Multi-wavelength laser based on rare earth doped integrated waveguide and chirped Moire waveguide grating

Abstract

The invention provides a multi-wavelength laser based on a rare earth doped integrated waveguide and a chirp Moire waveguide grating. Comprising a bidirectional pump laser unit, a wavelength division multiplexing coupler, a rare earth doped integrated waveguide with a chirp Moire waveguide grating, a broadband grating reflector and a rare earth doped waveguide power amplification unit. The broadband grating reflector, the rare earth doped integrated waveguide with the chirp Moire waveguide grating and the rare earth doped waveguide power amplification unit are connected in sequence, the chirp Moire waveguide grating on the rare earth doped waveguide is equivalent to a multipoint chirp phase shift grating subjected to cosine apodization, and the method is realized by adopting a forward design method or a reverse design method. The two-way pump laser adopts two-way pumping to input the rare earth doped integrated waveguide through the wavelength division multiplexing coupler, a laser resonant cavity is formed at each phase shift point of the chirp Moire waveguide grating, and single-frequency laser is generated. According to the invention, the stable equal-wavelength-interval multi-wavelength laser is realized by using the rare earth doped integrated waveguide with the chirp Moire waveguide grating.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-wavelength lasers, and in particular to a multi-wavelength laser based on a rare earth doped integrated waveguide and a chirped moiré waveguide grating. Background Art

[0002] Data center optical interconnects urgently require high-capacity, high-speed optical communications. Wavelength division multiplexing (WDM) technology can significantly increase data transmission capacity. Multi-wavelength laser sources can simultaneously provide multiple wavelengths of single-frequency laser light, serving as the carrier light source for each channel in the WDM system. Consequently, many researchers have initiated research on multi-wavelength lasers.

[0003] Outputting multi-wavelength laser sources from a single optical fiber / waveguide has attracted considerable attention due to its ability to be used in conjunction with cascaded microring modulators to efficiently implement compact wavelength division multiplexing systems. Multiple methods exist for generating multi-wavelength laser sources, including traditional III-V DFB (Distributed Feedback Laser) / DBR (Distributed Bragg Reflectors) / external cavity semiconductor laser arrays, serial connection of multiple single-frequency semiconductor / fiber lasers of different wavelengths, semiconductor mode-locked lasers / quantum dot mode-locked lasers, optical Kerr microcavity frequency combs, cascaded electro-optic modulators, and supercontinuum broadening. While the traditional III-V DFB / DBR / external cavity semiconductor laser arrays are mature, they require precise control of the injection current for each laser, resulting in high system complexity and energy consumption. Furthermore, wavelength division multiplexers / demultiplexers and couplers are required for wavelength demultiplexing and combining to achieve multi-wavelength laser output from a single waveguide. The laser linewidth of semiconductor mode-locked lasers / quantum dot mode-locked lasers is on the order of 1–20 MHz and needs to be further narrowed. Optical Kerr microcavity frequency combs require precise tuning of the pump laser wavelength and the microcavity resonant frequency, making long-term stable operation challenging. The frequency spacing of both mode-locked lasers and Kerr microcavity frequency combs is determined by the resonant cavity length. Optical frequency combs based on cascaded electro-optic modulators and supercontinuum broadening can achieve tunable laser frequency spacing (10 to 50 GHz), but the overall system size is relatively large.

[0004] Multi-point phase-shifted gratings (MPGs) and multi-point equivalent phase-shifted gratings (EGPs) combined with various gain medium platforms are effective methods for achieving multi-wavelength laser output from a single waveguide. A chirped moiré grating can be viewed as a chirped phase-shifted grating with multiple phase-shifted points after cosine apodization. Some researchers have proposed a multi-point phase-shifted, multi-wavelength fiber laser based on a distributed Fabry–Pérot cavity. By shifting the phase mask by a displacement D and using a double exposure method, chirped fiber gratings (similar to a chirped Moiré fiber grating) are superimposed and written into an erbium-ytterbium co-doped photosensitive fiber, forming a distributed fiber laser resonator. This achieves multi-wavelength laser output with 8 and 16 wavelengths at a frequency interval of 50 GHz. However, the low precision of the artificially shifted phase mask during writing the fiber gratings affects the frequency spacing of the multi-wavelength laser. In 2007, another approach was proposed to equivalently create a superstructured multi-point phase-shifted fiber grating (MPG) in an erbium-ytterbium co-doped photosensitive fiber using a single exposure method, achieving multi-wavelength laser output with a frequency interval of 16 wavelengths at a frequency interval of 50 GHz. However, due to the presence of a certain degree of birefringence in optical fibers, the cross-section is not strictly circularly symmetrical, which causes the two orthogonal degenerate polarization states (x polarization mode and y polarization mode) in the laser resonator to degenerate, resulting in the emergence of light sources with similar frequencies but different polarization directions (usually the frequency interval between the two polarization states' longitudinal modes is on the order of hundreds of MHz), and triggering mode competition. If an integrated optical waveguide platform is used, the serious polarization mode competition problem in the optical fiber platform can be solved.

[0005] Some scholars have proposed using two chirped gratings superimposed on a III-V quantum well semiconductor to realize a superstructure multi-point phase-shifted grating with a relative displacement D. By changing the relative drive current applied to each cavity electrode, the frequency interval and output power of each laser frequency are controlled. However, in the end, only 5-wavelength lasing was achieved, and the power flatness of the output laser of each wavelength was also poor. Some scholars have used the reconstruction equivalent chirp (REC) technology to achieve an equivalent multi-point phase-shifted grating of a distributed Fabry–Pérot cavity with a relative displacement D. In the end, only 4-wavelength laser output was achieved, but the coupling coefficient of the reconstructed equivalent grating was low.

[0006] Based on a III-V / silicon heterogeneous integrated laser platform, some researchers have achieved the equivalent of a four-wavelength DFB laser using a non-apodized chirped multi-point π phase-shifted grating by varying the width of the silicon waveguide while maintaining a uniform grating period. However, due to the short cavity length and large chirp of the III-V laser, the wavelength control accuracy is not accurate enough. Compared with the III-V semiconductor platform, the rare-earth-doped integrated waveguide platform can easily realize longer gain waveguides. In recent years, the rare-earth-doped waveguide platform technology has made great progress, achieving significant improvements in both waveguide loss and gain coefficient.

