Tunable resonant cavity and laser

Abstract

The embodiments of the present disclosure provide a tunable resonant cavity and a laser. The tunable resonant cavity includes: a microring, comprising a circular arc waveguide portion and a straight waveguide portion; a thermal module is provided on the straight waveguide portion for adjusting the refractive index of the microring; a thermal isolation groove, wherein the thermal isolation groove has a Bragg grating structure and is located on both sides of the thermal module; and a curved waveguide, comprising a first curved waveguide and a second curved waveguide, wherein the first curved waveguide and the second curved waveguide respectively have a first coupling region and a second coupling region with the circular arc waveguide portion.

Description

Technical Field

[0001] The present disclosure relates to the field of optoelectronic integrated devices, and in particular to a tunable resonant cavity and a laser. Background Art

[0002] Silicon photonics technology applies the core concepts of "replacing electricity with light" and "integration of optoelectronics and photonics" and has huge advantages in terms of functionality, power consumption, cost, packaging difficulty, reliability, and scalability. However, since silicon itself is an indirect bandgap semiconductor material with extremely low luminous efficiency, the integration of silicon-based light sources is a global problem that has not yet been fully solved.

[0003] With the increasing demand for ultra-high-speed coherent optical communication, lasers are playing an increasingly important role in silicon photonic integrated chips. Therefore, it is necessary to provide a narrow-linewidth laser with a tunable resonant cavity that breaks through integration. Summary of the Invention

[0004] In view of this, embodiments of the present disclosure provide a tunable resonant cavity and a laser.

[0005] To achieve the above objectives, the technical solution of the present disclosure is implemented as follows:

[0006] On the one hand, an embodiment of the present disclosure provides a tunable resonant cavity, comprising: a microring, comprising a circular arc waveguide portion and a straight waveguide portion; a thermal module is provided on the straight waveguide portion for adjusting the refractive index of the microring; a thermal isolation groove, wherein the thermal isolation groove has a Bragg grating structure and is located on both sides of the thermal module; and a curved waveguide, comprising a first curved waveguide and a second curved waveguide, wherein the first curved waveguide and the second curved waveguide respectively have a first coupling region and a second coupling region with the circular arc waveguide portion.

[0007] In some embodiments, the curved waveguide includes a curved portion, and the curvature of the curved portion is the same as the curvature of the circular arc waveguide portion.

[0008] In some embodiments, a distance between the curved portion of the curved waveguide and the circular arc waveguide portion is between 100 μm and 300 μm.

[0009] In some embodiments, the straight waveguide portion includes a straight waveguide core and a waveguide cladding, the waveguide cladding is used to form the thermal isolation groove; the thermal module is located above the straight waveguide core, and the thermal isolation groove is located on both sides of the thermal module and the straight waveguide core; and along the stacking direction of the thermal module and the straight waveguide core, the projection of the thermal isolation groove does not overlap with the thermal module and the straight waveguide core.

[0010] In some embodiments, the distance between the thermal isolation slot and the straight waveguide core is between 100 nm and 200 nm.

[0011] On the other hand, an embodiment of the present disclosure provides a laser, comprising: a light source module, a gain module, and a tunable resonant cavity according to any of the above embodiments, connected in sequence; the gain module is connected to the curved waveguide and is used to amplify the optical signal output by the light source module; the tunable resonant cavity is used to frequency-lock the optical signal output by the gain module and output an optical signal that meets the resonant frequency; the light source module is also used to reflect the optical signal that meets the resonant frequency, so that the gain module and the tunable resonant cavity achieve self-injection locking; an output module is coupled to the output part of the gain module and is used to output the self-injection-locked optical signal.

[0012] In some embodiments, the light source module includes: a pump light source and a first reflector; and the gain module is connected to the pump light source and the first reflector.

[0013] In some embodiments, a beam splitter is further included; the input end of the beam splitter is connected to the gain module, the first output end of the beam splitter is connected to the first curved waveguide, and the second output end of the beam splitter is connected to the second curved waveguide.

[0014] In some embodiments, the gain module is connected to the second curved waveguide; and a second reflector is provided at one end of the first curved waveguide for reflecting an optical signal entering the first curved waveguide.

