A broadband tunable laser based on heterogeneous integration

Abstract

The application belongs to the field of optoelectronic devices, and specifically discloses a broadband tunable laser based on heterogeneous integration, which comprises: a first resonant cavity and a first bus waveguide are coupled on one side surface, used for receiving optical signals coupled into from the first bus waveguide, and performing intracavity resonance on the light meeting the first resonant cavity resonance condition, and then coupling and reflecting; a second resonant cavity and a second bus waveguide are coupled on one side surface, used for receiving optical signals coupled into from the second bus waveguide, and performing intracavity resonance on the light meeting the second resonant cavity resonance condition, and then coupling and reflecting; a heterogeneous integration gain module is coupled on the other end of the first and second bus waveguides, used for receiving the optical signals reflected by the first resonant cavity and the second resonant cavity, and providing stimulated radiation gain, and then coupling back to the first and second bus waveguides. Through the application, large-range single-longitudinal-mode wavelength continuous tuning beyond the free spectral range limit of a single Fabry-Perot cavity is realized.

Description

Technical Field

[0001] This application belongs to the field of optoelectronic devices, particularly the field of optoelectronic device manufacturing, and more specifically, relates to a broadband tunable laser based on heterogeneous integration. Background Technology

[0002] Optoelectronic device manufacturing is a broad and cutting-edge field, encompassing the design, development, and fabrication of active and passive optoelectronic components such as semiconductor light-emitting diodes (LEDs), photodetectors, optical modulators, optical waveguides, fiber optic devices, and various lasers. Among these, lasers, as core components of coherent light sources, possess irreplaceable application value in numerous fields including optical communication, intelligent sensing, healthcare, and precision detection. Narrow-linewidth tunable semiconductor lasers have important applications in coherent optical communication and frequency-modulated continuous wave (FMCW) lidar. In FMCW detection systems, addressing the frequency response nonlinearity and bandwidth limitations of traditional direct current modulation, the hybrid integration of semiconductor gain modules and low-loss photonic integrated chips has become a mainstream approach to improving light source performance. However, existing photonic integration platforms have inherent physical limitations in achieving high bandwidth and high linearity frequency sweeps: silicon or silicon nitride platforms that rely on thermo-optical effects have slow response and high power consumption, and thermal diffusion can easily lead to significant tuning nonlinearity; piezoelectrically tuned silicon nitride schemes are limited by mechanical hysteresis; and thin-film lithium niobate on insulator (LNOI) platforms are prone to significant DC drift under low-frequency sweeps or DC bias conditions, making it difficult to ensure the long-term operational stability of the light source.

[0003] In contrast, thin-film lithium tantalate on insulator (LTOI) offers an ideal material basis for developing high-speed, high-linearity electro-optic sweep lasers due to its high electro-optic coefficient, extremely low optical birefringence, significantly reduced DC drift effect, and mature wafer-level mass production capabilities. Furthermore, to overcome the bottlenecks of traditional end-coupled hybrid integration in terms of packaging tolerance, coupling loss, and mechanical stability, heterogeneous integration technology—integrating III-V group gain materials onto a thin-film lithium tantalate substrate and utilizing adiabatic mode conversion to achieve optical field coupling—is becoming a key evolutionary direction for realizing high-performance coherent light sources due to its high compactness, high reliability, and low-cost potential.

[0004] In existing hybrid integrated external cavity laser designs, single-mode lasing is typically achieved through wavelength-selective feedback structures on the external cavity chip. Common dual-micro-ring vernier structures offer a certain tuning range; however, their device size is relatively large, and due to the electro-optic anisotropy of crystals such as thin-film lithium tantalate, the modulation electrodes in the ring waveguide cannot be aligned with the electro-optic principal axis of the crystal around the entire circumference. This results in the modulation electric field acting only on a specific waveguide segment, leading to a physical upper limit on the overall electro-optic modulation efficiency. Furthermore, multi-ring systems are prone to mode competition. While a straight waveguide-based distributed Bragg reflector (DBR) structure perfectly accommodates electro-optic anisotropy, its ordinary structure has a fixed reflection wavelength. If a traditional sampled grating (SG-DBR) is used to generate a comb-shaped reflection spectrum in a straight waveguide configuration to achieve vernier tuning, a long cascaded grating structure is necessary to ensure reflectivity. This increases the physical size and insertion loss of the chip, and the phase matching between multiple gratings is complex, making it difficult for the device to simultaneously achieve a high edge mode rejection ratio and a compact on-chip area, affecting the wafer-level manufacturing yield and performance consistency.