[0007] In summary, multi-wavelength lasers provide multi-wavelength carrier laser light sources for wavelength division multiplexing optical communication systems in data center optical interconnects. However, current research still faces many challenges, including the integration of multi-wavelength laser devices, output power flatness, the number of wavelengths, and tunability. Summary of the Invention

[0008] The embodiments of the present invention provide a multi-wavelength laser based on a rare earth doped integrated waveguide and a chirped moiré waveguide grating, so as to realize a high-performance, highly integrated single waveguide output multi-wavelength laser light source.

[0009] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions.

[0010] A multi-wavelength laser based on a rare earth doped integrated waveguide and a chirped moiré waveguide grating, characterized by comprising: a bidirectional pump laser unit, a wavelength division multiplexing coupler, a rare earth doped integrated waveguide with a chirped moiré waveguide grating, a broadband grating reflector, and a rare earth doped waveguide power amplifier unit;

[0011] The broadband grating reflector, the rare earth doped integrated waveguide with the chirped moiré waveguide grating, and the rare earth doped waveguide power amplifier unit are connected in sequence and are all implemented on a single rare earth doped integrated photonic chip;

[0012] The chirped Moiré waveguide grating on the rare-earth-doped waveguide is equivalent to a multi-point chirped phase-shifted grating with cosine apodization, which is realized by either forward design or reverse design. The bidirectional pump laser uses bidirectional pumping to input the rare-earth-doped integrated waveguide through a wavelength division multiplexing coupler to provide the gain required to generate multi-wavelength lasers. An optimized chirped Moiré waveguide grating with multiple phase shift points is prepared on the rare-earth-doped integrated waveguide. A laser resonant cavity is formed at each phase shift point of the chirped Moiré waveguide grating, and single-frequency lasers are generated, thereby realizing multi-wavelength laser output from a single waveguide.

[0013] A broadband grating reflector is fabricated on a rare-earth-doped integrated waveguide and introduced outside the chirped Moiré waveguide grating multi-point phase-shift laser resonator. This allows for re-injection locking of multi-wavelength lasers into the multi-point phase-shift laser resonator, thereby narrowing the laser linewidth. A rare-earth-doped waveguide power amplifier unit is used to boost the output power of the multi-wavelength laser.

[0014] Preferably, the substrate material for forming the rare earth doped integrated waveguide includes silicon nitride, lithium niobate, lithium tantalate, potassium oxide, aluminum oxide, yttrium oxide, silicon oxide, tantalum oxide, niobium oxide, tellurium oxide, gallium oxide, bismuth oxide, zinc oxide, phosphorus oxide, phosphate, silicate and tellurate; or a mixed material thereof; or a combination thereof and a low-loss waveguide material.

[0015] Preferably, the rare earth doped ions of the rare earth doped integrated waveguide include erbium, ytterbium, bismuth, praseodymium, neodymium, thulium and holmium ions, providing gains in different bands of 1.5 μm, 1 μm, 1.3 μm and 2 μm.

[0016] Preferably, the chirped moiré waveguide grating is realized by etching corrugated teeth or point / line distributed teeth on a rare earth doped integrated waveguide, or, the grating is realized by femtosecond laser direct writing, and the waveguide grating is realized by Euler bending or quasi-Euler bending in a spiral waveguide to realize S-bend, and the arc waveguide and the straight waveguide are connected.

[0017] Preferably, the chirped Moire waveguide grating adopts a forward design or a reverse design. The forward-designed chirped Moire waveguide grating regards the gratings on both sides of the waveguide as "sub-gratings", and designs the gratings on both sides as chirped gratings with a chirp amount C. The chirped Moire grating is formed by superimposing them through a relative offset displacement D. The following three implementation schemes are included:

[0018] (1) The gratings on both sides of the waveguide are designed to have a linear variation in grating period to achieve a linear chirped grating. The starting period of the gratings on both sides of the waveguide differs by ΔΛ G , the waveguide width remains constant;

[0019] (2) The waveguide width is designed to change linearly gradually, and the grating period remains unchanged to realize a linear chirped grating. The grating periods on both sides of the waveguide are different and remain constant, and the period difference between the gratings on both sides of the waveguide is ΔΛ G ;

[0020] (3) The waveguide width and the grating period on both sides of the waveguide are kept constant, the starting positions of the gratings on both sides are relatively offset by D, and the gratings on both sides are reconstructed by equivalent chirping to realize a chirped moiré grating with a relative displacement of D;

[0021] The complex coupling coefficient of the chirped Moiré waveguide grating obtained by forward design contains an amplitude spectrum and a phase spectrum. The amplitude spectrum of the complex coupling coefficient has multiple periods. There is a π phase offset at the minimum point of the amplitude spectrum of the complex coupling coefficient. The refractive index modulation depth function has an equivalent phase shift of π at the envelope minimum point. The chirped Moiré waveguide grating is equivalent to a multi-point chirped phase-shifted grating with cosine toeing. At multiple phase shift points at different positions along the grating, the number and wavelength spacing of the output laser can be changed by changing the chirp amount C and relative displacement D of the chirped grating. The number and wavelength spacing of the multi-wavelength laser can be changed by changing the reflectivity and bandwidth parameters of the chirped grating.

[0022] Preferably, a reverse design is performed based on the amplitude spectrum and phase spectrum of the complex coupling coefficient of the forward-designed chirped moiré waveguide grating to obtain a reverse-designed chirped moiré grating;

[0023] The inversely designed chirped moiré grating has multiple phase shift points along the entire grating length. The refractive index modulation depth function exhibits a periodic variation similar to the "amplitude spectrum of the complex coupling coefficient," with a very small near-zero refractive index modulation depth at the phase shift point. The grating period corresponds to an "effective grating" period mutation peak at the equivalent phase shift point. There are two ways to achieve this "effective grating" period mutation:

[0024] (1) The waveguide width at the phase shift point remains unchanged, the period of the grating is gradually increased and then decreased, a heating electrode is added at the phase shift point, and the period and phase shift of the refractive index modulated grating at the phase shift point where the phase shift is desired is changed by heating the electrode;

[0025] (2) The grating period at the phase shift point changes linearly, the waveguide width gradually increases and then gradually decreases, and a heating electrode is added at the phase shift point. By heating the electrode, the period and phase shift of the refractive index modulated grating at the phase shift point where the phase shift is expected to be achieved are changed.

