Resonance module, silicon-based external cavity chip, laser and laser radar

Abstract

A resonance module, a silicon-based external cavity chip (100), a laser and a laser radar. The resonance module comprises a plurality of main resonant cavities and at least one auxiliary resonant cavity (150). The main resonant cavities and the auxiliary resonant cavity (150) are all tunable micro-ring resonant cavities; the plurality of main resonant cavities are sequentially cascaded by means of connecting modules (180) to form a cascade structure, and the vernier effect can be achieved by two adjacent main resonant cavities; and when the auxiliary resonant cavity (150) matching one main resonant cavity exists, the matching main resonant cavity and auxiliary resonant cavity (150) are coupled to expand the free spectral range of the main resonant cavity. According to the provided resonance module, silicon-based external cavity chip (100), laser and laser radar, the tunable range of a laser for a laser radar can be expanded, and the scanning angle of the laser radar can be enlarged.

Description

Resonance modules, silicon-based external cavity chips, lasers, and lidars

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 30, 2023, with application number 202310799150.2 and application name “Resonance module, silicon-based external cavity chip, laser and lidar”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the field of laser radar technology, and in particular relates to a resonance module, a silicon-based external cavity chip, a laser and a laser radar. Background Art

[0003] Currently, external cavity semiconductor lasers are increasingly widely used, and there are two main solutions for their implementation: one is an external cavity structure formed by discrete components such as etalons and diffraction gratings, and the other is a quasi-monolithic integrated external cavity structure based on silicon-based photonic chips. Among them, although the diffraction grating external cavity laser has a wide tuning range and extremely narrow linewidth, it is large in size, difficult to align the optical path, complex packaging, and low mechanical tuning efficiency, which will reduce the reliability of the laser to a certain extent. The silicon-based photonic chip external cavity narrow linewidth semiconductor laser integrates a gain chip with a quasi-monolithic silicon-based external cavity chip. It combines the wide tuning and narrow linewidth characteristics of the external cavity structure with the low power consumption and high reliability of the monolithic integrated structure.

[0004] Among them, the wavelength tunable range is a major advantage of silicon-based external cavity lasers, which is usually wider than other types of integrated lasers. Most of the current silicon-based external cavity lasers can cover the communication C-band range (1525nm-1565nm), while also maintaining a high side mode suppression ratio and a narrow linewidth, which is of course the basic requirement for tunable lasers in today's optical communication systems. However, with the recent rapid development of technologies such as optical phased arrays (OPA, Optical Phased Array), there is a demand for a wider tunable range for on-chip integrated lasers. Today's silicon-based external cavity lasers still need to further expand their tunable range while maintaining a narrow linewidth and high side mode suppression ratio.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to provide a resonant module, a silicon-based external cavity chip, a laser and a lidar, aiming to further expand the tunable range of the laser used in the lidar.

[0007] The present invention is implemented as follows: in a first aspect, a resonance module is provided, comprising a plurality of main resonant cavities and at least one auxiliary resonant cavity, wherein the main resonant cavities and the auxiliary resonant cavities are both tunable microring resonant cavities; the plurality of main resonant cavities are sequentially cascaded through a connection module to form a cascade structure, and a vernier effect can be formed between two adjacent main resonant cavities; when the main resonant cavity has a matching auxiliary resonant cavity, the matching main resonant cavity and the auxiliary resonant cavity are coupled so that the free spectrum range of the main resonant cavity is expanded.

[0008] In some embodiments, the cascade structure is a two-stage cascade structure, including a first main resonant cavity and a second main resonant cavity; the auxiliary resonant cavity is provided with a, which is matched with the first main resonant cavity; wherein there is a difference between the cavity length of the first main resonant cavity and the cavity length of the second main resonant cavity, and the cavity length of the first main resonant cavity and the cavity length of the second main resonant cavity are both integer multiples of the difference; the free spectrum range of the auxiliary resonant cavity is twice the free spectrum range of the first main resonant cavity.

[0009] In some embodiments, the cavity length of the auxiliary resonant cavity is 1 / 2 of the cavity length of the first main resonant cavity.

[0010] In some embodiments, the cascade structure is a cascade structure formed by sequentially cascading three or more main resonant cavities, and the difference in cavity lengths between every two adjacent main resonant cavities is different.

[0011] In some embodiments, when the cascade structure is an N-stage cascade structure, N is an integer greater than 1, and the resonance module receives two input light beams from the outside; one of the input light beams enters the resonance module through the input end of the first-stage main resonant cavity, and after passing through N main resonant cavities in sequence, is coupled out of the resonance module from the download end of the N-stage main resonant cavity; the other input light beam enters the resonance module through the download end of the N-stage main resonant cavity, and after passing through N main resonant cavities in sequence, is coupled out of the resonance module from the input end of the first-stage main resonant cavity.

[0012] In some embodiments, the connection module includes: a waveguide; or a combination structure of a waveguide and one of the main resonant cavities.

[0013] In a second aspect, a silicon-based external cavity chip is provided, comprising an input coupler, a directional coupler, a resonant module, and an output coupler; wherein the resonant module is the resonant module provided in each of the above embodiments;

[0014] Wherein, the input coupler is used to couple the optical signal provided by the external light source into the silicon-based external cavity chip;

[0015] The directional coupler receives the optical signal and provides it to the resonance module. The resonance module selects the optical signal and couples the selected optical signal out through the directional coupler and the output coupler in sequence.