[0005] In summary, the following technical needs exist in this field: There is an urgent need to propose a novel heterogeneous integrated thin-film external cavity laser architecture to fully leverage the high-efficiency electro-optic properties of thin-film lithium tantalate and the high-gain advantage of heterogeneous integration. This architecture must overcome the bottlenecks of existing filtering technologies and, while maintaining compatibility with thin-film electro-optic anisotropy, construct a novel lasing master cavity that combines wide-range vernier tuning capability, ultra-compact physical size, high side-mode suppression ratio, and a flexible on-chip optical signal extraction mechanism. This will comprehensively meet the stringent requirements of next-generation high-speed, high-precision detection and communication systems for high-performance on-chip light sources. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this application is to provide a broadband tunable laser based on heterogeneous integration, which aims to solve the problems of severe frequency sweep nonlinearity, complex packaging, and difficulty in achieving both compact size and wide-range continuous tuning in existing integrated frequency-modulated continuous wave lasers.

[0007] To achieve the above objectives, in a first aspect, this application provides a broadband tunable laser based on heterogeneous integration, comprising: a first bus waveguide, a second bus waveguide, a first resonant cavity, a second resonant cavity, and a heterogeneous integrated gain module; The first resonant cavity is coupled to the side of one end of the first bus waveguide to receive the optical signal coupled in from the first bus waveguide, and to resonate the light in the optical signal that meets the resonance condition of the first resonant cavity within the cavity, and then couple and reflect it to the first bus waveguide. The second resonant cavity is coupled to the side of one end of the second bus waveguide to receive the optical signal coupled in from the second bus waveguide, and to resonate the light in the optical signal that meets the resonance condition of the second resonant cavity within the cavity, and then couple and reflect it to the second bus waveguide. The two ends of the heterogeneous integrated gain module are coupled to the other ends of the first bus waveguide and the second bus waveguide, respectively, to receive the optical signals reflected by the first resonant cavity and the second resonant cavity, and to provide stimulated emission gain for the received optical signals, and then coupled back to the first bus waveguide and the second bus waveguide. One end face of the first or second bus waveguide is used to output the optical signal transmitted by the first or second resonant cavity as output light; wherein the first and second resonant cavities have different free spectral ranges, the first resonant cavity has a first reflection spectrum, and the second resonant cavity has a second reflection spectrum; the wavelength of the output light is determined by the main peak that coincides between the first and second reflection spectra.

[0008] In this process, the direction of optical signal coupling and reflection towards the first bus waveguide is opposite to the direction of optical signal coupling into the first resonant cavity; similarly, the direction of optical signal coupling and reflection towards the second bus waveguide is opposite to the direction of optical signal coupling into the second resonant cavity, so that the signal light is wavelength-selected and reflected through the first and second resonant cavities, forming a closed-loop feedback.

[0009] In one possible implementation, the first reflection spectrum and the second reflection spectrum have at least partial overlap in the wavelength domain. The heterogeneous integrated gain module is also used to generate spontaneous emission to provide an initial optical signal; the wavelength of the initial optical signal covers at least a portion of the overlapping bands.

[0010] In one possible implementation, the broadband tunable laser described above further includes: a first tuning electrode and / or a second tuning electrode; The first tuning electrode is used to perform translation tuning on the first reflection spectrum; The second tuning electrode is used to perform translation tuning on the second reflection spectrum; The first tuning electrode and / or the second tuning electrode are used to achieve vernier effect tuning of the output light.

[0011] In one possible implementation, the heterogeneous integrated gain module includes: an injection electrode and an active waveguide; The injection electrode is used to inject charge carriers into the active waveguide. The active waveguide has its two ends coupled to the other ends of the first bus waveguide and the second bus waveguide, respectively, and is used to provide stimulated emission gain for the optical signal under the action of charge carriers and optical signal.