[0026] Preferably, the chirped Moire waveguide grating obtained by inverse design has a periodically apodized grating refractive index modulation depth function distribution. Mapping the grating refractive index modulation depth function distribution onto the inversely designed chirped Moire waveguide grating structure includes four implementation methods:

[0027] (1) Apodization of the refractive index modulation by etching depth. The refractive index modulation depth of the chirped moiré grating is controlled by the relationship between the refractive index modulation depth and the grating etching depth to achieve apodization.

[0028] (2) Horizontal misalignment refractive index modulation apodization, which controls the refractive index modulation depth of the chirped moiré grating by introducing a horizontal misalignment between the two “sub-gratings” formed on both sides of the waveguide to achieve apodization;

[0029] (3) Duty cycle refractive index modulation apodization, which controls the refractive index modulation depth of the chirped moiré grating by adjusting the duty cycle of the grating etching within one grating period to achieve apodization;

[0030] (4) Periodic phase refractive index modulation apodization is achieved by establishing the relationship between the amplitude of the periodic phase modulation function and the refractive index modulation depth of the chirped moiré grating.

[0031] Preferably, both ends of the edge of the chirped Moire waveguide grating obtained by forward design or reverse design are toe-cut, and toe-cut is introduced at each equivalent phase shift point of the chirped Moire waveguide grating, and a broadband grating reflector is introduced outside the cavity of the multi-point phase-shift laser resonant cavity of the chirped Moire waveguide grating.

[0032] Preferably, the forward design and reverse design methods of the chirped moiré waveguide grating are used for a three-five quantum dot / quantum well material monolithic integration platform or a three-five silicon / silicon nitride / tantalum oxide / lithium niobate / lithium tantalate and other heterogeneous integration platforms.

[0033] As can be seen from the technical solutions provided by the aforementioned embodiments of the present invention, the multi-wavelength laser of the present invention features a simple structure, compact size, and precise control of output wavelength. It is a high-performance, highly integrated single-waveguide multi-wavelength laser light source. The single-waveguide multi-wavelength laser generation system of the present invention primarily produces multi-wavelength, single-frequency, narrow-linewidth lasers in the 1550nm band, which is beneficial for fields such as ultra-high-speed coherent optical communications and microwave photonics.

[0034] Additional aspects and advantages of the present invention will be set forth in part in the following description, will become apparent from the following description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 A schematic diagram of the system structure for generating multi-wavelength lasers based on rare-earth doped integrated waveguides and chirped moiré waveguide gratings provided in an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of a fully etched rare earth erbium-doped silicon nitride optical waveguide structure provided in an embodiment of the present invention;

[0038] Figure 3 A schematic diagram and a partial magnified view of a forward-designed spiral chirped moiré grating provided in an embodiment of the present invention;

[0039] Figure 4 The coupling coefficient amplitude spectrum and phase spectrum obtained by simulating a chirped moiré grating of a forward design (or reverse design) provided in an embodiment of the present invention;

[0040] Figure 5 A transmission spectrum obtained by simulating a chirped moiré grating of a forward design (or reverse design) provided in an embodiment of the present invention;

[0041] Figure 6 An embodiment of the present invention provides an inversely designed chirped moiré grating, which is obtained by varying the effective grating period with the waveguide length;

[0042] Figure 7A schematic diagram of a reverse-designed spiral chirped moiré grating and a partially enlarged schematic diagram of two different phase mutation methods provided in an embodiment of the present invention.

[0043] Figure 8 A schematic diagram of an embodiment of the present invention providing a method for controlling laser wavelength and power by using a heating electrode at each phase shift point of a chirped moiré grating (taking a linear waveguide as an example).

[0044] Figure 9 A schematic diagram of a complex coupling coefficient amplitude spectrum and the energy in the laser cavity at each phase shift point of a chirped moiré grating provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention.

[0046] It will be understood by those skilled in the art that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the description of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, "connected" or "coupled" as used herein may include wireless connections or couplings. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0047] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which the present invention pertains. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such herein, will not be interpreted in an idealized or overly formal sense.

[0048] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each embodiment does not constitute a limitation on the embodiments of the present invention.

[0049] The present invention utilizes rare-earth-doped integrated waveguides to achieve the higher gain required for laser generation by creating a longer waveguide length, resolving the issue of shorter gain-length waveguides in III-V semiconductor platforms. An optimized chirped Moiré waveguide grating is fabricated on the rare-earth-doped integrated waveguide to form a multi-point phase-shifted laser resonant cavity with a large number of phase shift points. A laser resonant cavity is formed at each phase shift point, enabling multi-wavelength laser output with a greater number of wavelengths. Furthermore, the integrated waveguide platform can address the issue of laser polarization mode competition in the fiber platform. Introducing apodization with a chirped Moiré waveguide grating effectively suppresses the spatial hole burning effect in the laser. Using a broadband grating feedback external cavity to re-inject multi-wavelength laser light into the multi-point phase-shifted laser resonant cavity can narrow the laser linewidth. Based on a rare-earth-doped integrated waveguide with a chirped Moiré waveguide grating and in a spiral form, a single waveguide can be used to output multi-wavelength lasers in a compact on-chip layout.

[0050] The embodiment of the present invention provides a structural diagram of a multi-wavelength laser based on rare earth doped integrated waveguide and chirped moiré waveguide grating. Figure 1 As shown, it includes a bidirectional pump laser unit, a wavelength division multiplexing coupler, a rare earth doped integrated waveguide with a chirped moiré waveguide grating, a broadband grating reflector and a rare earth doped waveguide power amplifier unit.

[0051] A broadband grating reflector, a rare-earth-doped integrated waveguide with a chirped Moiré waveguide grating, and a rare-earth-doped waveguide power amplifier unit are sequentially connected and implemented on a single rare-earth-doped integrated photonic chip. The chirped Moiré waveguide grating on the rare-earth-doped waveguide can be equivalent to a multi-point chirped phase-shifted grating with cosine apodization. It is a key component for achieving multi-wavelength lasing and can be implemented using either forward or reverse design methods. A bidirectionally pumped laser uses bidirectional pumping, which is input into the rare-earth-doped integrated waveguide via a wavelength division multiplexing coupler to provide the gain required for multi-wavelength laser generation. An optimized chirped Moiré waveguide grating with multiple phase-shift points is fabricated on the rare-earth-doped integrated waveguide. A laser resonant cavity is formed at each phase-shift point of the chirped Moiré waveguide grating, generating single-frequency laser light. This enables multi-wavelength laser output from a single waveguide. A broadband grating reflector is fabricated on a rare-earth-doped integrated waveguide and introduced outside the chirped Moiré waveguide grating multi-point phase-shift laser resonator. This allows for re-injection locking of multi-wavelength lasers into the multi-point phase-shift laser resonator, thereby narrowing the laser linewidth. A rare-earth-doped waveguide power amplifier unit is used to boost the output power of the multi-wavelength laser.