[0015] In some embodiments, the output module includes a first waveguide, a monitor, and an output coupler; the first waveguide is coupled to the output portion of the gain module, one end of the first waveguide is provided with a monitor for monitoring the optical signal entering the first waveguide; the other end of the first waveguide is provided with the output coupler for outputting the self-injection locked optical signal.

[0016] The disclosed embodiments provide a tunable resonant cavity and a laser. The tunable resonant cavity includes: a microring comprising a circular arc waveguide portion and a straight waveguide portion; a thermal module disposed on the straight waveguide portion for adjusting the refractive index of the microring; a thermal isolation slot having a Bragg grating structure and located on either side of the thermal module; and a curved waveguide comprising a first curved waveguide and a second curved waveguide, the first curved waveguide and the second curved waveguide respectively having a first coupling region and a second coupling region with the circular arc waveguide portion. The disclosed embodiments improve the thermal tuning efficiency of the tunable resonant cavity and reduce power consumption by disposing the thermal module on the straight waveguide portion of the microring and thermal isolation slots having a Bragg grating structure on either side of the thermal module. Furthermore, the resonance between the microring and the thermal isolation slot improves the quality factor of the tunable resonant cavity and provides a narrower linewidth optical signal. Furthermore, the provision of thermal isolation slots having a Bragg grating structure on either side of the straight waveguide portion provides greater design flexibility and room for performance optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic structural diagram of a tunable resonant cavity provided in an embodiment of the present disclosure;

[0018] Figure 2 Provided for the embodiments of the present disclosure Figure 1 The reflection spectrum of the micro-ring in the tunable resonant cavity and the reflection spectrum of the thermal isolation slot;

[0019] Figure 3 Provided for the embodiments of the present disclosure Figure 1 A partial cross-sectional view of the tunable resonant cavity along line AA';

[0020] Figure 4 A schematic diagram of the structure of a laser provided in an embodiment of the present disclosure Figure 1 ;

[0021] Figure 5 A schematic diagram of the structure of a laser provided in an embodiment of the present disclosure Figure 2 ;

[0022] Figure 6 A schematic diagram of the structure of a laser provided in an embodiment of the present disclosure Figure 3 . DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present disclosure in conjunction with the embodiments of the present disclosure and the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present disclosure.

[0024] In the following description, numerous specific details are provided to provide a more thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure can be practiced without one or more of these details. In other instances, certain technical features known in the art are not described to avoid confusion with the present disclosure; that is, all features of actual embodiments are not described herein, nor are well-known functions and structures described in detail.

[0025] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0026] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to, or coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, directly adjacent to, directly connected to, or directly coupled to" another element or layer, there may be no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part. However, when the second element, component, region, layer, or part is discussed, it does not necessarily mean that the first element, component, region, layer, or part exists in the present disclosure.

[0027] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, the spatially relative terms are intended to include different orientations of the device in use and operation. For example, if the device in the drawings is flipped, then the elements or features described as "under the other elements" or "under it" or "under it" will be oriented as "on" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0028] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present disclosure. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0029] In order to fully understand the present disclosure, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present disclosure. The preferred embodiments of the present disclosure are described in detail below. However, in addition to these detailed descriptions, the present disclosure may also have other implementation methods.

[0030] It should be noted that for ease of description, various directions that may be used in the following description are first defined. The stacking direction of the thermal module and the straight waveguide core is defined as the vertical direction (i.e., the Z direction in the figure). In a plane perpendicular to the Z direction, intersecting X and Y directions are defined. The X direction can be perpendicular to the straight waveguide portion, and the Y direction can be parallel to the straight waveguide portion. The X direction, Y direction, and Z direction can be perpendicular to each other.

[0031] Figure 1 A schematic diagram of the structure of a tunable resonant cavity provided in an embodiment of the present disclosure. Figure 1 As shown, the tunable resonant cavity 100 includes: a microring 110, including arc waveguide parts 111 and 112 and a straight waveguide part 113; a thermal module 120 is provided on the straight waveguide part 113 for adjusting the refractive index of the microring 110; a thermal isolation groove 130, which has a Bragg grating structure and is located on both sides of the thermal module 120; and a curved waveguide 140, including a first curved waveguide 141 and a second curved waveguide 142, which respectively have a first coupling region 151 and a second coupling region 152 with the arc waveguide parts 111 and 112.