[0016] In some embodiments, the directional coupler is a 2×2 directional coupler;

[0017] Wherein, after the optical signal is received by the first end of the directional coupler, it is split into two input light beams in the directional coupler; one of the input light beams is sequentially coupled into the resonance module through the second end of the directional coupler and the first end of the resonance module, and after passing through the cascade structure of the resonance module, it is coupled into the directional coupler through the second end of the resonance module and the third end of the directional coupler, and is provided to the output coupler by the fourth end of the directional coupler; the other input light beam is sequentially coupled into the resonance module through the third end of the directional coupler and the second end of the resonance module, and after passing through the cascade structure of the resonance module, it is coupled into the directional coupler through the first end of the resonance module and the second end of the directional coupler, and is provided to the output coupler by the fourth end of the directional coupler.

[0018] In some embodiments, the silicon-based external cavity chip further includes a phase shifter connected between the input coupler and the first end of the directional coupler.

[0019] In a third aspect, a silicon-based external cavity chip is provided, comprising an input coupler, a resonance module, and a Sagnac ring; the resonance module is the resonance module provided in each of the above embodiments;

[0020] Wherein, the input coupler is used to couple the optical signal provided by the external light source into the silicon-based external cavity chip;

[0021] A first end of the resonance module is coupled to the input coupler through a waveguide, and a second end of the resonance module is coupled to the Sagnac ring.

[0022] In a fourth aspect, a silicon-based external cavity laser is provided, comprising a light source and the silicon-based external cavity chip provided by the above embodiments, wherein the light source is used to provide an optical signal for the silicon-based external cavity chip.

[0023] In a fifth aspect, a laser radar is provided, comprising a laser module, a transmitting module, a detecting module, a detecting module and a data processing module, wherein the laser module comprises the silicon-based external cavity laser provided in the above embodiment.

[0024] The technical effect of the technical solution of the present application compared to the prior art is as follows: the resonance module provided by the first aspect is adopted, including multiple main resonant cavities and at least one auxiliary resonant cavity, the multiple main resonant cavities are cascaded in sequence through the connection module to form a cascade structure, and a vernier effect can be formed between two adjacent main resonant cavities; when there is a matching auxiliary resonant cavity in the main resonant cavity, the free spectrum range of the main resonant cavity can be expanded by coupling the matching main resonant cavity and the auxiliary resonant cavity, and the vernier effect of the cascade structure greatly expands the tunable range of the laser using the resonance module provided by the embodiment of the present invention. At the same time, in the silicon-based external cavity laser circuit, the introduction of the auxiliary resonant cavity coupled with the main resonant cavity can maintain the narrow linewidth and tunable characteristics of the silicon-based external cavity.

[0025] It can be understood that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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 embodiments of the present invention or the description of the prior art. 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.

[0027] FIG1 is a schematic structural diagram of a silicon-based external cavity laser provided in one embodiment of the present invention;

[0028] FIG2 is a schematic structural diagram of a silicon-based external cavity laser provided by another embodiment of the present invention;

[0029] FIG3 is a schematic structural diagram of a silicon-based external cavity laser provided by another embodiment of the present invention;

[0030] FIG4 is a schematic structural diagram of a silicon-based external cavity laser provided by another embodiment of the present invention;

[0031] FIG5 is a schematic structural diagram of an auxiliary resonant cavity used in an embodiment of the present invention;

[0032] FIG6 is a schematic structural diagram of a silicon-based external cavity laser provided by another embodiment of the present invention;

[0033] FIG7 is a schematic diagram of the transmittance of the first main resonant cavity, the second main resonant cavity, and the auxiliary resonant cavity used in an embodiment of the present invention. In the figure, the first microring resonant cavity represents the first main resonant cavity, the second microring resonant cavity represents the second main resonant cavity, and the auxiliary microring resonant cavity represents the auxiliary resonant cavity;

[0034] FIG8 is a schematic diagram of the transmittance of the first main resonant cavity, the second main resonant cavity, the third main resonant cavity, and the auxiliary resonant cavity used in an embodiment of the present invention. In the figure, the first microring resonant cavity represents the first main resonant cavity, the second microring resonant cavity represents the second main resonant cavity, the third microring resonant cavity represents the third main resonant cavity, and the auxiliary microring resonant cavity represents the auxiliary resonant cavity.

[0035] FIG9 is a comparison diagram of the reflectivity of an external cavity photon circuit corresponding to a silicon-based external cavity laser utilizing the Vernier effect of two resonant cavities in the prior art and the reflectivity of an external cavity photon circuit corresponding to a silicon-based external cavity laser provided in an embodiment of the present invention, wherein FIG9(a) is a reflectivity diagram of an external cavity photon circuit corresponding to a silicon-based external cavity laser utilizing the Vernier effect of two resonant cavities in the prior art, and FIG9(b) is a reflectivity diagram of an external cavity photon circuit corresponding to a silicon-based external cavity laser including a first main resonant cavity, a second main resonant cavity, and an auxiliary resonant cavity provided in an embodiment of the present invention;

[0036] FIG10 is a comparison diagram of the reflectivity of an external cavity photon circuit corresponding to a silicon-based external cavity laser utilizing the Vernier effect of two resonant cavities in the prior art and the reflectivity of an external cavity photon circuit corresponding to a silicon-based external cavity laser provided in an embodiment of the present invention, wherein FIG10(a) is a reflectivity diagram of an external cavity photon circuit corresponding to a silicon-based external cavity laser utilizing the Vernier effect of two resonant cavities in the prior art, and FIG10(b) is a reflectivity diagram of an external cavity photon circuit corresponding to a silicon-based external cavity laser including three main resonant cavities cascaded in sequence provided in an embodiment of the present invention;

[0037] Figure 11 is a comparison diagram of the external cavity photon circuit reflectivity corresponding to the silicon-based external cavity laser that utilizes the vernier effect of two resonant cavities in the prior art and the external cavity photon circuit reflectivity corresponding to the silicon-based external cavity laser provided in an embodiment of the present invention, wherein (a) in Figure 11 is the external cavity photon circuit reflectivity corresponding to the silicon-based external cavity laser that utilizes the vernier effect of two resonant cavities in the prior art, and (b) in Figure 11 is the external cavity photon circuit reflectivity corresponding to the silicon-based external cavity laser provided in an embodiment of the present invention, which includes a cascade structure of three main resonant cavities cascaded in sequence and an auxiliary resonant cavity.