[0052] Furthermore, the substrate material of the rare earth-doped integrated waveguide includes materials that are easy to implement rare earth ion doping, such as silicon nitride, lithium niobate, lithium tantalate, potassium oxide, aluminum oxide, yttrium oxide, silicon oxide, tantalum oxide, niobium oxide, tellurium oxide, gallium oxide, bismuth oxide, zinc oxide, phosphorus oxide, phosphate, silicate and tellurate, or their mixed materials. The waveguide can also be formed by combining with low-loss waveguide materials such as aluminum nitride, sulfide, silicon nitride, tantalum oxide, etc.

[0053] Furthermore, the rare-earth-doped integrated waveguides (IRWs) contain rare-earth dopants such as erbium, ytterbium, bismuth, praseodymium, neodymium, thulium, and holmium, providing gain in various wavelength bands, including 1.5μm, 1μm, 1.3μm, and 2μm. Compared to optical fiber, the use of IRWs can effectively reduce the size and footprint of multi-wavelength lasers, address polarization mode competition in fiber lasers, and improve the stability of multi-wavelength, single-frequency, single-polarization lasers.

[0054] Furthermore, the chirped moiré waveguide grating on the rare-earth-doped integrated waveguide can be achieved by etching rectangular, sinusoidal, triangular, or dot / line patterns onto the rare-earth-doped integrated waveguide, or by femtosecond laser direct writing. The waveguide grating has a length of 5-20 cm (and can be longer), and has a compact spiral shape, which helps conserve optical chip area. Euler bending / quasi-Euler bending is used to create S-bends in the spiral waveguide, connecting the circular waveguide to the straight waveguide, exciting only the fundamental mode and suppressing higher-order modes. The chirped moiré waveguide grating can be achieved using either forward or reverse design methods.

[0055] Furthermore, the chirped Moire waveguide grating is forward-designed by treating the gratings on both sides of the waveguide as "sub-gratings" and designing the gratings on both sides as chirped gratings with a chirp amount C. The chirped Moire waveguide grating is formed by superimposing them through a relative offset displacement D. There are three main implementation schemes:

[0056] (1) The gratings on both sides of the waveguide are designed to have a linear variation in grating period to achieve a linear chirped grating, but the starting period of the gratings on both sides of the waveguide differs by ΔΛ G , the waveguide width remains constant.

[0057] (2) The waveguide width is designed to change linearly while the grating period remains unchanged to achieve a linear chirped grating. Although the grating periods on both sides of the waveguide are different, they remain constant. The period difference between the gratings on both sides of the waveguide is ΔΛ G .

[0058] (3) The waveguide width and the grating period on both sides of the waveguide are kept constant, but the starting positions of the gratings on both sides are relatively offset by D. The gratings on both sides use the reconstruction equivalent chirp (REC) technology to equivalently realize a chirped Moiré waveguide grating with a relative displacement of D.

[0059] The forward design thus obtained the amplitude spectrum and phase spectrum of the complex coupling coefficient of the chirped Moiré waveguide grating. The amplitude of the complex coupling coefficient of the chirped Moiré waveguide grating has multiple periods, and there is a significant π phase offset at the minimum point of the amplitude spectrum of the complex coupling coefficient, that is, the refractive index modulation depth function has an equivalent phase shift of π at the envelope minimum point. In other words, the chirped Moiré waveguide grating can be equivalent to a multi-point chirped phase-shifted grating after cosine toeing, forming a laser resonant cavity at each phase shift point. Multiple phase shift points at different positions along the grating are the key to achieving multi-wavelength lasing. The number of output laser wavelengths and the wavelength spacing can be flexibly designed according to actual needs by changing the chirp amount C and relative displacement D of the chirped grating. The design parameters of the chirped grating, such as reflectivity and bandwidth, are based on the principle of meeting the requirements of the number of wavelengths and wavelength spacing of the multi-wavelength laser.

[0060] Furthermore, based on the amplitude spectrum and phase spectrum of the complex coupling coefficient of the forward-designed chirped Moiré waveguide grating, a reverse-designed chirped Moiré waveguide grating can be obtained, and the refractive index modulation depth distribution function and the distribution of the "effective grating period" along the length of the waveguide grating can be obtained.

[0061] Among them, there are multiple phase shift points along the entire grating length. The refractive index modulation depth function shows a periodic change similar to the "amplitude spectrum of the complex coupling coefficient". At the phase shift point, there is an extremely small near-zero refractive index modulation depth (similar to toeing). The grating period basically shows a linear change. However, the grating period corresponds to an "effective grating" period mutation peak at the equivalent phase shift point. That is, the "effective grating" period is actually the π phase shift of the refractive index modulation function converted into a change in the grating period. There are two ways to achieve the "effective grating" period mutation:

[0062] (1) The waveguide width at the phase shift point remains unchanged, and the period of the grating is gradually increased and then decreased. A heating electrode is added at the phase shift point, and the period and phase shift of the refractive index modulated grating at the phase shift point where the phase shift is desired is changed by heating the electrode.

[0063] (2) The grating period at the phase shift point changes linearly, and the waveguide width gradually increases and then gradually decreases. A heating electrode is added at the phase shift point. By heating the electrode, the period and phase shift of the refractive index modulated grating at the phase shift point where the phase shift is desired is changed.

[0064] Through the above two methods, the multi-wavelength laser realized by the rare-earth-doped integrated waveguide based on the inverse design of chirped Moiré waveguide grating has programmable capabilities. The phase shift amount of each phase shift point can be controlled by heating the electrode, thereby controlling whether laser can be generated at each phase shift point and controlling and adjusting the laser wavelength and power at each phase shift point.

[0065] Furthermore, based on the amplitude and phase spectra of the complex coupling coefficient of the forward-designed chirped Moire waveguide grating, the refractive index modulation depth function distribution of the periodically apodized grating is inversely designed. This refractive index modulation depth function distribution of the grating is mapped onto the inverse-designed chirped Moire waveguide grating structure. There are four main implementation methods:

[0066] (1) Apodization of the refractive index modulation by etching depth. The refractive index modulation depth of the chirped moiré grating is controlled by the relationship between the refractive index modulation depth and the grating etching depth, thereby achieving apodization.