[0032] It's important to note that in a resonant cavity containing a microring, the optical path difference of a light signal with a wavelength of λ as it propagates around the microring is an integer multiple of λ. This constructive interference of the light signal within the microring strengthens the light signal with wavelength λ, a phenomenon known as optical resonance. Wavelength λ is also the resonant wavelength of the microring. This resonant wavelength can be altered by adjusting the refractive index of the microring or by adjusting the radius of the circular waveguide or the length of the straight waveguide within the microring, allowing light signals of different wavelengths to resonate within the microring.

[0033] In some embodiments, an optical signal is transmitted through the first curved waveguide 141 and / or the second curved waveguide 142 , wherein a portion of the optical signal is coupled into the microring 110 through the first coupling region 151 and / or the second coupling region 152 for transmission to generate resonance, and the optical signal not coupled into the microring 110 can be diverged through the diverging port 1411 and / or the diverging port 1421 .

[0034] In some embodiments, the thermal isolation trench 130 comprises a Bragg grating structure. This Bragg grating structure has a periodically varying refractive index and exhibits a high reflectivity in a wavelength region (bandwidth) near a specific wavelength. This means that optical signals with a specific wavelength (i.e., optical signals that meet the Bragg condition) receive the strongest optical feedback at the Bragg grating. Light waves within a grating period are reflected by the Bragg grating structure. The optical signals reflected from each grating plane of the Bragg grating structure gradually accumulate, forming a Bragg peak. The abscissa center of the peak is denoted as the central wavelength of the Bragg grating structure, which is determined by the grating parameters of the Bragg grating structure. By adjusting the grating parameters of the thermal isolation trench 130 so that the reflection wavelength of the thermal isolation trench 130 (a specific wavelength that satisfies the Bragg condition) matches the resonant wavelength of the microring 110, the resonance of the optical signal that meets the Bragg condition in the microring 110 is significantly enhanced, further enhancing the narrowband response characteristics of the tunable resonant cavity 100 and achieving a narrower linewidth and a higher quality factor. Optical signals that do not meet the Bragg condition will partially transmit or leave the microring 110 with a weaker reflection intensity due to the weak reflection effect of the thermal isolation trench 130 having the Bragg grating structure. Furthermore, when the reflection wavelength of the thermal isolation trench 130 matches the resonant wavelength of the microring 110, the resonance effect between the thermal isolation trench and the microring makes the resonance peak generated by the optical signal passing through the tunable resonant cavity 100 sharper, thereby enhancing the quality factor of the tunable resonant cavity 100.

[0035] like Figure 1As shown, a thermal module 120 is disposed on the straight waveguide portion 113 of the microring 110, and thermal isolation slots 130 are located on both sides of the thermal module 120. By adjusting the temperature of the thermal module 120, a thermo-optical effect can be induced on the straight waveguide portion 113, changing the refractive index of the microring 110. Since the free spectral range (FSR) of the microring 110 is related to the refractive index of the microring 110, the FSR of the microring 110 can be adjusted, thereby achieving frequency tuning and linewidth narrowing of the tunable resonant cavity 100. Furthermore, the reflectivity and reflection wavelength of the thermal isolation slot 130 can be adjusted, thereby affecting the feedback light intensity of the Bragg grating. When the feedback light intensity is adjusted to the optimal level, the noise suppression effect is maximized, i.e., the linewidth is minimized. In short, by adjusting the temperature of the thermal module 120, the resonant wavelength of the microring 110 and the reflection wavelength of the thermal isolation slot 130 can be simultaneously adjusted, achieving synchronized selection of the optical signal wavelength by the microring 110 and the thermal isolation slot 130, thereby achieving highly efficient wavelength tuning. At the same time, the thermal isolation grooves 130 located on both sides of the thermal module 120 can reduce the dissipation of heat energy generated by the thermal module 120 into the surrounding environment and concentrate the heat energy in the straight waveguide part, thereby improving the thermal tuning efficiency of the tunable resonant cavity 100, optimizing the thermal isolation effect, reducing thermal crosstalk and reducing energy loss.