[0012] In one possible implementation, the first or second resonant cavity includes: two Bragg gratings and a straight waveguide, which is coupled to the side of one end of a corresponding bus waveguide through the straight waveguide; The straight waveguide is used to connect two Bragg gratings; The first and second resonant cavities have different straight waveguide lengths; the parameters of the two Bragg gratings in each resonant cavity are the same.

[0013] In one possible implementation, the Bragg grating is a Gaussian apodized grating.

[0014] It should be noted that the Gaussian apodized grating provides a broadband, highly reflective stopband near the center wavelength, acting as a reflector and forming a resonant cavity structure between the two gratings. The bus waveguide and the resonant cavity are coupled, and only light of a specific wavelength that meets the resonant cavity resonance condition can resonate within the cavity and be reflected back to the bus waveguide, thus forming a series of comb-shaped reflection peaks with specific free spectral ranges in the frequency domain.

[0015] In one possible implementation, the broadband tunable laser described above further includes: a phase-tuning electrode; The phase-adjusting electrode is disposed above the first bus waveguide and / or the second bus waveguide, and is used to adjust the longitudinal mode phase of the total resonant cavity composed of the first resonant cavity, the first bus waveguide, the heterogeneous integrated gain module, the second bus waveguide, and the second resonant cavity, so that the longitudinal mode wavelength of the total resonant cavity is aligned with the main peak that coincides between the first reflection spectrum and the second reflection spectrum.

[0016] In one possible implementation, the other end of the first bus waveguide and the other end of the second bus waveguide are thermally coupled to the heterogeneous integrated gain module in the vertical direction.

[0017] In one possible implementation, the first bus waveguide, the second bus waveguide, the first resonant cavity, and the second resonant cavity are made of lithium tantalate or lithium niobate, and the heterogeneous integrated gain module is made of a III-V group semiconductor material.

[0018] Secondly, this application provides an application of a broadband tunable laser as described in the first aspect above in a broadband tunable light source, laser, and / or lidar emitting system.

[0019] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages: This application provides a broadband tunable laser based on heterogeneous integration. By directly bonding a III-V group gain medium to an electro-optic material thin-film chip using heterogeneous integration technology, a smooth transition of the optical field between the active layer and the passive waveguide layer is achieved using an adiabatic mode converter. This on-chip integration method avoids the complex spatial alignment and packaging process of traditional end-coupled external cavity lasers, significantly reducing coupling loss and solving the problems of small packaging tolerance and poor long-term mechanical stability. Simultaneously, the heterogeneous integration structure improves the device's compactness, facilitating low-cost, large-scale wafer-level manufacturing.

[0020] This application provides a broadband tunable laser based on heterogeneous integration, employing a cascaded Bragg grating Fabry-Perot resonator with a side-coupled straight waveguide structure as the wavelength-selective feedback element. The straight waveguide configuration allows the modulation electrode to achieve full physical coverage along the waveguide axis, ensuring constant alignment of the tuning electric field direction with the electro-optic principal axis of the electro-optic crystal. This design avoids the modulation efficiency degradation problem caused by the mismatch between the electric field and the crystal principal axis due to waveguide bending in micro-ring resonator structures, maximizing the utilization of the material's electro-optic tensor, reducing the driving voltage, and improving tuning efficiency.

[0021] This application provides a broadband tunable laser based on heterogeneous integration, which generates a vernier effect by cascading two short-cavity side-coupled Fabry-Perot resonators with different free spectral ranges. This mechanism allows the laser to achieve ultra-wide-range continuous tuning of a single longitudinal mode wavelength, exceeding the limitations of a single Fabry-Perot cavity's free spectral range, while maintaining an extremely short physical cavity length and reducing chip size. This structure has better tolerance to dimensional errors in processing, such as etching depth and linewidth fluctuations, significantly improving wafer yield and performance consistency under large-size wafer fabrication conditions. Attached Figure Description

[0022] Figure 1 A schematic diagram of the overall structure of a broadband tunable laser based on heterogeneous integration provided in an embodiment of this application; Figure 2 This is a schematic diagram of the resonant cavity structure provided in an embodiment of this application; Figure 3 A schematic diagram of the cross-sectional structure of a broadband tunable laser waveguide based on heterogeneous integration, provided for an embodiment of this application; Figure 4 A schematic diagram of the reflection spectrum of two resonant cavities provided in an embodiment of this application; Figure 5 This is a schematic diagram of the reflectivity product spectrum of two resonant cavities provided in an embodiment of this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0024] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0025] Furthermore, throughout this specification, references to "an embodiment"; "an embodiment," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. Therefore, the appearance of the phrase "in one embodiment;" throughout this specification, and similar language, may, but not necessarily, refer to the same embodiment.

