High-speed tunable narrow linewidth on-chip external cavity laser and lidar

Abstract

The utility model discloses a kind of narrow line width on-chip external cavity laser of high-speed tuning and laser radar.It contains gain chip and external cavity chip, external cavity chip includes end face coupler, phase shifter, wavelength selector, directional coupler and spiral resonator;Wherein gain chip and the end face coupler one end of external cavity chip are connected with end face optical coupling, end face coupler other end is connected with directional coupler one end in sequence after phase shifter, wavelength selector, directional coupler and spiral resonator are coupled connection, directional coupler other end connects output waveguide, and laser is exported by output waveguide.The utility model can realize the narrow line width laser output of high-speed tuning, to improve the resolution and detection accuracy of laser radar.

Description

Technical Field

[0001] This utility model relates to the field of lidar technology, and mainly to a high-speed tuned narrow-linewidth on-chip external cavity laser and lidar. Background Technology

[0002] As a core component for high-precision 3D sensing, lidar has broad application prospects in remote sensing, surveying, robotics, and autonomous driving. Its performance is highly dependent on the characteristics of the light source, especially the linewidth and wavelength tunability. However, traditional lidar typically uses discrete solid-state lasers or fiber lasers. While these devices offer superior performance, they suffer from large size, high power consumption, and insufficient wavelength tunability, limiting their widespread adoption in miniaturized applications such as automotive systems and drones.

[0003] External cavity lasers (ECLs) integrate functional modules such as gain chips and wavelength selection devices onto a single chip, significantly reducing system size and power consumption to meet the demands of miniaturized and low-power applications. Thanks to their external cavity feedback mechanism, ECLs can further improve laser phase stability and compress laser linewidth. This characteristic is particularly important for frequency modulated continuous wave (FMCW) lidar based on coherent detection, as it can effectively suppress Doppler noise and improve ranging accuracy.

[0004] However, traditional on-chip lasers face numerous challenges in terms of performance and integration. While III-V materials (such as gallium arsenide and indium phosphide) can achieve efficient stimulated emission, they have poor compatibility with CMOS processes. Although IV materials (such as silicon and silicon nitride) have excellent integration capabilities, their intrinsic electro-optic coefficients are low, leading to high power consumption and complex circuit designs. While thin-film lithium niobate (TFLN) platforms have high electro-optic coefficients, they suffer from problems such as DC drift and thermal crosstalk, making it difficult to guarantee reliability during long-term operation and limiting their application in dynamically tunable laser systems. Utility Model Content

[0005] To address the problems existing in the background technology, this utility model proposes a high-speed tuned narrow-linewidth on-chip external cavity laser and lidar, which solves the technical problem of the multi-dimensional contradiction between miniaturization, dynamic tuning, low power consumption and high performance of traditional lidar light sources.

[0006] This invention enables high-speed tuning of narrow-linewidth laser output, thereby improving the resolution and detection accuracy of lidar.

[0007] The technical solution of this utility model is:

[0008] This utility model includes a gain chip and an external cavity chip. The external cavity chip includes an end-face coupler, a phase shifter, a wavelength selector, a directional coupler, and a spiral resonator.

[0009] The gain chip and the external cavity chip are optically coupled at one end of the end face coupler. The other end of the end face coupler is connected to one end of the directional coupler after passing through a phase shifter and a wavelength selector. The directional coupler is coupled to a spiral resonator. The other end of the directional coupler is connected to the output waveguide, through which the laser is output.

[0010] The laser is input into the external cavity chip and passes through the phase shift region. The phase shift region adjusts the refractive index of the waveguide through the electro-optic effect of materials including but not limited to lead zirconate titanate, thereby adjusting the phase of the fabricated optical resonator. After passing through the phase shift region, the laser enters the wavelength selector.

[0011] The gain chip generates a broadband signal light with multiple wavelengths. The broadband signal light is incident through the end-face coupler, then the phase is adjusted by the phase shifter, and then wavelength selective transmission and reflection occur through the wavelength selector. Part of the reflected signal light returns to the phase shifter, and then returns to the gain chip through the end-face coupler. After being reflected in the gain chip, it is re-injected into the end-face coupler, and then continuously propagates back and forth between the gain chip and the wavelength selector.