[0036] like Figure 1 As shown, the thermal module 120 includes a thermal resistor 121 and an electrode 122 . The temperature of the thermal resistor 121 can be changed by controlling the current applied to the thermal resistor 121 by the electrode 122 , thereby achieving the purpose of adjusting the temperature of the thermal module 120 .

[0037] In some embodiments, the thermal isolation groove 130 having a Bragg grating structure is disposed on the straight waveguide portion 113 of the microring 110 , which can have higher design flexibility and performance optimization space compared to designing the thermal isolation groove having a Bragg grating structure on the arc waveguide portion of the microring.

[0038] In some embodiments, a λ / 4 phase shift is introduced in the middle of the Bragg grating structure of the thermal isolation slot 130, so that when the optical signal passes through the region where the λ / 4 phase shift is introduced in the thermal isolation slot 130, the phase of the optical signal will produce a π / 2 phase shift. At this time, the reflected light and the incident light undergo destructive interference in the central region of the grating, forming a standing wave. The superposition of the standing waves in the center of the grating is conducive to achieving better single longitudinal mode resonance, further improving the quality factor of the tunable resonant cavity 100.

[0039] Figure 2 Provided for the embodiments of the present disclosure Figure 1 The reflection spectrum of the micro-ring in the tunable resonant cavity and the reflection spectrum of the thermal isolation slot. Figure 2As shown, the reflection spectrum 210 of the microring 110 has multiple resonance peaks. Due to the introduction of a λ / 4 phase shift in the middle of the thermal isolation slot 130, the grating power on both sides of the phase shift region decays exponentially, resulting in a reflection spectrum 220 on both sides of an extremely narrow peak 221. Therefore, the reflection spectrum 220 has an extremely narrow peak 221 in the phase shift region (the center of the grating), that is, the reflection spectrum 220 has an extremely narrow peak 221 at the center of the spectrum. By designing the Bragg grating period parameters of the thermal isolation slot 130, the wavelength of the extremely narrow peak 221 coincides with the wavelength of a resonance peak in the reflection spectrum 210, that is, the extremely narrow peak 221 and the resonance peak 211 have a resonant wavelength 230. This allows the microring 110 and the thermal isolation slot 130 to achieve the strongest resonance effect.

[0040] In some embodiments, the radius of the arc waveguide portion in microring 110 can be set between 100 μm and 200 μm, and the length of the straight waveguide portion can be set to approximately 500 μm. In this case, microring 110 has a good quality factor. It should be noted that the length of the straight waveguide portion is substantially the same as the length of the thermal isolation slot.

[0041] In some embodiments, multiple microrings may be included between the first curved waveguide and the second curved waveguide. The multiple microrings may be arranged along either the X-direction or the Y-direction. Leveraging the Vernier effect generated by the multiple microrings, the tuning range of the tunable resonant cavity can be significantly improved. It should be noted that both straight waveguide portions of the microring may be provided with a thermal module and a thermal isolation slot having a Bragg grating structure, and at least one of the multiple microrings may be provided with a thermal module and a thermal isolation slot having a Bragg grating structure.

[0042] It should be noted that the waveguide material selected for the microring 110 , the first curved waveguide 141 , and the second curved waveguide 142 may include at least one of silicon, silicon nitride, or lithium niobate.

[0043] In some embodiments, the curved waveguide includes a curved portion having a curvature that is the same as the curvature of the arc waveguide portion.

[0044] In some embodiments, as Figure 1As shown, the first curved waveguide 141 includes a curved portion 143, whose curvature is the same as that of the arc waveguide portion 111, so that the curved portion 143 and the arc waveguide portion 111 form a concentric circular arc. The second curved waveguide 142 includes a curved portion 144, whose curvature is the same as that of the arc waveguide portion 112, so that the curved portion 144 and the arc waveguide portion 112 form a concentric circular arc. By designing the curved portions 143 and 144 to conform to the shape of the arc waveguide portion in the microring 110, the first coupling region 151 and the second coupling region 152 can be enlarged, achieving efficient coupling of optical signals. In this way, the first and second curved waveguides 141 and 142, excluding the coupling regions, can be designed to be shorter, thereby reducing chip area while achieving a larger coupling bandwidth and lower insertion loss.