[0026] First, the technical terms used in the embodiments of this application will be introduced.

[0027] (1) Free spectral range The free spectral range is an important concept in optics, referring to the frequency difference (i.e., the distance between two reflection peaks) between two adjacent resonant frequencies in an optical resonant cavity. In an optical resonant cavity, light reflects back and forth. When the wavelength of the light is equal to the length of the resonant cavity, the light is absorbed by the cavity, creating a resonance phenomenon. The free spectral range is a crucial parameter describing this resonance phenomenon.

[0028] (2) Vernier effect The vernier effect is a technique that utilizes two comb-shaped spectra with a small period difference to achieve high sensitivity and a wide range of wavelength selectivity or resonance modulation at the overlapping wavelength. It is widely used in tunable lasers, fiber optic sensors, and optical communication devices. Its principle is similar to that of vernier calipers: when the free spectral ranges of the two comb-shaped spectra differ slightly, they simultaneously satisfy the resonance condition only at a few wavelengths; a small change in refractive index causes one comb-shaped spectrum to shift, resulting in a shift in the overlapping peak, achieving sub-picometer precision or a wide range of tuning.

[0029] The embodiments of this application are described below with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic diagram of the overall structure of a broadband tunable laser based on heterogeneous integration, provided in an embodiment of this application; as shown. Figure 1As shown, it includes: a first bus waveguide 102, a second bus waveguide 104, a first resonant cavity 101, a second resonant cavity 105, and a heterogeneous integrated gain module 103; The first resonant cavity 101 is coupled to the side of one end of the first bus waveguide 102 to receive the optical signal coupled into the first bus waveguide 102, and to perform intracavity resonance on the light in the optical signal that meets the resonance condition of the first resonant cavity, and then couple and reflect it to the first bus waveguide 102. The second resonant cavity 105 is coupled to the side of one end of the second bus waveguide 104 to receive the optical signal coupled into the second bus waveguide 104, and to perform intracavity resonance on the light in the optical signal that meets the resonance condition of the second resonant cavity, and then couple and reflect it to the second bus waveguide 104. The two ends of the heterogeneous integrated gain module 103 are coupled to the other ends of the first bus waveguide 102 and the second bus waveguide 104, respectively, for receiving optical signals reflected by the first resonant cavity 101 and the second resonant cavity 105, and providing stimulated emission gain for the received optical signals, and then coupling back to the first bus waveguide 102 and the second bus waveguide 104. One end face of the first bus waveguide 102 or the second bus waveguide 104 is used to output the optical signal transmitted by the first resonant cavity 101 or the second resonant cavity 105 as output light; wherein the first resonant cavity 101 and the second resonant cavity 105 have different free spectral ranges, the first resonant cavity 101 has a first reflection spectrum, and the second resonant cavity 105 has a second reflection spectrum; the wavelength of the output light is determined by the main peak that coincides between the first reflection spectrum and the second reflection spectrum.

[0031] The direction of optical signal coupling and reflection towards the first bus waveguide 102 is opposite to the direction of optical signal coupling into the first resonant cavity 101; the direction of optical signal coupling and reflection towards the second bus waveguide 104 is opposite to the direction of optical signal coupling into the second resonant cavity 105. In some embodiments, the first reflection spectrum and the second reflection spectrum have at least partial overlap in the wavelength domain. The heterogeneous integrated gain module 103 is also used to generate spontaneous emission and provide an initial optical signal; the wavelength of the initial optical signal covers at least a portion of the overlapping bands.

[0032] In some embodiments, the broadband tunable laser described above further includes: a first tuning electrode 106 and / or a second tuning electrode 108. The first tuning electrodes 106 are disposed on both sides above the first resonant cavity 101 and are used to perform translation tuning on the first reflection spectrum. The second tuning electrode 108 is disposed on both sides above the second resonant cavity 105 and is used to perform translation tuning on the second reflection spectrum; The first tuning electrode 106 and / or the second tuning electrode 108 are used to achieve vernier effect tuning of the output light.