[0067] (2) Horizontal misalignment refractive index modulation apodization: A horizontal misalignment (i.e., phase delay) is introduced between the two “sub-gratings” formed on both sides of the waveguide to control the refractive index modulation depth of the chirped moiré grating and achieve apodization.

[0068] (3) Duty cycle refractive index modulation apodization: The refractive index modulation depth of the chirped moiré grating is controlled by the duty cycle of the grating etching within one grating period to achieve apodization.

[0069] (4) Phase refractive index modulation apodization: Apodization is achieved by establishing the relationship between the amplitude of the periodic phase modulation function and the refractive index modulation depth of the chirped moiré grating.

[0070] Furthermore, the chirped moiré waveguide grating obtained by forward design or reverse design is characterized in that toe-cutting is adopted at both ends of the edge of the waveguide grating, so that the waveguide grating can smoothly transition to connect to the straight waveguide, thereby suppressing the sidelobe effect and FP effect, and reducing the grating delay ripple and waveguide connection loss.

[0071] Furthermore, a multi-wavelength laser based on a rare-earth-doped integrated waveguide and a chirped Moiré waveguide grating effectively suppresses spatial hole burning and narrows the laser linewidth due to the introduction of apodization at each equivalent phase shift point of the chirped Moiré waveguide grating. Furthermore, a broadband grating reflector is introduced outside the chirped Moiré grating multi-point phase-shift laser resonator to achieve re-injection locking of the multi-wavelength laser into the multi-point phase-shift laser resonator, thereby narrowing the laser linewidth.

[0072] Furthermore, the forward and reverse design methods of the chirped Moiré waveguide grating can also be used in a three-five quantum dot / quantum well material monolithic integration platform or a three-five silicon / silicon nitride / tantalum oxide / lithium niobate / lithium tantalate heterogeneous integration platform to realize multi-wavelength semiconductor lasers based on chirped Moiré waveguide gratings.

[0073] The multi-wavelength laser based on a rare-earth-doped integrated waveguide and a chirped Moiré waveguide grating proposed in this invention has the following beneficial effects: A rare-earth-doped gain waveguide is used to achieve the higher gain required for laser generation by using a longer waveguide length, resolving the issue of short gain-length waveguides in III-V semiconductor platforms. An optimized chirped Moiré waveguide grating fabricated on the rare-earth-doped integrated waveguide forms a multi-point phase-shifted laser resonant cavity with a large number of phase shift points. This effectively controls the polarization state of the generated laser, resolving the problem of laser polarization mode competition in the fiber platform, increasing the number of wavelengths of the output multi-wavelength laser, and improving the stability of the multi-wavelength, single-frequency, single-polarization laser source. Introducing apodization through the chirped Moiré waveguide grating effectively suppresses spatial hole burning and narrows the laser linewidth. Introducing a broadband grating reflector outside the chirped Moiré grating multi-point phase-shifted laser resonant cavity allows for re-injection locking of the multi-wavelength laser into the multi-point phase-shifted laser resonant cavity, further narrowing the laser linewidth. The rare-earth-doped gain waveguide with a chirped moiré waveguide grating adopts a compact spiral shape, effectively reducing the chip area and size of the laser. Using a heated electrode, the phase shift at the π phase break point can be flexibly controlled, achieving controllable output laser wavelength and power. A single electronic control system is required to realize multi-wavelength lasers, reducing energy consumption and costs.

[0074] Example 1

[0075] The doping elements in the rare earth doped integrated waveguide use rare earth doping ions with gain effect, and the rare earth doping ions can be erbium Er 3+ The TE0 fundamental mode waveguide exhibits gain in the 1550nm band by co-doping ions with erbium, ytterbium, bismuth, praseodymium, neodymium, thulium, and holmium ions. The waveguide substrate is constructed from a low-loss rare-earth-doped material platform, such as silicon nitride. Based on the rare-earth-doped integrated waveguide platform, a long spiral waveguide grating was designed and fabricated. The upper and lower sides of the waveguide were considered "sub-gratings," and the grating structures on both sides were designed to form a chirped Moiré waveguide grating, creating a laser resonant cavity with multiple phase shift points. A 1480nm bidirectional pump laser was bidirectionally pumped into the rare-earth-doped integrated waveguide via a wavelength division multiplexing coupler to provide the gain required for multi-wavelength laser generation. A laser resonant cavity was formed at each phase shift point of the chirped Moiré waveguide grating, generating single-frequency laser light, thus achieving multi-wavelength laser output from a single waveguide. A broadband grating mirror is fabricated on a rare-earth-doped integrated waveguide and introduced outside the chirped Moiré waveguide grating multi-point phase-shifted laser resonator. This allows multi-wavelength laser light to be re-injected and locked into the multi-point phase-shifted laser resonator, narrowing the laser linewidth. A power amplifier unit is used to boost the output power of the multi-wavelength laser. The broadband grating mirror, the rare-earth-doped integrated waveguide with the chirped Moiré waveguide grating, and the power amplifier unit are sequentially connected and implemented on a rare-earth-doped integrated photonic chip.

[0076] The implementation methods of chirped Moiré waveguide grating are mainly divided into two schemes: forward design and reverse design.

[0077] The first approach is to use a forward-designed chirped moiré waveguide grating to realize a multi-wavelength laser. A forward-designed chirped moiré grating can treat both sides of the waveguide as chirped grating "sub-gratings" with a chirp amount C. These sub-gratings are then superimposed by a relative offset displacement D to form a chirped moiré grating. There are three main implementation options:

[0078] (1) The gratings on both sides of the waveguide are designed to have a linear variation in grating period to achieve a linear chirped grating, but the starting period of the gratings on both sides of the waveguide differs by ΔΛ G , the waveguide width remains constant.

[0079] (2) The waveguide width is designed to change linearly while the grating period remains unchanged to achieve a linear chirped grating. Although the grating periods on both sides of the waveguide are different, they remain constant. The period difference between the gratings on both sides of the waveguide is ΔΛ G .

[0080] (3) The waveguide width and the grating period on both sides of the waveguide are kept constant, but the starting positions of the gratings on both sides are relatively offset by D. The gratings on both sides use the reconstruction equivalent chirp (REC) technology to equivalently realize a chirped moiré grating with a relative displacement of D.