[0045] Preferably, the curvatures of the curved portion 143, the curved portion 144, the arc waveguide portion 111, and the arc waveguide portion 112 are all the same, the lengths of the curved portion 143 and the curved portion 144 are the same, and the lengths of the arc waveguide portion 111 and the arc waveguide portion 112 are the same, so that the tunable resonant cavity 100 has an axially symmetrical structure in the X direction.

[0046] In some embodiments, a distance between the curved portion and the circular arc waveguide portion of the curved waveguide is between 100 μm and 300 μm.

[0047] In some embodiments, the first coupling region 151 and the second coupling region 152 are used to achieve coupling and decoupling of optical signals. By setting the spacing between the curved portion 143 and the arc waveguide portion 111 to between 100 μm and 300 μm, and setting the spacing between the curved portion 144 and the arc waveguide portion 112 to between 100 μm and 300 μm, the first coupling region 151 and the second coupling region 152 can have a good coupling coefficient, and the coupling coefficient can be controlled to be around 0.1.

[0048] It should be noted that the radius of the curved portion 143 can be the sum of the radius of the arc waveguide portion 111 and the distance between the two, and the radius of the curved portion 144 can be the sum of the radius of the arc waveguide portion 112 and the distance between the two, so that the distance between the curved portion and the corresponding arc waveguide portion can be equal everywhere.

[0049] In some embodiments, the straight waveguide portion includes a straight waveguide core and a waveguide cladding, the waveguide cladding is used to form a thermal isolation groove; the thermal module is located above the straight waveguide core, and the thermal isolation groove is located on both sides of the thermal module and the straight waveguide core; and along the stacking direction of the thermal module and the straight waveguide core, the projection of the thermal isolation groove does not overlap with the thermal module and the straight waveguide core.

[0050] Figure 3 Provided for the embodiments of the present disclosure Figure 1 A partial cross-sectional view of the tunable resonant cavity along line AA'. Figure 1 and Figure 3 As shown, the straight waveguide portion 113 is located on the substrate 300. The straight waveguide portion 113 includes a straight waveguide core 310 and a waveguide cladding 320. The thermal module 120 includes a thermal resistor 121 and an electrode 122. The thermal resistor 121 is located above the straight waveguide core 310. Along the stacking direction (Z direction) of the thermal module and the straight waveguide core, the projection of the thermal resistor 121 overlaps with the projection of the straight waveguide core 310. Preferably, the projection of the thermal resistor 121 in the Z direction can cover the projection of the straight waveguide core 310 in the Z direction. The electrode 122 is provided on the thermal resistor 121. By controlling the current applied to the thermal resistor 121 by the electrode 122, the temperature of the thermal resistor 121 is controlled.

[0051] like Figure 3 As shown, the waveguide cladding 320 includes a first portion 320a and a second portion 320b, wherein the first portion 320a and the second portion 320b can be manufactured by the following steps: providing an initial structure including a waveguide cladding material located on a substrate 300 and a straight waveguide core 310 embedded in the waveguide cladding material; then etching a portion of the waveguide cladding material located above the straight waveguide core 310 along the Z direction to form a first groove, depositing a conductive material in the first groove to form a thermal resistor 121, and forming an electrode 122 on the thermal resistor 121; finally, etching the waveguide cladding material on both sides of the straight waveguide core to form the first portion 320a and the second portion 320b, and the thermal isolation groove 130 includes the second portion 320b of the waveguide cladding 320 and a groove between the first portion 320a and the second portion 320b. The thermal isolation groove 130 having the Bragg grating structure is formed by etching the waveguide cladding material, thereby avoiding directly etching the straight waveguide core 310 to form the Bragg grating structure, reducing the waveguide loss and improving the quality factor of the tunable resonant cavity 100 .

[0052] In some embodiments, the distance between the thermal isolation slot and the straight waveguide core is between 100 nm and 200 nm.

[0053] In some embodiments, the distance d1 between the thermal isolation slot 130 and the straight waveguide core 310 is between 100 nm and 200 nm. In this case, the thermal isolation slot 130 provides excellent thermal insulation, ensuring efficient adjustment of the refractive index of the straight waveguide portion 113 and achieving good resonance. It should be noted that the distance between the thermal isolation slot on the left and the straight waveguide core is the same as the distance between the thermal isolation slot on the right, i.e., the thermal isolation slots on both sides are arranged at equal distances from the straight waveguide core.