[0038] Description of reference numerals:

[0039] 100. Silicon-based external cavity chip; 110. Input coupler; 120. Directional coupler; 121. First end; 122. Second end; 123. Third end; 124. Fourth end; 131. First main resonant cavity; 132. Second main resonant cavity; 133. Third main resonant cavity; 140. Sagnac ring; 150. Auxiliary resonant cavity; 160. Output coupler; 170. Waveguide; 180. Connection module; 181. Waveguide; 182. Main resonant cavity; 190. Phase shifter; 200. Light source. DETAILED DESCRIPTION

[0040] The following describes embodiments of the present invention in detail, 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 intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0041] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0042] Furthermore, 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 the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0043] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0045] LiDAR generally includes a transmitting module and a detecting module. The transmitting module includes a laser light source and a transmitting optical system. Depending on its type, the laser light source can use different lasers, such as gas lasers, solid-state lasers, semiconductor lasers, dye lasers, etc. Among them, semiconductor lasers are widely used in today's optical communication systems due to their advantages such as small size, easy integration, simple structure and easy modulation. However, ordinary semiconductor lasers have defects such as poor spectral stability and spectral linewidth, which limit their application in more complex optical communication systems. External cavity semiconductor lasers have the advantages of narrower laser linewidth, wide wavelength tuning range, smaller chirp, and excellent spectral characteristics, and can be well applied to complex optical communication systems, such as dense wavelength division multiplexing fiber communication systems and coherent optical communication systems.

[0046] Specifically, an external cavity semiconductor laser is created by adding optical feedback elements to the outside of the semiconductor laser, forming an external cavity between the back reflective surface of the semiconductor laser and the optical feedback elements. As mentioned above, external cavity semiconductor lasers have two typical structures. Silicon-based photonic chip external cavity narrow linewidth semiconductor lasers offer superior performance, combining the wide tuning and narrow linewidth characteristics of the external cavity structure with the low power consumption and high reliability of the monolithic integrated structure.

[0047] Silicon-based external cavity lasers mainly consist of two parts, including a light source and a silicon-based external cavity chip. The light source is generally efficiently coupled to the silicon-based external cavity chip through a coupler to achieve integrated integration. The silicon-based external cavity chip also includes a resonance module, which includes at least one main resonant cavity. The linewidth of the laser is usually related to the cavity length of the main resonant cavity. The linewidth can be narrowed by increasing the cavity length of the main resonant cavity. However, this operation will increase the number of longitudinal modes of lasing in the main resonant cavity and reduce the gain gap between the longitudinal modes, thereby causing multi-mode lasing problems. Then, it becomes more difficult to obtain stable single-mode lasing and narrow linewidth. In order to effectively avoid the above problems, in silicon-based external cavity lasers, micro-ring resonators (MRRs) with high Q factors are usually selected as frequency selection and mode locking elements because MRRs have a wide free spectral range (FSR). MRRs essentially increase the effective cavity length, thereby improving the photon lifetime, achieving linewidth narrowing and suppressing phase noise and relative intensity noise. In addition, the vernier caliper effect of MRRs can also be used to achieve tuning over a wide wavelength range.

[0048] However, as mentioned above, the current silicon-based external cavity lasers still need to further expand their tunable range while maintaining a narrow linewidth and high side mode suppression ratio. To address the above issues, the embodiments of the present invention provide a resonant module that can utilize the coupling effect of microrings combined with the vernier effect. This resonant module can further expand the tunable range of silicon-based external cavity lasers while maintaining a narrow linewidth and high side mode suppression ratio. This allows the original tuning range of the C-band laser to be expanded to a wider operating range, thereby increasing the application scope and prospects of silicon-based external cavity lasers.

[0049] Please refer to Figures 1 to 4. The resonance module includes multiple main resonant cavities and at least one auxiliary resonant cavity 150. Both the main resonant cavity and the auxiliary resonant cavity 150 are tunable microring resonant cavities. Multiple main resonant cavities are cascaded in sequence through the connection module 180 to form a cascade structure, and a vernier effect can be formed between two adjacent main resonant cavities. When there is a matching auxiliary resonant cavity 150 in the main resonant cavity, the matching main resonant cavity and the auxiliary resonant cavity 150 are coupled so that the free spectrum range of the main resonant cavity is expanded. In this embodiment, the auxiliary resonant cavity 150 can adopt an upload and download structure, as shown in Figure 5. At this time, one end of the auxiliary resonant cavity 150 is connected to the corresponding main resonant cavity, and the other end is coupled to the waveguide 170, as shown in Figures 1 to 4; the auxiliary resonant cavity 150 can also adopt a single waveguide coupling structure. At this time, the auxiliary resonant cavity 150 is directly coupled to the corresponding main resonant cavity, and no waveguide 170 is provided.