[0081] A moiré grating is formed by superimposing two gratings with slightly different periods. This results in a moiré pattern of intensity along the grating's length, creating a π phase shift at the intersection, which results in a resonance peak (transmission peak) at the Bragg wavelength. Furthermore, if the grating period increases linearly from the near end to the far end, forming a chirped grating, the operating frequency band can be broadened, resulting in multiple π phase shifts and achieving multiple resonance peaks (transmission peaks).

[0082] The sub-grating period on the upper and lower sides of the chirped moiré grating waveguide can be expressed as:

[0083]

[0084] Where Λ0 is the period corresponding to the central wavelength of the grating, C represents the chirp coefficient of the grating, D represents the relative offset length of the chirped grating waveguides on both sides, and L represents the length of the grating.

[0085] The distribution of the complex coupling coefficient of the chirped moiré grating along the waveguide length can be expressed as follows:

[0086]

[0087] Here, m=1 represents the sub-grating on the upper side of the waveguide, and m=2 represents the sub-grating on the lower side of the waveguide. φ mIndicates the initial phase. For the convenience of calculation, G(z) can be written as the product of the slowly changing envelope of the complex coupling coefficient and the average chirped grating, that is:

[0088]

[0089] in, Δφ=φ1-φ2 ​​and κ(z) represents the slowly varying envelope of the complex coupling coefficient of the chirped moiré grating.

[0090] Here |κ(z)| is the amplitude spectrum of the complex coupling coefficient envelope of the chirped moiré grating, according to The refractive index modulation amplitude at any position of the grating can be obtained.

[0091] The wavelength interval between adjacent transmission peaks of the chirped moiré grating can be expressed as:

[0092]

[0093] In this embodiment, a chirped moiré waveguide grating is fabricated on an erbium-doped silicon nitride waveguide to realize a multi-wavelength laser. Because laser light is generated at each phase shift point in a relatively short waveguide length, a high refractive index modulation depth is required. Taking into account gain and grating waveguide loss factors, the width and height of the erbium-doped silicon nitride waveguide are 2100nm and 700nm, respectively. A schematic diagram of the waveguide cross-section is shown in FIG. Figure 2 As shown. The waveguide length is 10cm, the chirp amount of the chirped grating is C = 0.41nm / cm, the grating corrugation etching depth is 100nm, the grating center wavelength is 1550nm, and the corresponding center period is Λ0 = 460nm. In order to save the area occupied by the integrated waveguide chip, the waveguide grating adopts a compact spiral shape with a spiral waveguide spacing of 5μm. The chirped moiré waveguide grating layout on the erbium-doped silicon nitride waveguide obtained by forward design is shown as follows Figure 3 shown.

[0094] The amplitude spectrum and phase spectrum of the complex coupling coefficient of the linear chirped Moiré grating can be obtained by simulating the forward-designed linear chirped Moiré grating, such as Figure 4 As shown. Figure 4 It can be seen that there is a significant phase shift at the minimum point of the grating's complex coupling coefficient intensity, that is, the refractive index modulation function has an equivalent phase shift of π at the envelope minimum point. This means that the chirped moiré grating can be equivalent to a multi-point chirped phase-shifted grating with cosine apodization, forming a laser resonant cavity at each phase-shifted point. Multiple phase-shifted points at different positions along the grating are the key to achieving multi-wavelength lasing.

[0095] Figure 5The transmission spectrum of a chirped moiré grating has a central wavelength of 1550 nm. The wavelength spacing between adjacent transmission peaks of the multi-point phase shift is approximately 0.8 nm, ultimately enabling lasing with at least 16 wavelengths. It should be noted that the number and spacing of the output laser wavelengths can be flexibly designed based on actual needs by varying the chirp value C and relative displacement D of the chirped grating. Design parameters such as the reflectivity and bandwidth of the chirped grating are designed to meet the requirements for the number and spacing of wavelengths in a multi-wavelength laser.

[0096] The second approach utilizes a reverse-engineered chirped moiré grating to achieve a multi-wavelength laser. Simulating the spectrum of the forward-engineered chirped moiré grating using the transfer matrix method yields parameters such as the coupling coefficient and effective grating period. This information allows for reverse engineering to determine the physical structure of the reverse-engineered chirped moiré grating, primarily including structural parameters such as the grating corrugation shape, corrugation depth, and grating period.

[0097] First, the grating corrugation shapes mainly include rectangular, sawtooth triangle, sine shape, and can also be dot / line distributed tooth shape. Different grating corrugation shapes have different modulation depths on the grating refractive index, thus affecting the coupling coefficient. When the corrugation is rectangular, the coupling coefficient is κ = 2Δn / λ B When the ripple is sinusoidal, the coupling coefficient is κ=πΔn / λ B Although the grating intensity of the sinusoidal shape is smaller than that of the rectangular shape under the same corrugation width, and the reflectivity of the grating is lower, the grating intensity dynamic range that can be controlled by the sinusoidal corrugation is wider. Secondly, the grating period is mainly related to the grating Bragg wavelength, that is, Λ=λ / 2n eff The actual period variation of the reverse-designed grating can be compared to the effective period of the forward-designed chirped moiré grating, and the two correspond to each other. Finally, the maximum corrugation depth of the grating is determined by the maximum grating intensity.

[0098] According to the coupling coefficient of the chirped moiré grating, its refractive index depth modulation function has multiple periods. Therefore, the grating needs to be subjected to multi-period refractive index modulation apodization. The main implementation methods include etching depth apodization, horizontal offset apodization, duty cycle apodization, and periodic phase apodization. Here, two apodization methods are used as examples: etching depth refractive index modulation apodization and horizontal offset refractive index modulation apodization.

[0099] For the inversely designed chirped moiré waveguide grating, the functions of the upper and lower edges of the waveguide grating can be expressed as

[0100]

[0101] Among them, s(z) determines the corrugation shape of the grating, s(z)=sgn(z) represents a rectangular corrugation shape, and s(z)=sin(z) represents a sinusoidal corrugation shape. The detailed definitions of grating etching depth modulation and horizontal offset modulation are as follows:

[0102] (1) Etching depth modulation. This method directly assumes that there is a linear relationship between the grating intensity and the etching depth. The upper and lower edge functions of the waveguide grating can be expressed as:

[0103]

[0104] f l (z)=-f u (z)(10)

[0105] Among them, κ n (z) is the normalized value of the grating intensity |κ(z)|.