[0054] In some embodiments, the distance d2 between the thermal module 120 and the straight waveguide core 310 is between 1 μm and 3 μm, that is, the thickness of the waveguide cladding material between the thermal resistor 121 and the straight waveguide core 310 is between 1 μm and 3 μm. At this time, the thermal field generated by the thermal resistor 121 has a good coverage range of the straight waveguide core 310, avoiding uneven thermal field coverage and adverse effects on the refractive index adjustment of the straight waveguide part.

[0055] Figure 4 A schematic diagram of the structure of a laser provided in an embodiment of the present disclosure Figure 1 .like Figure 4 As shown, the laser includes: a light source module 410, a gain module 420 and a tunable resonant cavity 100 in any of the above embodiments connected in sequence; the gain module 420 is connected to the curved waveguide and is used to amplify the optical signal output by the light source module 410; the tunable resonant cavity 100 is used to frequency-lock the optical signal output by the gain module 420 and output an optical signal that meets the resonant frequency; the light source module 410 is also used to reflect the optical signal that meets the resonant frequency, so that the gain module 420 and the tunable resonant cavity 100 achieve self-injection locking; an output module 430 is coupled to the output part 422 of the gain module 420 and is used to output the self-injection-locked optical signal.

[0056] like Figure 4 As shown, the gain module 420 includes a gain part 421 and an output part 422. The light source module 410 outputs an initial light signal to the gain part 421. After the initial light signal enters the gain part 421, it stimulates the optical amplification effect of the gain part 421, so that the gain part 421 amplifies the initial light signal and transmits it to the curved waveguide through the output part 422 of the gain module 420. The light signal output by the gain module 420 is coupled into the microring through the curved waveguide, so that the light signal meeting the resonant frequency of the microring is frequency-locked in the tunable resonant cavity 100. After frequency locking, the light signal returns to the light source module 410 through the gain module 420 and is reflected back to the tunable resonant cavity 100 by the light source module 410. In this way, a stable external cavity structure can be formed in the laser, which can improve the coherence of the laser. Furthermore, when the optical signal returning from the light source module 410 to the tunable resonant cavity 100 matches the resonant wavelength of the microring and the thermal isolation slot, the laser achieves self-injection locking, forming a self-injection feedback system. The microring resonant cavity and the thermal isolation slot are used to synchronously select and tune the wavelength of the optical signal, locking the resonant wavelength of the tunable resonant cavity to the gain peak of the gain section. This generates a self-injection-locked optical signal, achieving tunable narrow-linewidth laser light. When the self-injection-locked optical signal is transmitted to the output section 422 of the gain module 420, it can be coupled to the output module 430 and output as laser light.

[0057] In some embodiments, the gain section 421 may be an erbium-doped waveguide formed by implanting erbium ions into the waveguide helix through ion implantation. The gain section 421 is also used to provide a gain medium for the tunable resonant cavity to achieve good laser resonance.

[0058] It should be noted that the waveguide structures of the gain part 421 and the output part 422 of the gain module 420 may be different. For example, the gain part 421 may be a spiral waveguide, and the output part 422 may be a straight waveguide.

[0059] It should be noted that the frequency and wavelength of the optical signal are in an inverse relationship. Therefore, the optical signal that meets the resonant frequency of the microring can be understood as the optical signal that meets the resonant wavelength of the microring. Since the resonant wavelength of the microring is the same as the reflection wavelength of the thermal isolation groove, the optical signal meets the resonant wavelength of the microring and the thermal isolation groove.

[0060] In some embodiments, the light source module 410 includes: a pump light source 411 and a first reflector 412 ; and the gain module 420 is connected to the pump light source 411 and the first reflector 412 .

[0061] like Figure 1 As shown, pump light source 411 is used to output an initial optical signal to gain module 420 to stimulate the optical amplification effect of gain section 421. First reflector 412 is used to reflect the frequency-locked optical signal back into tunable resonant cavity 100, achieving a stable external cavity structure. In addition, first reflector 412 can also enhance the transmission efficiency of the optical signal and reduce the attenuation of the optical signal.