[0012] Another portion of the transmitted signal light is incident into the directional coupler, where it is coupled and then directly emitted:

[0013] The directional coupler couples a portion of the signal light to the spiral resonator, which further compresses the linewidth. The compressed signal light is then coupled back between the wavelength selector and the directional coupler and back to the gain chip, thus propagating back and forth between the gain chip and the wavelength selector.

[0014] The directional coupler directs another portion of the signal light directly out from the output end of the external cavity chip via the output waveguide, outputting the signal light at the resonant wavelength.

[0015] Preferably, the gain chip employs a reflective semiconductor optical amplifier (RSOA), with a high reflectivity at one end and a low reflectivity at the other, to achieve efficient unidirectional transmission of optical signals. The low-reflectivity end of the RSOA serves as the output port, connected to an end-face coupler on the external cavity chip, for transmitting broadband signal light to the external cavity chip. Furthermore, both the output port of the RSOA and the end-face coupler utilize tilted waveguide structures to effectively reduce system reflections and prevent laser linewidth broadening.

[0016] The external cavity chip is based on the TFPZT platform, and all devices on it use TFPZT waveguides. This waveguide has low temperature sensitivity and negligible DC drift, thereby significantly improving the performance stability and reliability of the laser under long-term operating conditions.

[0017] The end-face coupler adopts a tapered structure.

[0018] The phase shifter is one or more of a thermo-optical phase shifter, an electro-optical phase shifter, or a piezoelectric phase shifter, used to adjust the phase of the signal light;

[0019] The wavelength selector employs a waveguide Bragg grating or micro-ring resonator structure, and its resonant peak overlaps with the broadband light output by the gain chip.

[0020] The wavelength selector is used to select a specific wavelength to be reflected back to the gain chip and forms an optical resonant cavity with the reflecting end of the gain chip. A self-injection locking mechanism compresses the broadband light output from the gain chip. Furthermore, depending on the requirements, thermally tunable, electrically tunable, or other tuning structures can be selected to change the desired wavelength, thereby achieving superior wavelength tunability.

[0021] The directional coupler is used to transmit a portion of the signal light at the resonant wavelength to the spiral resonator. The transmitted signal light power is equal to the internal loss of the spiral resonator, so that the spiral resonator operates in a critical coupling state to maximize the linewidth compression effect.

[0022] The spiral resonator is composed of a width-gradient Euler S-curve waveguide and a double Archimedean spiral waveguide. Its intrinsic Q value is higher than that of the wavelength selector, and its resonance peak overlaps with that of the wavelength selector, so as to further compress the laser linewidth.

[0023] The system comprises several components: an end-face coupler, which receives the broadband light output from the gain chip and employs a tilted TFPZT waveguide structure to reduce stray light reflected back to the gain chip and prevent laser linewidth broadening; a phase shifter, located after the end-face coupler, adjusts the phase of the laser in the external cavity chip by changing the refractive index of the TFPZT, effectively altering the length of the optical resonant cavity; a wavelength selector selects a specific wavelength of laser light to be reflected back to the gain chip, initially compressing the laser linewidth through a self-injection locking mechanism; and a directional coupler, which couples a portion of the signal light to the spiral resonator, bringing it to a critical coupling state where its Q-value reaches its maximum. The spiral resonator essentially extends the length of the optical resonant cavity, further amplifying the laser power and compressing the laser linewidth. The signal light emitted from the spiral resonator and the signal light emitted from the directional coupler are superimposed to form the final narrow-linewidth laser output.

[0024] The output terminal of the external cavity chip outputs laser light using end-face coupling or fiber coupling.

[0025] The tuning structure of the wavelength selector and the spiral resonator adopts one or more combinations of thermo-optical tuning, electro-optical tuning, or piezoelectric tuning to achieve wavelength tuning function, so as to flexibly adjust the reflected wavelength of the device resonance peak, thereby giving the external cavity laser superior wavelength tuning capability.