[0033] In some embodiments, the heterogeneous integrated gain module includes an active region waveguide 202 for providing optical gain; injection electrodes 201 and 203 distributed on both sides of the active region waveguide 202 for cooperating with the active region to provide the electric pump required for stimulated emission; injection electrodes for injecting carriers into the active region waveguide; and the active region waveguide having its two ends coupled to the other ends of the first bus waveguide and the second bus waveguide, respectively, for providing stimulated emission gain for the optical signal under the action of carriers and optical signal.

[0034] like Figure 2 As shown, the first resonant cavity 101 or the second resonant cavity 105 includes: two Bragg gratings 301 / 303 and a straight waveguide 302, which is coupled to the side of one end of the corresponding bus waveguide through the side of the straight waveguide 302. The straight waveguide 302 is used to connect two Bragg gratings; The straight waveguide 302 of the first resonant cavity and the second resonant cavity have different lengths; the parameters of the two Bragg gratings in each resonant cavity are the same.

[0035] In some embodiments, the Bragg grating is a Gaussian apodized grating. The transverse tooth depth perturbation of the grating satisfies a Gaussian envelope distribution along the waveguide propagation direction to suppress sidelobes of the reflection spectrum.

[0036] Figure 3 A schematic diagram of the cross-sectional structure of a broadband tunable laser waveguide based on heterogeneous integration provided in this application embodiment; as shown. Figure 3 As shown, the thin film layer 402 is made of lithium tantalate or lithium niobate. The thin film layer 402 is covered with an upper cladding layer 401 and a silicon dioxide buffer layer 403 is below it. The upper cladding layer 401 is air or silicon dioxide. An electrode 404 (such as a tuning electrode or a phase-tuning electrode) for tuning is disposed in the upper cladding layer 401.

[0037] In one specific embodiment, the thin film layer 402 is etched with a bottom bus waveguide that runs through the entire surface. The bottom bus waveguide includes a first bus waveguide 102 and a second bus waveguide 104 that are physically separated by the heterogeneous integrated gain module 103 and are optically connected, as well as a first resonant cavity 101 and a second resonant cavity 105 located on both sides of the bus waveguide.

[0038] The heterogeneous integrated gain module 103 is disposed between the first bus waveguide 102 and the second bus waveguide 104, and is used to provide stimulated emission amplification of optical signals.

[0039] The optical signal transmission path is as follows: the optical signal is bidirectionally transmitted and oscillates in the lasing main cavity composed of the first and second resonant cavities; in each oscillation cycle, the light from the first bus waveguide 102 or the second bus waveguide 104 is coupled into the active region waveguide 202, and after stimulated emission amplification, it is coupled back into the bottom bus waveguide; the optical signal is wavelength-selected and reflected via the first resonant cavity 101 and the second resonant cavity 105 to form a closed-loop feedback; in addition, part of the optical signal is transmitted through the second resonant cavity 105, continues to be transmitted along the second bus waveguide 104 and finally exits from its end face as the output of the laser.

[0040] It is understandable that the aforementioned reciprocating oscillation specifically includes: an optical field generated and amplified in the active waveguide, propagating to the left, and then thermally coupled downwards into the first bus waveguide via the thermal coupling structure at the left end. Additionally, an optical field generated and amplified in the active waveguide, propagating to the right, and then thermally coupled downwards into the second bus waveguide via the thermal coupling structure at the right end.

[0041] Similarly, the light reflected back by the first and second resonant cavities will also be vertically coupled upwards back to the top active region waveguide via the first and second bus waveguides, respectively, to complete closed-loop oscillation.

[0042] Furthermore, light that is not coupled into the second resonant cavity will be directly transmitted and output. That is, the second resonant cavity will not necessarily completely reflect the light; some light will be transmitted.

[0043] For example, the first bus waveguide 102 and the second bus waveguide 104 extend into the heterogeneous integrated gain module 103 at their ends in a conical structure to form an adiabatic coupling structure; the two ends of the active region waveguide 202 overlap vertically with the conical structures at the ends of the first bus waveguide 102 and the second bus waveguide 104, respectively; the bidirectional reciprocating optical field in the lasing main cavity achieves vertical adiabatic coupling between the bottom first bus waveguide 102 or the second bus waveguide 104 and the top active region waveguide 202 through the adiabatic coupling structure.

