track the preset value and maintain the injection-locked state.

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