[0026] The directional coupler enables the spiral resonator to operate in critical coupling mode. In critical coupling mode, the loaded Q value of the spiral resonator reaches its maximum, thereby achieving optimal linewidth compression of the signal light.

[0027] The gain chip, end coupler, phase shifter, and wavelength selector together form the laser optical resonant cavity for signal light propagation.

[0028] Each part within the external cavity chip adopts an optical waveguide structure, and the core layer within the optical waveguide structure is made of lead zirconate titanate material. By changing the refractive index of lead zirconate titanate material through its electro-optic properties, the phase of the laser optical resonator is thus changed.

[0029] The innovation of this invention lies in designing the external cavity laser as a three-cavity mirror structure consisting of an RSOA, a wavelength selector, and a spiral resonator. This allows for the utilization of the single resonant peak characteristic of the wavelength selector to achieve high longitudinal mode rejection ratio laser output. Furthermore, the waveguide core layer uses a specially prepared, pre-calibrable lead zirconate titanate material, which ensures precise matching between the resonant peak of the wavelength selector and the resonant peak of the spiral resonator, enabling high-speed tuning and extremely narrow linewidth laser output.

[0030] Compared to other external cavity laser configurations, this structure has a strong linewidth compression effect. With a laser output center wavelength of 1550nm, the laser linewidth measured using the delayed self-heterodyne method is approximately 9Hz.

[0031] The lead zirconate titanate material used has a strong electro-optic effect compared to conventional core materials, and the highest modulation efficiency measured so far is 100 pm / V.

[0032] The optical waveguide structure includes a substrate and a TFPZT flat plate, a TFPZT trace waveguide, and a waveguide cladding layer stacked on the substrate from bottom to top. The substrate is mainly composed of an upper substrate layer (105) and a lower substrate layer stacked on top of each other. The waveguide cladding layer covers the TFPZT trace waveguide. The TFPZT trace waveguide is made of lead zirconate titanate material.

[0033] Metal electrodes are further disposed on the TFPZT flat plates on both sides of the TFPZT trace waveguide, and the waveguide cladding covers the TFPZT trace waveguide and the metal electrodes.

[0034] In external cavity chips, all phase shifters, wavelength selectors, directional couplers, and spiral resonators except for the end-face coupler have metal electrodes, while the end-face coupler does not have metal electrodes.

[0035] The phase shifter is provided with a metal electrode for electro-optic tuning;

[0036] The wavelength selector employs a waveguide Bragg grating.

[0037] The directional coupler uses an adiabatic waveguide with gradually changing curvature, and the gradual change direction of the adiabatic waveguide is arranged from large to small along the positive propagation direction of the signal light.

[0038] The spiral resonator adopts a double-helix resonant cavity based on Euler curves. Specifically, the double-helix resonant cavity based on Euler curves is composed of two concentrically interlaced Euler curve waveguides. The inner ends of the two spiral Euler curve waveguides are connected by S-shaped waveguides, and the outer ends of the two spiral Euler curve waveguides are connected by bent waveguides.

[0039] The high-speed tuned narrow-linewidth on-chip external cavity laser of this invention is used to emit wavelength-tunable narrow-linewidth lasers to improve the resolution and detection accuracy of lidar.

[0040] The narrow linewidth mentioned in this invention refers to the frequency width of the laser's emission spectrum at half maximum width (FWHM) being less than 10 Hz.

[0041] This utility model has the following advantages:

[0042] First, it can effectively compress the linewidth of the laser and improve the wavelength tuning capability of the light source, thereby improving the resolution and detection accuracy of the lidar.

[0043] Secondly, this invention is based on TFPZT and adopts a wafer-level sol-gel process compatible with CMOS, which supports low-cost, high-density integration and provides feasibility for large-scale applications. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of this utility model, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this utility model.