[0050] The multiple main resonant cavities are sequentially cascaded through the connection module 180 , which means that the multiple main resonant cavities are arranged in sequence, and any two adjacent main resonant cavities are optically connected through one connection module 180 .

[0051] The presence of a matching auxiliary resonant cavity 150 in the main resonant cavity means that at least one main resonant cavity has an auxiliary resonant cavity 150 that matches itself. The matching mentioned here means that the two can be coupled, and the free spectrum range of the main resonant cavity can be expanded through the mutual coupling between the two. It is understandable that in the resonant module, only one main resonant cavity can be matched with an auxiliary resonant cavity, or multiple main resonant cavities can be respectively provided with corresponding auxiliary resonant cavities, and usually one auxiliary resonant cavity is provided for each main resonant cavity.

[0052] In one embodiment, the cascade structure in the resonance module is a two-stage cascade structure, that is, the cascade structure includes a first main resonant cavity and a second main resonant cavity; one auxiliary resonant cavity is provided and is matched with the first main resonant cavity.

[0053] The first main resonant cavity has a different length from the second main resonant cavity, and the lengths of the first and second main resonant cavities are both integer multiples of the difference. The free spectrum range of the auxiliary resonant cavity is twice the free spectrum range of the first main resonant cavity.

[0054] For ease of understanding, the principle of the resonance module provided in an embodiment of the present invention is described as follows: there are two main resonant cavities, wherein the first-stage main resonant cavity in the cascade structure is the first main resonant cavity 131, the second-stage main resonant cavity in the cascade structure is the second main resonant cavity 132, and there is one auxiliary resonant cavity 150, and the auxiliary resonant cavity 150 is matched with the first main resonant cavity 131.

[0055] 1 , 2 , 7 and 9 , all the resonant cavities involved in this embodiment, including the first main resonant cavity 131 , the second main resonant cavity 132 and the auxiliary resonant cavity 150 , have a free spectral range that satisfies:

[0056] Where λ is the resonant wavelength of the resonant cavity, Δλ is the wavelength interval between adjacent resonant modes of the resonant cavity, ng is the group refractive index of the resonant cavity waveguide, and L is the cavity length of the resonant cavity.

[0057] Among them, there is a difference in cavity length between the first main resonant cavity 131 and the second main resonant cavity 132, and the cavity length of the first main resonant cavity 131 and the cavity length of the second main resonant cavity 132 are both integer multiples of this difference. Therefore, the vernier effect of the microring resonant cavity can be used to expand the free spectral range of the entire external cavity, and the free spectral range and resonant mode of the main resonant cavity can be moved by thermal tuning to achieve the purpose of selecting the laser wavelength output. The FSR of the external cavity after the vernier effect is:

[0058] FSR1 and FSR2 are free spectral ranges of the first main resonant cavity 131 and the second main resonant cavity 132 respectively.

[0059] The auxiliary resonant cavity 150 is coupled to the first main resonant cavity 131. When the cavity length of the auxiliary resonant cavity 150 is half the cavity length of the first main resonant cavity 131, FSR3 = 2FSR1, where FSR3 is the free spectral range of the auxiliary resonant cavity 150. Due to the coupling between the first main resonant cavity 131 and the auxiliary resonant cavity 150, resonant modes with equal wavelengths will couple with each other, resulting in mode splitting, causing the resonant modes that could have been selected for laser output by the vernier effect to be annihilated. Since FSR3 = 2FSR1, every other resonant mode selected for laser output will be annihilated due to the coupling effect. At this time, the FSR of the external cavity due to the coupling effect and the vernier effect is:

[0060] Therefore, the use of the above resonant module can achieve the effect of expanding the tunable range by 2 times. In addition, since the FSR is not only related to the cavity length of the resonant cavity, but also to the refractive index, wavelength, etc., the FSR of the main resonant cavity can also be expanded through other methods.

[0061] When there are more than two main resonant cavities and a plurality of auxiliary resonant cavities 150 , the side mode suppression ratio can be further improved on the basis of expanding the tunable range of the laser.

[0062] In summary, the resonant module provided by the embodiment of the present invention includes multiple main resonant cavities and at least one auxiliary resonant cavity. The multiple main resonant cavities are sequentially cascaded through a connecting module to form a cascade structure, and a vernier effect can be generated between two adjacent main resonant cavities. When a matching auxiliary resonant cavity is present in the main resonant cavity, the free spectrum range of the main resonant cavity can be expanded by coupling the matching main and auxiliary resonant cavities. Combined with the vernier effect of the cascade structure, the tunable range of the laser using the resonant module provided by the embodiment of the present invention is greatly expanded. At the same time, the introduction of the auxiliary resonant cavity 150 in the silicon-based external cavity laser circuit to couple with the main resonant cavity can maintain the narrow linewidth and tunable characteristics of the silicon-based external cavity.

[0063] Referring to Figures 1 to 3 , in some embodiments, the cascade structure is a two-stage cascade structure, including a first main resonant cavity 131 and a second main resonant cavity 132. An auxiliary resonant cavity 150 is provided, matching the first main resonant cavity 131. The cavity lengths of the first and second main resonant cavities differ, and the lengths of the first and second main resonant cavities are both integer multiples of the difference. The free spectral range of the auxiliary resonant cavity is twice the free spectral range of the first main resonant cavity.

[0064] The resonance module adopts the structure provided in this embodiment, which can achieve the effect of expanding the tunable range by 2 times, and the structure of the resonance module is simple and easy to assemble.