[0106] (2) Horizontal offset modulation. The grating intensity is controlled by introducing a phase delay Δφ(z) between the sub-gratings on both sides of the waveguide. The upper and lower edge functions of the waveguide grating can be expressed as:

[0107]

[0108] Where, Δφ(z)=2cos -1 (κ n (z)).

[0109] The effective period of the grating is the key parameter for inverse design. The effective transmission constant β in the longitudinal direction of the grating can be obtained by the phase of the complex coupling coefficient. The effective grating period is calculated as follows:

[0110]

[0111] The calculated “grating effective period” of the inverse-designed chirped moiré grating is as follows: Figure 6 As shown in the figure, the inverse-designed chirped moiré grating has a total of 17 phase shift points. As can be seen from the figure, each equivalent phase shift point of the inverse-designed chirped moiré grating corresponds to an effective grating period mutation peak. That is, the "effective grating period" is actually the π phase shift of the refractive index modulation function converted into a change in the grating period. Therefore, two methods are used to implement the phase mutation:

[0112] (1) The waveguide width at the phase shift point remains unchanged, and the period of the grating is gradually increased and then decreased. A heating electrode is added at the phase shift point, and the period and phase shift of the refractive index modulated grating at the phase shift point where the phase shift is desired is changed by heating the electrode.

[0113] (2) The grating period at the phase shift point changes linearly, and the waveguide width gradually increases and then gradually decreases. A heating electrode is added at the phase shift point. By heating the electrode, the period and phase shift of the refractive index modulated grating at the phase shift point where the phase shift is desired is changed.

[0114] Draw the layout of the reverse-engineered chirped moiré grating according to the design parameters, such as Figure 7 As shown. In order to save floor space, the reverse-designed chirped moiré waveguide grating on the rare-earth-doped integrated waveguide adopts a compact spiral shape, the spacing between adjacent waveguides is 5μm, and the waveguide grating length is 10cm. Through the above two methods of phase mutation, the multi-wavelength laser based on the rare-earth-doped integrated waveguide with the reverse-designed chirped moiré grating has programmable capabilities. The phase shift amount of each phase shift point can be controlled by the heating electrode, thereby controlling whether the laser can be generated at each phase shift point and controlling the adjustment of the laser wavelength and power at each phase shift point. The schematic diagram of using the heating electrode at each phase shift point of the chirped moiré grating (taking a linear waveguide as an example) to control the laser wavelength and power is shown in the figure below. Figure 8 shown.

[0115] Figure 9 This figure shows the amplitude spectrum of the complex coupling coefficient and the energy within the laser cavity at each phase shift point of the chirped moiré grating. Based on a rare-earth-doped material platform and a chirped moiré waveguide grating, single-port multi-wavelength laser output can be achieved. Furthermore, the forward and reverse design methods of this chirped moiré waveguide grating can also be applied to a monolithic integrated platform of 35 quantum dots / quantum wells or heterogeneous integrated platforms such as 35 silicon / silicon nitride / tantalum oxide / lithium niobate / lithium tantalate, to realize multi-wavelength semiconductor lasers based on chirped moiré gratings.

[0116] In summary, the embodiments of the present invention utilize rare-earth-doped gain waveguides to achieve the higher gain required for laser generation using longer waveguide lengths, resolving the issue of shorter gain waveguide lengths in III-V semiconductor platforms. Furthermore, an optimized chirped Moiré waveguide grating fabricated on a rare-earth-doped integrated waveguide forms a multi-point phase-shifted laser resonator with a large number of phase shift points. This effectively controls the polarization state of the generated laser, resolving the polarization mode competition issue in optical fiber platforms, increasing the number of wavelengths of multi-wavelength laser output, and improving the stability of the multi-wavelength, single-frequency, single-polarization laser source. Introducing apodization into the chirped Moiré waveguide grating effectively suppresses spatial hole burning and narrows the laser linewidth. Introducing a broadband grating reflector outside the chirped Moiré grating multi-point phase-shifted laser resonator allows for re-injection locking of the multi-wavelength laser into the multi-point phase-shifted laser resonator, further narrowing the laser linewidth. The rare-earth-doped gain waveguide with the chirped Moiré waveguide grating adopts a compact spiral shape, effectively reducing the chip area and size occupied by the laser. The heating electrode allows for flexible control of the phase shift at the π phase mutation point, enabling controllable output of the laser wavelength and power. A single electronic control system is required to implement a multi-wavelength laser, reducing energy consumption and costs. The multi-wavelength laser of the present invention boasts a simple structure, compact size, and precise control of output wavelengths. It represents a high-performance, highly integrated, single-waveguide multi-wavelength laser light source.

[0117] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of an embodiment, and the modules or processes in the accompanying drawings are not necessarily required to implement the present invention.

[0118] From the above description of the embodiments, it can be seen that those skilled in the art can clearly understand that the present invention can be implemented by means of software plus the necessary general-purpose hardware platform. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium such as ROM / RAM, a magnetic disk, or an optical disk, and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in various embodiments of the present invention or certain parts of the embodiments.

[0119] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple. For the relevant parts, refer to the partial description of the method embodiments. The device and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. A person of ordinary skill in the art can understand and implement it without making any creative efforts.

[0120] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A multi-wavelength laser based on rare earth doped integrated waveguide and chirped moiré waveguide grating, characterized in that: include: bidirectional pump laser units, wavelength division multiplexing couplers, rare earth doped integrated waveguides with chirped moiré waveguide gratings, broadband grating mirrors, and rare earth doped waveguide power amplifier units; The broadband grating reflector, the rare earth doped integrated waveguide with the chirped moiré waveguide grating, and the rare earth doped waveguide power amplifier unit are connected in sequence and are all implemented on a single rare earth doped integrated photonic chip; The chirped Moiré waveguide grating on the rare-earth-doped waveguide is equivalent to a multi-point chirped phase-shifted grating with cosine apodization, which is realized by either forward design or reverse design. The bidirectional pump laser uses bidirectional pumping to input the rare-earth-doped integrated waveguide through a wavelength division multiplexing coupler to provide the gain required to generate multi-wavelength lasers. An optimized chirped Moiré waveguide grating with multiple phase shift points is prepared on the rare-earth-doped integrated waveguide. A laser resonant cavity is formed at each phase shift point of the chirped Moiré waveguide grating, and single-frequency lasers are generated, thereby realizing multi-wavelength laser output from a single waveguide. A broadband grating reflector is fabricated on a rare-earth-doped integrated waveguide and introduced outside the chirped Moiré waveguide grating multi-point phase-shift laser resonator. This allows for re-injection locking of multi-wavelength lasers into the multi-point phase-shift laser resonator, thereby narrowing the laser linewidth. A rare-earth-doped waveguide power amplifier unit is used to boost the output power of the multi-wavelength laser.