[0044] The first resonant cavity 101 and the second resonant cavity 105 are composed of two Bragg gratings 301 and 303, and a straight waveguide 302 connected between them, connected in series along the waveguide transmission axis; the first resonant cavity and the second resonant cavity are coupled to the bus waveguides 102 and 104, respectively.

[0045] Optionally, the first resonant cavity 101 and the second resonant cavity 105 have different physical cavity lengths; they have different free spectral ranges, and the vernier effect is generated in the frequency domain through the period difference, so that the reflection spectral peaks on both sides coincide at a specific wavelength, so as to achieve single longitudinal mode wavelength tuning with a large free spectral range.

[0046] Optionally, independent vernier tuning electrodes 106 and 108 are respectively disposed on both sides of the first resonant cavity 101 and the second resonant cavity 105. Utilizing the electro-optic effect of the thin film layer 402 material, a uniform refractive index tuning electric field is generated in the waveguide region, independently changing the effective refractive index of the two Fabry-Perot cavities, thereby achieving wide-range coordinated tuning of the center wavelength of the vernier reflection peak; phase-tuning electrodes 107 are distributed on both sides of the second bus waveguide 104 (they can also be disposed on both sides of the first bus waveguide 102). Figure 1 (The example shown is only set on both sides of the second bus waveguide 104) As a phase adjuster, it is used to finely adjust the longitudinal mode phase of the main lasing cavity, so that the longitudinal mode of the laser cavity is precisely synchronized with the vernier reflection peak after the superposition of the two Fabry-Perot resonators, and mode skipping tuning is achieved.

[0047] Those skilled in the art will understand that the broadband tunable laser provided in the above embodiments can be widely used in broadband tunable light sources, high side-mode suppression ratio lasers, and frequency modulated continuous wave (FMCW) lidar transmission systems.

[0048] The following is a detailed description of specific embodiments: Example

[0049] The thin film material used in this embodiment is thin-film lithium tantalate. The center wavelength of the Gaussian apodized Bragg grating is 1550 nm, and the grating coupling coefficient is... The grating period is 426nm, and the total number of periods is 200. For example... Figure 4 As shown, the grating exhibits broadband high-resistivity stopband characteristics, providing a high-quality reflection envelope for the side-coupled Fabry-Perot resonator. The optical field undergoes multi-beam interference between the front and rear gratings, forming a comb-shaped reflection spectrum. The effective physical cavity lengths of the first and second resonators are 1000 μm and 1020 μm, respectively, with a 20 μm difference achieved by controlling the length of the internal straight waveguide. Based on the group refractive index of approximately 2.2 of the thin-film lithium tantalate waveguide, the two Fabry-Perot cavities generate free spectral ranges corresponding to their respective physical cavity lengths. Taking the first Fabry-Perot cavity as an example, its reflection spectrum P1 is as follows... Figure 4 As shown in the middle red comb teeth; Figure 4 As shown, the difference between the two excites the vernier effect in the frequency domain. The vernier free spectrum range, directly determined by the cavity length difference, is approximately 53 nm.

[0050] Figure 5The reflectivity product spectrum of the first and second resonant cavities is also presented. Figure 5 It is known that due to the mismatch in the free spectral range of the two resonant cavities, physical alignment is achieved only at a specific center wavelength within the grating reflection envelope, forming a highly prominent coincident main peak. Furthermore, the suppression ratio with the adjacent highest-order sidelobe reaches 5.5 dB, ensuring stable single-mode output from a passive mechanism. In laser wavelength tuning, by applying a driving voltage to the vernier tuning electrodes distributed on the two resonant cavities, the effective refractive index of the waveguide is changed using the linear electro-optic effect of thin-film lithium tantalate, causing a translation of the comb-shaped reflection spectrum. This vernier effect drives the aforementioned coincident main peak to undergo a large-scale transition. Simultaneously, the phase-tuning electrodes located on the bus waveguide are responsible for finely compensating the overall longitudinal mode phase of the lasing main cavity, ensuring that the laser longitudinal mode always maintains strict synchronous movement with the vernier coincident main peak, thereby ultimately achieving a wide range of lasing wavelength switching.