[0065] The free spectrum range of the auxiliary resonant cavity is twice that of the first main resonant cavity, which can be achieved through various solutions. In one optional embodiment, the cavity length of the auxiliary resonant cavity is half the cavity length of the first main resonant cavity. The resonant module adopts the structure provided by this embodiment, which can achieve the effect of expanding the tunable range by a factor of two. The resonant module also has a simple structure and is easy to assemble.

[0066] Referring to Figures 4, 8, 10, and 11, in some embodiments, the cascade structure comprises three or more primary resonant cavities sequentially connected in series, with the lengths of each adjacent primary resonant cavity varying. By utilizing the solution provided in this embodiment, the vernier effect of three or more microring resonant cavities can be utilized to expand the free spectral range of the entire external cavity, while simultaneously improving the side mode suppression ratio. Furthermore, the free spectral range and resonant modes of the primary resonant cavities can be shifted through thermal tuning, thereby achieving the goal of selecting the laser wavelength output.

[0067] The resonant module adopts the structure provided in this embodiment, which has a simple structure and is beneficial to improving the side mode suppression ratio compared to the two-stage cascade structure, so that the silicon-based external cavity maintains the characteristics of narrow linewidth, high side mode suppression ratio and wide tunability.

[0068] When the cascade structure is an N-stage (N is an integer greater than 1) cascade structure, the resonant module receives two external input light beams. One input light beam enters the resonant module through the input end of the first-stage main resonant cavity, passes through the N main resonant cavities in sequence, and is coupled out of the resonant module through the output end of the N-stage main resonant cavity. The other input light beam enters the resonant module through the output end of the N-stage main resonant cavity, passes through the N main resonant cavities in sequence, and is coupled out of the resonant module through the input end of the first-stage main resonant cavity.

[0069] The cascade structure in this embodiment can realize bidirectional transmission of light beams. Therefore, when designing the loop, it is only necessary to set up the optical path input / output structure at both ends of the cascade structure to achieve the closure of the entire optical path. There is no need to set up a loop structure outside the cascade structure, making the structure of the entire resonant module simple and easy to design and assemble.

[0070] The connection module 180 can be configured in a variety of ways, which can be flexibly selected according to usage needs.

[0071] 1 and 2 , in some embodiments, the connection module 180 includes a waveguide. The waveguide can be a straight waveguide or a curved waveguide. When the connection module 180 uses a straight waveguide or a curved waveguide, the structure is simple and easy to manufacture.

[0072] As shown in FIG3 , in some other embodiments, connection module 180 includes a waveguide 181 and a main resonant cavity 182. Main resonant cavity 182 is connected to a corresponding main resonant cavity via waveguide 181. The corresponding main resonant cavity is the main resonant cavity adjacent to main resonant cavity 182. Waveguide 181 can be a straight waveguide or a curved waveguide, depending on the application.

[0073] The cavity length of the main resonant cavity 182 may be different from the cavity length of an adjacent main resonant cavity, so that a vernier effect is formed between the main resonant cavity 182 and the adjacent main resonant cavity, thereby further improving the side mode suppression ratio.

[0074] 1 to 4 , an embodiment of the present invention provides a silicon-based external cavity chip 100, comprising an input coupler 110, a directional coupler 120, a resonance module, and an output coupler 160. The resonance module is any of the above embodiments.

[0075] The input coupler 110 is used to couple the optical signal provided by the external light source 200 into the silicon-based external cavity chip 100 .

[0076] The directional coupler 120 receives the optical signal and provides it to the resonant module. The resonant module selects the optical signal and couples the selected optical signal out through the directional coupler 120 and the output coupler 160. The directional coupler 120 in this embodiment can be a 2*2 coupler, a 3*2 coupler, an M*N star coupler, etc., as long as it can achieve the corresponding function.

[0077] The silicon-based external cavity chip 100 provided in an embodiment of the present invention adopts the resonant module provided in any of the above embodiments, expands the vernier effect of the silicon-based external cavity laser 131 using the silicon-based external cavity chip 100 provided in an embodiment of the present invention, greatly expands the tunable range 131 of the laser, and can maintain the narrow linewidth and tunable characteristics of the silicon-based external cavity.

[0078] In some embodiments, the directional coupler 120 has a first end 121, a second end 122, a third end 123, and a fourth end 124. The first end 121, the second end 122, the third end 123, and the fourth end 124 of the directional coupler 120 are respectively connected to the output end of the input coupler 110, the first end of the resonant module, the second end of the resonant module, and the input end of the output coupler 160 via optical paths. Specifically, the directional coupler 120 may be a 2×2 directional coupler.

[0079] The optical signal received by the first end 121 of the directional coupler 120 is split into two input beams in the directional coupler 120. One of the input beams is coupled into the resonance module through the second end 122 of the directional coupler 120 and the first end of the resonance module. After passing through the cascade structure of the resonance modules, it is coupled into the directional coupler 120 through the second end of the resonance module and the third end 123 of the directional coupler 120. It is then provided to the output coupler 160 through the fourth end 124 of the directional coupler 120. The other input beam is coupled into the resonance module through the third end 123 of the directional coupler 120 and the second end of the resonance module. After passing through the cascade structure of the resonance modules, it is coupled into the directional coupler 120 through the first end of the resonance module and the second end 122 of the directional coupler 120. It is then provided to the output coupler 160 through the fourth end 124 of the directional coupler 120.

[0080] For ease of description, the working principle of a silicon-based external cavity laser using the silicon-based external cavity chip 100 provided in an embodiment of the present invention is described by taking FIG1 as an example, where the multiple main resonant cavities in the resonant module include a first main resonant cavity 131 and a second main resonant cavity 132, and an auxiliary resonant cavity 150 is provided, which is coupled with the first main resonant cavity 131.