[0062] In some embodiments, the light source module 410 further includes a wavelength division multiplexer 413, which includes two input terminals and one output terminal. The two input terminals of the wavelength division multiplexer 413 are respectively connected to the pump light source 411 and the first reflector 412, and the output terminal of the wavelength division multiplexer 413 is connected to the gain module 420. In addition, the wavelength division multiplexer 413 allows multiple optical signals to be transmitted in parallel. Therefore, the wavelength division multiplexer 413 can achieve efficient transmission of the initial optical signal output by the pump light source 411, the optical signal reflected by the first reflector 412, the optical signal returned by the tunable resonant cavity 100, and the laser light, thereby avoiding signal crosstalk.

[0063] In some embodiments, the pump light source 411 may be an on-chip grating structure having a pump wavelength, and the light source is integrated onto the grating by flip-sticking or bonding to form the pump light source.

[0064] In some embodiments, the output module 430 includes a first waveguide 431, a monitor 432, and an output coupler 433; the first waveguide 431 is coupled to the output portion 422 of the gain module 420, and a monitor 432 is provided at one end of the first waveguide 431 for monitoring the optical signal entering the first waveguide 431; an output coupler 433 is provided at the other end of the first waveguide 431 for outputting a self-injection-locked optical signal.

[0065] like Figure 4 As shown, first waveguide 431 is coupled to output portion 422 of gain module 420. Monitor 432 is used to monitor the optical signal coupled into first waveguide 431. Specifically, it is used to monitor the parameters of the optical signal entering first waveguide 431 in real time to monitor the tuning state of the laser and ensure the stability and accuracy of the final output optical signal. Output coupler 433 serves as the output end of the laser and is used to achieve stable output of the self-injection locking signal.

[0066] Figure 5 A schematic diagram of the structure of a laser provided in an embodiment of the present disclosure Figure 2 .like Figure 5 As shown, the laser further includes a beam splitter 510 ; the input end of the beam splitter 510 is connected to the gain module 420 , the first output end 511 of the beam splitter 510 is connected to the first curved waveguide 141 , and the second output end 512 of the beam splitter 510 is connected to the second curved waveguide 142 .

[0067] like Figure 5 As shown, the optical signal output by the gain module 420 is divided into two optical signals by the beam splitter 510. The optical signal output by the first output end 511 is coupled into the microring through the first curved waveguide 141 for frequency locking, and the optical signal output by the second output end 512 is coupled into the microring through the second curved waveguide 142 for frequency locking.

[0068] Figure 6 A schematic diagram of the structure of a laser provided in an embodiment of the present disclosure Figure 3 .like Figure 6 As shown, the gain module 420 is connected to the second curved waveguide 142 ; a second reflector 610 is provided at one end of the first curved waveguide 141 for reflecting the optical signal entering the first curved waveguide 141 .

[0069] like Figure 6As shown, the frequency-locked optical signal is reflected back into the tunable resonant cavity 100 not only through the first reflector 412 but also through the second reflector 610. This creates a stable external cavity structure within the laser, improving the coherence of the laser. When the optical signal returning from the first reflector 412 and the second reflector 610 to the tunable resonant cavity 100 matches the resonant wavelength of the microring and the thermal isolation slot, the laser achieves dual-reflection self-injection locking, generating a self-injection-locked optical signal and outputting a tunable narrow-linewidth laser. The first and second reflectors not only reflect the optical signal but also enhance its transmission efficiency and reduce its attenuation.

[0070] In some embodiments, the gain module is connected to the first curved waveguide, and a second reflector is disposed at one end of the second curved waveguide.

[0071] It should be noted that this disclosure Figure 1 、 Figures 3 to 6 Parts not marked with reference numerals may be shared.

[0072] It should be noted that the above description of the laser is similar to the description of the tunable resonant cavity embodiment described above, and has similar beneficial effects as the tunable resonant cavity embodiment. For any technical details not disclosed in the laser embodiment of this disclosure, please refer to the description of the tunable resonant cavity embodiment of this disclosure for understanding.