[0045] Figure 1 This is a schematic diagram of a narrow-linewidth tunable on-chip external cavity laser structure provided by an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the specific structure of a narrow-linewidth tunable on-chip external cavity laser provided in this embodiment of the present invention;

[0047] Figure 3 yes Figure 2 A cross-sectional schematic diagram of the TFPZT waveguide and the metal tuning electrode in the diagram.

[0048] Figure 4 yes Figure 2 A schematic diagram of the specific structure of the double-helix resonant cavity based on Euler curves;

[0049] Figure 5yes Figure 2 The diagram shows the transmission spectrum of the broadband signal light emitted from the gain chip, the reflection spectrum of the waveguide Bragg grating, the reflection spectrum of the double-helix resonant cavity, and the transmission spectrum of the laser emitted from the external cavity laser.

[0050] In the figure: gain chip (C1) and external cavity chip (C2); end face coupler (C21), phase shifter (C22), wavelength selector (C23), directional coupler (C24), helical resonator (C25); metal electrode (C26), waveguide Bragg grating (C27), thermally adiabatic waveguide with gradually varying curvature (C28), and double helical resonator based on Euler curve (C29). Detailed Implementation

[0051] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0052] like Figure 1 As shown, the narrow linewidth on-chip external cavity laser includes a gain chip C1 and an external cavity chip C2. The gain chip C1 is a single-sided strong reflective SOA with a tilted exit angle. The external cavity chip C2 includes an end-face coupler C21, a phase shifter C22, a wavelength selector C23, a directional coupler C24, and a spiral resonator C25.

[0053] The gain chip C1 and the external cavity chip C2 are optically coupled at one end of the end face coupler C21. The other end of the end face coupler C21 is connected to one end of the directional coupler C24 after passing through the phase shifter C22 and the wavelength selector C23. The middle part of the directional coupler C24 is coupled to the spiral resonator C25 through the evanescent field. The other end of the directional coupler C24 is connected to the output waveguide, and the laser is output from the output end of the external cavity chip C2 through the output waveguide.

[0054] A broadband signal light carrying multiple wavelengths is generated in the gain chip C1. The broadband signal light is incident on the external cavity chip C2 through the end coupler C21, and then the phase is adjusted by the phase shifter C22. Then, wavelength selective transmission and reflection occur through the wavelength selector C23. Part of the reflected signal light returns to the phase shifter C22, and then returns to the gain chip C1 through the end coupler C21. The linewidth is initially compressed through the self-injection locking mechanism. After being reflected in the gain chip C1, it is re-injected into the end coupler C21, and then continuously propagates back and forth between the gain chip C1 and the wavelength selector C23.

[0055] Another portion of the transmitted signal light is incident on the directional coupler C24, where it is coupled and directly emitted:

[0056] The directional coupler C24 couples a portion of the signal light at the resonant wavelength to the spiral resonator C25. The high Q value of the spiral resonator C25 further compresses the linewidth. The signal light after the linewidth is compressed by the spiral resonator C25 is coupled back between the wavelength selector C23 and the directional coupler C24 and then back to the gain chip C1, thus propagating back and forth between the gain chip C1 and the wavelength selector C23.

[0057] The directional coupler C24 directly outputs another portion of the signal light at the resonant wavelength from the output terminal of the external cavity chip C2 through the output waveguide, thus outputting the signal light at the resonant wavelength.

[0058] The input port of the directional coupler receives the signal light from the wavelength selector and transmits part of the signal light to the spiral resonator; at the output port, the remaining signal light is output directly from the output end.

[0059] The splitting ratio in the directional coupler C24 must satisfy the condition that the optical power coupled into the spiral resonator is equal to the internal loss of the spiral resonator.

[0060] The end-face coupler C21 adopts a tapered structure, specifically a positive tapered or inverted tapered structure, to maximize the mode matching degree between the gain chip and the external cavity chip, and to optimize the optical coupling efficiency between the gain chip C1 and the external cavity chip C2.

[0061] The phase shifter C22 employs one or more of the following: thermo-optical phase shifter, electro-optical phase shifter, or piezoelectric phase shifter, to adjust the phase of the signal light; precise adjustment of the light wave phase is achieved by changing the refractive index of the TFPZT.