[0081] The light source emits an optical signal, which is coupled into the silicon-based external cavity chip 100 through the input coupler 110. The optical signal then enters the directional coupler 120 through the first end 121 and is then split into two beams by the directional coupler 120. One beam is coupled into the resonance module through the second end 122, and the other beam is coupled into the resonance module through the third end 123.

[0082] The optical signal entering the resonant module through the second end 122 first propagates within the first main resonant cavity 131. Subsequently, due to the coupling between the first main resonant cavity 131 and the auxiliary resonant cavity 150, resonant modes with equal wavelengths couple with each other, resulting in mode splitting. This annihilates the resonant modes that could have been selected for laser output by the Vernier effect, effectively filtering out the optical signal of the wavelength. The remaining optical signal passes through the connection region between the first main resonant cavity 131 and the connection module 180, is transmitted into the connection module 180, and then is transmitted into the second main resonant cavity 132 through the connection module 180. It is then output through the downstream end of the second main resonant cavity 132 and enters the directional coupler 120 through the third end 123.

[0083] The optical signal entering the resonant module through the third end 123 first propagates within the second main resonant cavity 132 and then enters the first main resonant cavity 131 through the connecting module 180. Subsequently, due to the coupling between the first main resonant cavity 131 and the auxiliary resonant cavity 150, resonant modes with equal wavelengths couple with each other, resulting in mode splitting. This annihilates the resonant mode that could have been selected for laser output by the Vernier effect, i.e., the optical signal of the partial wavelength is filtered out. The remaining optical signal is output through the first main resonant cavity 131 and enters the directional coupler 120 through the second end 122.

[0084] The optical signal then enters the directional coupler 120 and is split into two beams by the directional coupler 120 again. One beam is output through the first end and the input coupler 110 and fed back to the external light source to form a loop, while the other beam is coupled out of the silicon-based external cavity chip 100 through the fourth end 124 and the output coupler 160.

[0085] The silicon-based external cavity chip 100 provided in this embodiment has a simple structure and is easy to assemble.

[0086] Regardless of which of the above methods is used, the above effects can be achieved. In the above embodiments, relying solely on frequency modulation and wavelength adjustment in each main resonant cavity often fails to optimize the output light. Therefore, in some embodiments, as shown in Figures 1 to 4 , the silicon-based external cavity chip 100 further includes a phase shifter 190 connected between the input coupler 110 and the first end of the directional coupler 120. Phase shifter 190 is primarily used for frequency modulation and fine wavelength adjustment to optimize the performance of the output light.

[0087] The above-mentioned phase shifter adopts a thermo-optic phase shifter or an electro-optic phase shifter. When the phase shifter adopts a thermo-optic phase shifter, it has the advantages of low power consumption and low loss. Thermo-optic phase shifters are realized based on the thermo-optic effect of silicon materials. Due to the high thermo-optic coefficient of silicon materials, thermo-optic modulation, which adjusts the optical properties of silicon waveguides by changing the temperature of silicon materials, plays an important role in silicon-based optical devices, especially in the field of low-cost and low-frequency modulation, and is highly attractive. When the phase shifter adopts an electro-optic phase shifter, it has the characteristics of high performance and low power consumption.

[0088] The specific type of the above-mentioned input coupler can be determined according to the specific type of light source. For example, when the light source adopts a semiconductor optical amplifier (SOA), the corresponding input coupler adopts a spot converter; when the light source adopts a laser diode (LD) chip, the input coupler can be etched on a silicon-based external cavity chip; when the light source adopts a vertical cavity surface emitting laser (VCSEL), the corresponding input coupler adopts a grating coupler; the light source and the input coupler are bonded in a flip chip manner.

[0089] In some embodiments, both the input and output couplers utilize spot size converters. In this case, the external light source can be a semiconductor optical amplifier, leveraging existing semiconductor laser technology and facilitating integration with other optical devices. Using spot size converters for both the input and output couplers ensures that the spot size of the components within the silicon-based external cavity chip that interface with the external device is consistent with that of the external device, thereby reducing coupling losses.

[0090] To increase the coupling efficiency of the input coupler and the output coupler, in some embodiments, the input coupler and the output coupler are respectively inverted tapered couplers or forward tapered couplers.

[0091] The power splitting ratio of the directional coupler in the above embodiments can be flexibly selected according to usage requirements. In order to make the line width of the optical signal output through the fourth end narrower and the output power higher, in some embodiments, the power splitting ratio of the directional coupler is 5:5.

[0092] 6 , in another embodiment of the present invention, a silicon-based external cavity chip 100 is provided, comprising an input coupler 110, a resonance module, and a Sagnac ring 140. The resonance module is the resonance module provided in any of the above embodiments.

[0093] The input coupler 110 is used to couple the optical signal provided by the external light source 200 into the silicon-based external cavity chip 100 , and is also used to couple the optical signal fed back by the silicon-based external cavity chip 100 into the external light source 200 .

[0094] A first end of the resonance module is coupled to the input coupler 110 through a waveguide, and a second end of the resonance module is coupled to the Sagnac ring 140 .

[0095] For ease of description, the working principle of a silicon-based external cavity laser using the silicon-based external cavity chip 100 provided in an embodiment of the present invention is described by taking FIG6 as an example, where the multiple main resonant cavities in the resonant module include a first main resonant cavity 131 and a second main resonant cavity 132, and the auxiliary resonant cavity 150 is provided with one, which is coupled with the first main resonant cavity 131.