2. The multi-wavelength laser according to claim 1, wherein The substrate materials for forming rare earth doped integrated waveguides include silicon nitride, lithium niobate, lithium tantalate, potassium oxide, aluminum oxide, yttrium oxide, silicon oxide, tantalum oxide, niobium oxide, tellurium oxide, gallium oxide, bismuth oxide, zinc oxide, phosphorus oxide, phosphates, silicates and tellurates; or mixed materials thereof; or combinations thereof with low-loss waveguide materials.

3. The multi-wavelength laser according to claim 1, wherein The rare earth doped integrated waveguide includes rare earth doping ions of erbium, ytterbium, bismuth, praseodymium, neodymium, thulium and holmium ions, providing gains in different wavebands of 1.5 μm, 1 μm, 1.3 μm and 2 μm.

4. The multi-wavelength laser according to claim 1, wherein The chirped moiré waveguide grating is realized by etching corrugated teeth or point / line distributed teeth on a rare earth doped integrated waveguide, or by using femtosecond laser direct writing to realize the grating. The waveguide grating uses Euler bending or quasi-Euler bending to realize S-bend in a spiral waveguide, and the arc waveguide is connected to the straight waveguide.

5. The multi-wavelength laser according to claim 4, characterized in that The chirped Moire waveguide grating adopts forward design or reverse design. The forward chirped Moire waveguide grating regards the gratings on both sides of the waveguide as "sub-gratings" and designs the gratings on both sides as chirped gratings with a chirp amount C. The chirped Moire grating is formed by superimposing them through relative offset displacement D. The chirped Moire grating includes the following three implementation schemes: (1) The gratings on both sides of the waveguide are designed to have a linear variation in grating period to achieve a linear chirped grating. The starting period of the gratings on both sides of the waveguide differs by ΔΛ G , the waveguide width remains constant; (2) The waveguide width is designed to change linearly gradually, and the grating period remains unchanged to realize a linear chirped grating. The grating periods on both sides of the waveguide are different and remain constant, and the period difference between the gratings on both sides of the waveguide is ΔΛ G ; (3) The waveguide width and the grating period on both sides of the waveguide are kept constant, the starting positions of the gratings on both sides are relatively offset by D, and the gratings on both sides are reconstructed by equivalent chirping to realize a chirped moiré grating with a relative displacement of D; The complex coupling coefficient of the chirped Moiré waveguide grating obtained by forward design contains an amplitude spectrum and a phase spectrum. The amplitude spectrum of the complex coupling coefficient has multiple periods. There is a π phase offset at the minimum point of the amplitude spectrum of the complex coupling coefficient. The refractive index modulation depth function has an equivalent phase shift of π at the envelope minimum point. The chirped Moiré waveguide grating is equivalent to a multi-point chirped phase-shifted grating with cosine toeing. At multiple phase shift points at different positions along the grating, the number and wavelength spacing of the output laser can be changed by changing the chirp amount C and relative displacement D of the chirped grating. The number and wavelength spacing of the multi-wavelength laser can be changed by changing the reflectivity and bandwidth parameters of the chirped grating.

6. The multi-wavelength laser according to claim 1, wherein According to the amplitude spectrum and phase spectrum of the complex coupling coefficient of the forward-designed chirped moiré waveguide grating, a reverse-designed chirped moiré grating is obtained by reverse-designing. The reverse-engineered chirped moiré grating has multiple phase-shift points along its entire length. The refractive index modulation depth function exhibits a periodic variation similar to the "amplitude spectrum of the complex coupling coefficient," with a minimal near-zero refractive index modulation depth at the phase-shift point. The grating period corresponds to a peak of "effective grating" period mutation at the equivalent phase-shift point. There are two ways to achieve this "effective grating" period mutation: (1) The waveguide width at the phase shift point remains unchanged, the period of the grating is gradually increased and then decreased, a heating electrode is added at the phase shift point, and the period and phase shift of the refractive index modulated grating at the phase shift point where the phase shift is desired is changed by heating the electrode; (2) The grating period at the phase shift point changes linearly, the waveguide width gradually increases and then gradually decreases, and a heating electrode is added at the phase shift point. By heating the electrode, the period and phase shift of the refractive index modulated grating at the phase shift point where the phase shift is expected to be achieved are changed.

7. The multi-wavelength laser according to claim 1, wherein: The chirped moiré waveguide grating obtained by inverse design has a periodically apodized grating refractive index modulation depth function distribution. There are four ways to map the grating refractive index modulation depth function distribution to the inversely designed chirped moiré waveguide grating structure: (1) Apodization of the refractive index modulation by etching depth. The refractive index modulation depth of the chirped moiré grating is controlled by the relationship between the refractive index modulation depth and the grating etching depth to achieve apodization. (2) Horizontal misalignment refractive index modulation apodization, which controls the refractive index modulation depth of the chirped moiré grating by introducing a horizontal misalignment between the two "sub-gratings" formed on both sides of the waveguide to achieve apodization; (3) Duty cycle refractive index modulation apodization, which controls the refractive index modulation depth of the chirped moiré grating by adjusting the duty cycle of the grating etching within one grating period to achieve apodization; (4) Periodic phase refractive index modulation apodization is achieved by establishing the relationship between the amplitude of the periodic phase modulation function and the refractive index modulation depth of the chirped moiré grating.

8. The multi-wavelength laser according to claim 1, wherein: Both ends of the chirped Moire waveguide grating obtained by forward design or reverse design are apodized, and apodization is introduced at each equivalent phase shift point of the chirped Moire waveguide grating. A broadband grating reflector is introduced outside the multi-point phase shift laser resonant cavity of the chirped Moire waveguide grating.

9. The chirped Moire waveguide grating according to claim 8, characterized in that: The forward design and reverse design methods of the chirped moiré waveguide grating are used for a three-five quantum dot / quantum well material monolithic integration platform or a three-five silicon / silicon nitride / tantalum oxide / lithium niobate / lithium tantalate and other heterogeneous integration platforms.

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