[0062] The wavelength selector C23 uses a waveguide Bragg grating C27 or a micro-ring resonator structure. Its resonant peak intersects with the broadband light output by the gain chip C1 to achieve the selection of a specific wavelength.

[0063] The directional coupler C24 is used to transmit the signal light portion at the resonant wavelength to the spiral resonator C25 and to make the spiral resonator C25 operate in the critical coupling state to maximize the linewidth compression effect.

[0064] The spiral resonator C25 is composed of a gradually widened Euler S-curve waveguide and a double Archimedean spiral waveguide. Its intrinsic Q value is higher than that of the wavelength selector C23, and its resonance peak overlaps with that of the wavelength selector C23, in order to further compress the laser linewidth.

[0065] The intrinsic Q-value of the spiral resonator is greater than that of the wavelength selector, thus further compressing the laser linewidth. The reflection spectrum of the spiral resonator can be adjusted through a tuning structure, causing its resonance peak to intersect with that of the wavelength selector.

[0066] Preferably, the directional coupler C24 enables the spiral resonator C25 to operate in the critical coupling mode. In the critical coupling mode, the loaded Q value of the spiral resonator C25 reaches its maximum, thereby achieving the optimal linewidth compression effect of the signal light.

[0067] The relationship between the Q value and the linewidth of the laser wavelength is as follows:

[0068]

[0069] Among them, Q factor Let λ be the Q value. res The center wavelength is λ, and FWHM is the linewidth of the laser.

[0070] As can be seen, the Q value is inversely proportional to the linewidth of the laser; the higher the Q value, the smaller the linewidth of the laser, thus achieving the ultimate compression of the linewidth.

[0071] The laser optical resonator, consisting of gain chip C1, end coupler C21, phase shifter C22, and wavelength selector C23, forms the laser optical resonator for signal light propagation.

[0072] Each part of the external cavity chip C2 adopts an optical waveguide structure. The core layer of the optical waveguide structure is made of lead zirconate titanate material. By changing the refractive index of lead zirconate titanate material through its electro-optic properties, the phase of the laser optical resonator can be changed.

[0073] Specifically, lead zirconate titanate material is prepared using the following method:

[0074] S1. The PZT precursor solution is uniformly spread on the substrate surface by spin coating and pre-baked at 250°C to remove organic components.

[0075] S2. By using the rapid thermal annealing (RTA) process to anneal the film to 450°C in an oxygen environment and holding it at that temperature for a period of time, a perovskite phase structure with high crystallinity can be achieved.

[0076] S3. Repeat the spin coating and annealing process of the above steps S1 and S2 multiple times to achieve the target film thickness, thereby preparing a lead zirconate titanate thin film.

[0077] The resulting lead zirconate titanate (PZT) thin film exhibits low surface roughness and excellent thickness uniformity, which is beneficial for enhancing the electro-optic effect. This novel PZT thin film fabrication process possesses large-scale on-chip integration capabilities, which is conducive to integration with silicon photonics platforms or other photonic integration platforms, and has broad application prospects.

[0078] The prepared lead zirconate titanate material exhibits a strong electro-optic effect, achieving a modulation efficiency of up to approximately 100 pm / V, which provides favorable conditions for narrow linewidths in external cavity lasers.

[0079] Lead zirconate titanate exhibits a strong electro-optic effect, which is also reflected in the resonant cavities made from it. After polarization, the resonant peak changes significantly with voltage, resulting in high modulation efficiency and enabling high-speed, wide-range resonant tuning.

[0080] The solutes in the PZT precursor solution include lead acetate trihydrate (Pb(CH3COO)2·3H2O), zirconium isopropoxide (Zr(OCH(CH3)2)4), and tetrabutyl titanate (Ti(OCH2CH2CH2CH3)4), with a total metal ion concentration of 0.3 mol / L. The solvents are ethylene glycol methyl ether and acetylacetone.

[0081] The substrate is specifically silicon dioxide (upper substrate layer 105) and silicon (lower substrate layer 106).