[0096] The light source emits an optical signal, which is coupled into the silicon-based external cavity chip 100 via the input coupler 110. The optical signal then enters the cascade structure, propagating first within the first main resonant cavity 131. Subsequently, due to the coupling between the first main resonant cavity 131 and the auxiliary resonant cavity 150, resonant modes with equal wavelengths couple with each other, resulting in mode splitting. This annihilates the resonant modes that could have been selected for laser output by the Vernier effect, effectively filtering out the optical signal at certain wavelengths. The remaining optical signal passes through the connection region between the first main resonant cavity 131 and the connection module 180, is transmitted into the connection module 180, and then is transferred to the second main resonant cavity 132 via the connection module 180 before being output from the second main resonant cavity 132.

[0097] The optical signal then enters the Sagnac ring, part of which is output from the silicon-based external cavity chip through the Sagnac ring, and the other part is reflected by the Sagnac ring and coupled out of the silicon-based external cavity chip 100 in the reverse direction through the second main resonant cavity 132, the connection module 180, the first main resonant cavity 131, and the input coupler 110.

[0098] The silicon-based external cavity chip 100 provided in an embodiment of the present invention adopts the resonant module provided in any of the above embodiments, expands the tunable range of the silicon-based external cavity laser using the silicon-based external cavity chip 100 provided in an embodiment of the present invention, and can maintain the narrow linewidth and tunable characteristics of the silicon-based external cavity.

[0099] Regardless of which of the above methods is used, the above effects can be achieved. In the above embodiments, relying solely on frequency modulation and wavelength adjustment in each main resonant cavity often fails to optimize the output light. Therefore, in some embodiments, as shown in FIG6 , the silicon-based external cavity chip 100 further includes a phase shifter 190 connected between the input coupler 110 and the resonant module. Phase shifter 190 is primarily used for frequency modulation and fine-tuning of wavelength to optimize the performance of the output light.

[0100] The above-mentioned phase shifter adopts a thermo-optic phase shifter or an electro-optic phase shifter. When the phase shifter adopts a thermo-optic phase shifter, it has the advantages of low power consumption and low loss. Thermo-optic phase shifters are realized based on the thermo-optic effect of silicon materials. Due to the high thermo-optic coefficient of silicon materials, thermo-optic modulation, which adjusts the optical properties of silicon waveguides by changing the temperature of silicon materials, plays an important role in silicon-based optical devices, especially in the field of low-cost and low-frequency modulation, and is highly attractive. When the phase shifter adopts an electro-optic phase shifter, it has the characteristics of high performance and low power consumption.

[0101] The specific type of the above-mentioned input coupler can be determined according to the specific type of light source. For example, when the light source adopts a semiconductor optical amplifier (SOA), the corresponding input coupler adopts a spot converter; when the light source adopts a laser diode (LD) chip, the input coupler can be etched on a silicon-based external cavity chip; when the light source adopts a vertical cavity surface emitting laser (VCSEL), the corresponding input coupler adopts a grating coupler; the light source and the input coupler are bonded in a flip chip manner.

[0102] In some embodiments, the input coupler utilizes a spot size converter. In this case, the external light source can be a semiconductor optical amplifier, leveraging existing semiconductor laser technology and facilitating integration with other optical components. Using a spot size converter as an input coupler ensures that the spot size of the device in the silicon-based external cavity chip used to connect to the external device is consistent with that of the external device, thereby reducing coupling losses.

[0103] 1 to 6 , another embodiment of the present invention provides a silicon-based external cavity laser, comprising a light source 200 and the silicon-based external cavity chip 100 provided in the above embodiments. The light source 200 is configured to provide an optical signal to the silicon-based external cavity chip 100. The input end of the input coupler 110 is coupled to the output end of the light source 200.

[0104] As mentioned above, the specific type of the input coupler 110 in this embodiment depends on the specific type of the light source 200. In addition to the above components, the silicon-based external cavity laser in this embodiment may also include a housing, an optical fiber, etc., which may be determined according to design requirements.

[0105] The silicon-based external cavity laser provided in the embodiment of the present invention adopts the silicon-based external cavity chip 100 provided in the above embodiments. On the one hand, by introducing the auxiliary resonant cavity 150 to couple with the main resonant cavity, the dual microring resonant cavity coupling effect is combined with the vernier effect to greatly expand the tunable range of the laser. On the other hand, in the silicon-based external cavity laser circuit, the introduction of the auxiliary resonant cavity 150 to couple with the main resonant cavity can maintain the narrow linewidth and tunable characteristics of the silicon-based external cavity.

[0106] In some embodiments, the light source is a semiconductor optical amplifier, and the end of the light source facing away from the silicon-based external cavity chip has a preset reflectivity. The preset reflectivity can be set according to the needs of use. If high reflectivity is required, the preset reflectivity is ≥90%. At this time, the output end of the light source (that is, the end of the light source close to the silicon-based external cavity chip) can be coated with an anti-reflection film to have a low reflectivity, and the reflectivity is ≤0.01%; if light can be emitted from this end, the preset reflectivity can use other values. The gain wavelength of the light source is in the communication band and can be achieved through quantum wells or quantum dot materials of groups III and V. The light source adopts the setting method of this embodiment, which has a simple structure and a small size. It can make full use of existing semiconductor laser technology, has a mature manufacturing process, low cost, long life, low power consumption, and is easy to integrate with other optical devices.

[0107] In another embodiment of the present invention, a laser radar is provided, comprising a laser module, a transmitting module, a detecting module, a detecting module, and a data processing module, wherein the laser module comprises the silicon-based external cavity laser provided in any of the above embodiments.