[0073] The disclosed embodiments provide a tunable resonant cavity and a laser. The tunable resonant cavity includes: a microring including a circular arc waveguide portion and a straight waveguide portion; a thermal module disposed on the straight waveguide portion for adjusting the refractive index of the microring; a thermal isolation slot having a Bragg grating structure and located on either side of the thermal module; and a curved waveguide including a first curved waveguide and a second curved waveguide, the first curved waveguide and the second curved waveguide respectively having a first coupling region and a second coupling region with the circular arc waveguide portion. The disclosed embodiments improve the thermal tuning efficiency of the tunable resonant cavity and reduce power consumption by disposing the thermal module on the straight waveguide portion of the microring and disposing thermal isolation slots having a Bragg grating structure on either side of the thermal module. Furthermore, the resonance phenomenon between the microring and the thermal isolation slot improves the quality factor of the tunable resonant cavity and provides a narrower linewidth optical signal. Furthermore, disposing the thermal isolation slots having a Bragg grating structure on either side of the straight waveguide portion provides greater design flexibility and room for performance optimization.

[0074] It should be understood that “one embodiment” or “an embodiment” mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present disclosure. Therefore, “in one embodiment” or “in an embodiment” appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in the various embodiments of the present disclosure, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present disclosure. The serial numbers of the embodiments of the present disclosure are for description only and do not represent the advantages and disadvantages of the embodiments.

[0075] The above description is only a preferred embodiment of the present disclosure and does not limit the patent scope of the present disclosure. All equivalent structural transformations made by using the contents of the present disclosure and the drawings under the inventive concept of the present disclosure, or direct / indirect application in other related technical fields are included in the patent protection scope of the present disclosure.

Claims

1. A tunable resonant cavity, characterized in that: include: A micro-ring, comprising a circular-arc waveguide portion and a straight waveguide portion; A thermal module is provided on the straight waveguide portion for adjusting the refractive index of the microring; a thermal isolation groove having a Bragg grating structure and located on both sides of the thermal module; The curved waveguide includes a first curved waveguide and a second curved waveguide, wherein the first curved waveguide and the second curved waveguide respectively have a first coupling region and a second coupling region with the circular arc waveguide portion.

2. The tunable resonant cavity according to claim 1, characterized in that: The curved waveguide includes a curved portion, and a curvature of the curved portion is the same as a curvature of the circular arc waveguide portion.

3. The tunable resonant cavity according to claim 1, wherein: The distance between the curved portion of the curved waveguide and the arc waveguide portion is between 100 μm and 300 μm.

4. The tunable resonant cavity according to claim 1, wherein: The straight waveguide portion includes a straight waveguide core and a waveguide cladding, and the waveguide cladding is used to form the thermal isolation slot; The thermal module is located above the straight waveguide core, and the thermal isolation groove is located on both sides of the thermal module and the straight waveguide core; and along the stacking direction of the thermal module and the straight waveguide core, the projection of the thermal isolation groove does not overlap with the thermal module and the straight waveguide core.

5. The tunable resonant cavity according to claim 4, characterized in that: The distance between the thermal isolation groove and the straight waveguide core is between 100 nm and 200 nm.

6. A laser, characterized in that include: A light source module, a gain module and a tunable resonant cavity according to any one of claims 1 to 5 connected in sequence; The gain module is connected to the curved waveguide and is used to amplify the optical signal output by the light source module; The tunable resonant cavity is used to frequency-lock the optical signal output by the gain module and output an optical signal meeting the resonant frequency; The light source module is further configured to reflect the optical signal meeting the resonant frequency, so that the gain module and the tunable resonant cavity achieve self-injection locking; An output module is coupled to the output portion of the gain module and is configured to output the self-injection locked optical signal.

7. The laser according to claim 6, characterized in that The light source module includes: a pump light source and a first reflector; The gain module is connected to the pump light source and the first reflector.

8. The laser according to claim 6, characterized in that Also included is a beam splitter; The input end of the beam splitter is connected to the gain module, the first output end of the beam splitter is connected to the first curved waveguide, and the second output end of the beam splitter is connected to the second curved waveguide.

9. The laser according to claim 6, characterized in that The gain module is connected to the second curved waveguide; A second reflector is provided at one end of the first curved waveguide for reflecting the optical signal entering the first curved waveguide.

10. The laser according to claim 6, characterized in that The output module includes a first waveguide, a monitor and an output coupler; The first waveguide is coupled to the output part of the gain module. A monitor is provided at one end of the first waveguide for monitoring the optical signal entering the first waveguide. The output coupler is provided at the other end of the first waveguide for outputting the self-injection locked optical signal.

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