[0082] The optical waveguide structure includes a substrate and, from bottom to top, a TFPZT flat plate 104, a TFPZT trace waveguide 103, and a waveguide cladding 101 stacked on the substrate. The substrate is mainly composed of an upper substrate layer 105 and a lower substrate layer 106 stacked on top of each other. The waveguide cladding 101 covers the TFPZT trace waveguide 103 and the metal electrode 102. The TFPZT trace waveguide 103 is made of lead zirconate titanate material.

[0083] Metal electrodes 102 are further disposed on the TFPZT flat plates 104 on both sides of the TFPZT trace waveguide 103, and the waveguide cladding 101 covers the TFPZT trace waveguide 103 and the metal electrodes 102.

[0084] Preferably, based on the characteristics of TFPZT, by selecting appropriate ferroelectric polarization and bias voltage applied to the metal electrode 102, the effective electro-optic coefficient can be significantly enhanced. This not only improves the tuning speed of the electro-optic tuning structure in the wavelength selector and spiral resonator, as well as the phase modulation speed of the electro-optic phase shifter, but also reduces the driving voltage while achieving the same modulation depth, thereby realizing the laser's superior wavelength tuning capability and efficient energy consumption control performance.

[0085] Specifically, this means that a metal electrode C26 for electro-optic tuning is provided on top of the phase shifter C22;

[0086] Wavelength selector C23 uses waveguide Bragg grating C27;

[0087] The directional coupler C24 uses a thermally insulated waveguide C28 with gradually changing curvature. The thermally insulated waveguide C28 with gradually changing curvature is arranged from large to small along the positive transmission direction of the signal light.

[0088] The spiral resonator C25 adopts a double-helix resonator C29 based on Euler curves. Specifically, the double-helix resonator C29 is composed of two concentrically interlaced Euler curve waveguides. The inner ends of the two spiral Euler curve waveguides are connected by S-shaped waveguides to form a shape similar to an octagon. The outer ends of the two spiral Euler curve waveguides are connected by bent waveguides.

[0089] The signal light transmitted to the phase shifter C22 is subjected to voltage through the metal electrode C26 and the phase of the signal light is modulated by electro-optic tuning, which is used to coarsely adjust the resonant wavelength and change the output power of the laser.

[0090] The signal light transmitted to the waveguide Bragg grating C27 undergoes wavelength-selective transmission and reflection. The waveguide Bragg grating C27 returns most of the non-output wavelength signal light to the phase shifter C22, and directs a small portion of the signal light close to the output wavelength into the adiabatic waveguide C28.

[0091] The light transmitted to the adiabatic waveguide C28 undergoes direct emission and coupling. The adiabatic waveguide C28 couples a portion of the light that meets the resonant wavelength condition into the double-helix resonant cavity C29. The power of the coupled signal light is equal to the internal loss of the double-helix resonant cavity C29. At this time, the double-helix resonant cavity C29 operates in a critical coupling state, and the energy is completely stored in the resonant cavity, forming a high-Q resonance. The adiabatic waveguide C28 then directly emits the remaining portion of the signal light that meets the resonant wavelength condition from the output end.

[0092] Due to the backscattering characteristics of the waveguide, the double-helix resonator C29 couples a very small portion (approximately 1% in actual measurement) of the signal light input to the helical resonator back between the wavelength selector C23 and the directional coupler C24 and back to the gain chip C1. Through the self-injection locking mechanism, the output linewidth of the laser is further compressed.

[0093] The signal light propagation process from the adiabatic waveguide C28 to the double-helix resonant cavity C29 and the signal light propagation process from the double-helix resonant cavity C29 to the adiabatic waveguide C28 and the waveguide Bragg grating C27 occur simultaneously, and both occur on the waveguide segment where the adiabatic waveguide C28 is located.

[0094] The following describes the specific structure of a high-speed tuned narrow-linewidth on-chip external cavity laser, such as... Figure 2 As shown, the phase shifter is composed of an electro-optically tuned metal electrode C26, the wavelength selector is a waveguide Bragg grating C27, the directional coupler is an adiabatic waveguide with gradually varying curvature C28, and the spiral resonator is a double-helix resonant cavity C29 based on Euler curves.