[0108] The transmitting module in this embodiment can be a commercially available transmitting module. The detecting module in this embodiment can be a commercially available detecting module. The data processing module in this embodiment can be a commercially available data processing module. The laser radar in this embodiment, in addition to the aforementioned laser module, transmitting module, detecting module, and data processing module, may also include at least one of a housing and a scanning device, the specific configuration of which may be determined based on usage requirements.

[0109] The laser radar provided by the embodiment of the present invention includes the silicon-based external cavity laser provided by the above embodiment. On the one hand, it greatly expands the tunable range of the laser; on the other hand, it can maintain the narrow linewidth and tunable characteristics of the silicon-based external cavity, which can effectively improve the scanning angle of the laser radar.

[0110] The foregoing description is merely a preferred embodiment of the present invention and specifically describes the technical principles of the present invention. These descriptions are intended solely to explain the principles of the present invention and should not be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention, as well as other specific embodiments of the present invention that can be devised by those skilled in the art without inventive effort, shall be included within the scope of protection of the present invention.

Claims

1. A resonance module, characterized in that: It comprises a plurality of main resonant cavities and at least one auxiliary resonant cavity, wherein both the main resonant cavity and the auxiliary resonant cavity are tunable micro-ring resonant cavities; The plurality of main resonant cavities are sequentially cascaded through a connection module to form a cascade structure, and a vernier effect can be formed between two adjacent main resonant cavities; When the auxiliary resonant cavity is matched with the main resonant cavity, the matching main resonant cavity and the auxiliary resonant cavity are coupled so that the free spectrum range of the main resonant cavity is expanded.

2. The resonance module according to claim 1, characterized in that: The cascade structure is a two-stage cascade structure, including a first main resonant cavity and a second main resonant cavity; the auxiliary resonant cavity is provided with a matching arrangement with the first main resonant cavity; There is a difference between the cavity length of the first main resonant cavity and the cavity length of the second main resonant cavity, and the cavity length of the first main resonant cavity and the cavity length of the second main resonant cavity are both integer multiples of the difference; The free spectrum range of the auxiliary resonant cavity is twice the free spectrum range of the first main resonant cavity.

3. The resonance module according to claim 2, characterized in that: The cavity length of the auxiliary resonant cavity is 1 / 2 of the cavity length of the first main resonant cavity.

4. The resonance module according to claim 1, characterized in that: The cascade structure is a cascade structure formed by sequentially cascading three or more main resonant cavities, and the difference in cavity lengths between every two adjacent main resonant cavities is different.

5. The resonance module according to any one of claims 1 to 4, characterized in that: When the cascade structure is an N-stage cascade structure, N is an integer greater than 1, and the resonance module receives two input light beams input from the outside; One of the input light beams enters the resonance module through the input end of the first-stage main resonance cavity, and after passing through N of the main resonance cavities in sequence, is coupled out of the resonance module from the download end of the N-stage main resonance cavity; the other input light beam enters the resonance module through the download end of the N-stage main resonance cavity, and after passing through N of the main resonance cavities in sequence, is coupled out of the resonance module from the input end of the first-stage main resonance cavity.

6. The resonance module according to any one of claims 1 to 4, characterized in that: The connection module includes: a waveguide; or a combination structure of a waveguide and one of the main resonant cavities.

7. A silicon-based external cavity chip, characterized in that: It comprises an input coupler, a directional coupler, a resonance module and an output coupler; wherein the resonance module is the resonance module according to any one of claims 1 to 6; Wherein, the input coupler is used to couple the optical signal provided by the external light source into the silicon-based external cavity chip; The directional coupler receives the optical signal and provides it to the resonance module, selects the optical signal through the resonance module, and couples the selected optical signal out through the directional coupler and the output coupler in sequence.

8. The silicon-based external cavity chip according to claim 7, characterized in that: The directional coupler is a 2×2 directional coupler; Wherein, the optical signal received through the first end of the directional coupler is divided into two input light beams in the directional coupler; one of the input light beams is coupled into the resonance module through the second end of the directional coupler and the first end of the resonance module in sequence, and is coupled into the directional coupler through the second end of the resonance module and the third end of the directional coupler after passing through the cascade structure of the resonance module, and is provided to the output coupler by the fourth end of the directional coupler; the other input light beam is coupled into the resonance module through the third end of the directional coupler and the second end of the resonance module in sequence, and is coupled into the directional coupler through the first end of the resonance module and the second end of the directional coupler after passing through the cascade structure of the resonance module, and is provided to the output coupler by the fourth end of the directional coupler.

9. The silicon-based external cavity chip according to claim 7, characterized in that: The silicon-based external cavity chip further includes a phase shifter connected between the input coupler and the first end of the directional coupler.

10. A silicon-based external cavity chip, characterized in that: It comprises an input coupler, a resonance module and a Sagnac ring; the resonance module is the resonance module according to any one of claims 1 to 6; Wherein, the input coupler is used to couple the optical signal provided by the external light source into the silicon-based external cavity chip; The first end of the resonance module is coupled to the input coupler through a waveguide, and the second end of the resonance module is coupled to the Sagnac ring.

11. A silicon-based external cavity laser, characterized in that: It comprises a light source and the silicon-based external cavity chip according to any one of claims 7 to 10, wherein the light source is used to provide an optical signal for the silicon-based external cavity chip.

12. A laser radar, characterized in that: It comprises a laser module, an emission module, a detection module, a detection module and a data processing module, wherein the laser module comprises the silicon-based external cavity laser as claimed in claim 11.

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