[0051] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A broadband tunable laser based on heterogeneous integration, characterized in that, include: The system comprises a first bus waveguide, a second bus waveguide, a first resonant cavity, a second resonant cavity, and a heterogeneous integrated gain module. The first resonant cavity is coupled to the side of one end of the first bus waveguide to receive the optical signal coupled in from the first bus waveguide, and to resonate the light in the optical signal that meets the resonance condition of the first resonant cavity within the cavity, and then couple and reflect it to the first bus waveguide. The second resonant cavity is coupled to the side of one end of the second bus waveguide to receive the optical signal coupled in from the second bus waveguide, and to resonate the light in the optical signal that meets the resonance condition of the second resonant cavity within the cavity, and then couple and reflect it to the second bus waveguide. The two ends of the heterogeneous integrated gain module are coupled to the other ends of the first bus waveguide and the second bus waveguide, respectively, to receive the optical signals reflected by the first resonant cavity and the second resonant cavity, and to provide stimulated emission gain for the received optical signals, and then coupled back to the first bus waveguide and the second bus waveguide. One end face of the first or second bus waveguide is used to output the optical signal transmitted by the first or second resonant cavity as output light; wherein the first and second resonant cavities have different free spectral ranges, the first resonant cavity has a first reflection spectrum, and the second resonant cavity has a second reflection spectrum; the wavelength of the output light is determined by the main peak that coincides between the first and second reflection spectra.

2. The broadband tunable laser according to claim 1, characterized in that, The first reflection spectrum and the second reflection spectrum have at least partial overlap in the wavelength domain; The heterogeneous integrated gain module is also used to generate spontaneous emission to provide an initial optical signal; the wavelength of the initial optical signal covers at least a portion of the overlapping bands.

3. The broadband tunable laser according to claim 1 or 2, characterized in that, Also includes: First tuning electrode and / or second tuning electrode; The first tuning electrode is used to perform translation tuning on the first reflection spectrum; The second tuning electrode is used to perform translation tuning on the second reflection spectrum; The first tuning electrode and / or the second tuning electrode are used to achieve vernier effect tuning of the output light.

4. The broadband tunable laser according to claim 1, characterized in that, The heterogeneous integrated gain module includes: an injection electrode and an active waveguide; The injection electrode is used to inject charge carriers into the active waveguide. The active waveguide has its two ends coupled to the other ends of the first bus waveguide and the second bus waveguide, respectively, and is used to provide stimulated emission gain for the optical signal under the action of charge carriers and optical signal.

5. The broadband tunable laser according to claim 1, characterized in that, The first or second resonant cavity includes: two Bragg gratings and a straight waveguide, which is coupled to the side of one end of the corresponding bus waveguide through the straight waveguide; The straight waveguide is used to connect two Bragg gratings; The straight waveguide lengths of the first resonant cavity and the second resonant cavity are different.

6. The broadband tunable laser according to claim 5, characterized in that, The Bragg grating is a Gaussian apodized grating.

7. The broadband tunable laser according to claim 1, characterized in that, Also includes: Phase-modulating electrode; The phase-adjusting electrode is disposed above the first bus waveguide and / or the second bus waveguide, and is used to adjust the longitudinal mode phase of the total resonant cavity composed of the first resonant cavity, the first bus waveguide, the heterogeneous integrated gain module, the second bus waveguide, and the second resonant cavity, so that the longitudinal mode wavelength of the total resonant cavity is aligned with the main peak that coincides between the first reflection spectrum and the second reflection spectrum.

8. The broadband tunable laser according to any one of claims 1 to 7, characterized in that, The other end of the first bus waveguide and the other end of the second bus waveguide are thermally coupled to the heterogeneous integrated gain module in the vertical direction.

9. The broadband tunable laser according to any one of claims 1 to 7, characterized in that, The first bus waveguide, the second bus waveguide, the first resonant cavity, and the second resonant cavity are made of lithium tantalate or lithium niobate, and the heterogeneous integrated gain module is made of III-V group semiconductor material.

10. An application of the broadband tunable laser as described in any one of claims 1 to 9 in a broadband tunable light source, laser, and / or lidar emitting system.

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