[0095] like Figure 3The diagram shows an electro-optically tuned metal electrode structure suitable for phase-shift regions, waveguide Bragg gratings, and double-helix resonators, as well as a TFPZT trace waveguide structure. It includes: a waveguide upper cladding 101, metal electrodes 102, a TFPZT trace waveguide 103, a TFPZT planar plate 104, an upper substrate layer 105, and a lower substrate layer 106. The metal electrodes are deposited on the TFPZT planar plate and located on both sides of the TFPZT trace waveguide or device. The trace waveguide has a trapezoidal ridge waveguide cross-section with a certain tilt angle to optimize signal light transmission loss. In a typical TFPZT platform, the waveguide upper cladding and upper substrate layer are made of silicon dioxide, the lower substrate layer is made of silicon, and the metal electrodes can be made of gold.

[0096] like Figure 4 The diagram shown is a schematic of the specific structure of a spiral resonator. Figure 4 (a) illustrates the overall structure of the spiral resonator, including a width-gradient Euler S-curve waveguide S1 and a double Archimedean spiral waveguide S2. The two Archimedean spiral waveguides are connected at their starting points via an Euler S-curve waveguide and at their ending points via a 180° circular waveguide, thus forming a closed spiral micro-ring resonator. The specific expression for the Euler S-curve is:

[0097]

[0098] Where θ is the angle of the corresponding arc, L is the length of the corresponding arc, R is the radius of curvature of the corresponding arc, and C represents the rate at which the arc angle changes with the arc length, specifically set as a constant. t R is the total length of the Euler curve. max With R min These are the maximum and minimum values ​​of the radius of curvature, respectively.

[0099] Figure 4 (b) illustrates the specific structure of the Euler S-curve waveguide, which consists of two 180° arc-shaped waveguides with simultaneously varying widths and curvatures. Taking one of the 180° arc-shaped waveguides as an example, the waveguide width is maximum at the input port, then changes linearly, reaching a minimum at the output port. Simultaneously, the waveguide radius of curvature varies according to the aforementioned Euler curve, with the radius of curvature being maximum at the input port, reaching a minimum at the quarter-arc, then gradually increasing, returning to a maximum at the output port. As the waveguide width gradually narrows, its minimum bending radius also decreases. By varying the radius of curvature of the Euler curve, the generation of higher-order modes during signal light transmission is effectively avoided, and the footprint of the double-helix resonant cavity is significantly reduced, thereby promoting high-density integration on the TFPZT platform.

[0100] The following is combined Figure 5 This invention provides a detailed explanation of the linewidth compression process of the external cavity laser provided in this embodiment.

[0101] like Figure 5 (a) shows the transmission spectrum of the broadband signal light emitted by the gain chip, which is transmitted to the external cavity chip through the end coupler.

[0102] like Figure 5 (b) shows the reflection spectrum of the waveguide Bragg grating. The desired wavelength is selected by adjusting the voltage applied across the two ends of the waveguide Bragg grating and reflected back to the gain chip. The laser linewidth is initially compressed by using the self-injection locking mechanism.

[0103] like Figure 5 (c) shows the reflection spectrum of the double-helix resonator. By adjusting the resonant peaks of the double-helix resonator through a tuning structure, one and only one resonant peak is aligned with the resonant peak of the waveguide Bragg grating, while the remaining resonant peaks fall outside the reflection peak of the waveguide Bragg grating. This further compresses the laser linewidth while maintaining a high side-mode suppression ratio. Furthermore, the laser phase is adjusted using an electro-optic phase shifter to achieve the highest power output in the selected laser mode.

[0104] like Figure 5 (d) shows the final laser transmission spectrum emitted by the external cavity laser, demonstrating the linewidth compression effect of the external cavity chip.

[0105] Accordingly, this utility model embodiment also provides a lidar, including: an on-chip external cavity laser for emitting a high-speed tuned narrow linewidth laser.

[0106] The lidar provided in this embodiment of the present invention uses an on-chip external cavity laser as described in any of the above embodiments, and has the following advantages: by significantly compressing the laser linewidth, the resolution and detection accuracy of the lidar are significantly improved; it supports high-speed wavelength tuning and broadband wavelength tuning capabilities, expanding the scanning range of the lidar; and it has low temperature sensitivity and a high side-mode rejection ratio, improving the reliability and stability of the lidar.

[0107] The above embodiments are used to explain and illustrate the present utility model, and are not intended to limit the present utility model. Any modifications and changes made to the present utility model within the spirit and scope of the claims shall fall within the protection scope of the present utility model.

Claims

1. A high-speed tuned narrow-linewidth on-chip external cavity laser, characterized in that, It includes a gain chip (C1) and an external cavity chip (C2). The external cavity chip (C2) includes an end face coupler (C21), a phase shifter (C22), a wavelength selector (C23), a directional coupler (C24), and a spiral resonator (C25). The gain chip (C1) and the external cavity chip (C2) are optically coupled at one end of the end face coupler (C21). The other end of the end face coupler (C21) is connected to one end of the directional coupler (C24) after passing through the phase shifter (C22) and the wavelength selector (C23). The directional coupler (C24) is coupled to the spiral resonator (C25). The other end of the directional coupler (C24) is connected to the output waveguide, through which the laser is output.

2. The high-speed tuned narrow-linewidth on-chip external cavity laser according to claim 1, characterized in that: The gain chip (C1) generates a broadband signal light with multiple wavelengths. The broadband signal light is incident through the end coupler (C21), then the phase is adjusted by the phase shifter (C22), and then wavelength selective transmission and reflection occur through the wavelength selector (C23). A portion of the reflected signal light returns to the phase shifter (C22), and then returns to the gain chip (C1) through the end coupler (C21). After being reflected in the gain chip (C1), it is re-injected into the end coupler (C21), and then continuously propagates back and forth between the gain chip (C1) and the wavelength selector (C23). Another portion of the transmitted signal light is incident on the directional coupler (C24) and coupled and directly emitted: the directional coupler (C24) couples a portion of the signal light to the spiral resonator (C25), which further compresses the linewidth. The signal light after linewidth compression by the spiral resonator (C25) is coupled back between the wavelength selector (C23) and the directional coupler (C24) and back to the gain chip (C1), and then propagates back and forth between the gain chip (C1) and the wavelength selector (C23); the directional coupler (C24) directly emits another portion of the signal light from the output end of the external cavity chip (C2) through the output waveguide, and outputs the signal light at the resonant wavelength.

3. The high-speed tuned narrow-linewidth on-chip external cavity laser according to claim 1, characterized in that, The phase shifter (C22) is one or more of a thermo-optical phase shifter, an electro-optical phase shifter, or a piezoelectric phase shifter, used to adjust the phase of the signal light; the wavelength selector (C23) is a waveguide Bragg grating (C27) or a micro-ring resonant cavity structure, whose resonant peak intersects with the broadband light output by the gain chip (C1).

4. The high-speed tuned narrow-linewidth on-chip external cavity laser according to claim 1, characterized in that, The directional coupler (C24) is used to transmit a portion of the signal light at the resonant wavelength to the spiral resonator (C25). The transmitted signal light power is equal to the internal loss of the spiral resonator, so that the spiral resonator (C25) operates in a critical coupling state to maximize the linewidth compression effect. The spiral resonator (C25) is composed of a width-gradient Euler S-curve waveguide and a double Archimedean spiral waveguide. Its intrinsic Q value is higher than that of the wavelength selector (C23), and its resonance peak overlaps with the resonance peak of the wavelength selector (C23) to further compress the laser linewidth.

5. The high-speed tuned narrow-linewidth on-chip external cavity laser according to claim 1, characterized in that, The directional coupler (C24) enables the spiral resonator (C25) to operate in critical coupling mode. In critical coupling mode, the loaded Q value of the spiral resonator (C25) reaches its maximum, thereby achieving optimal linewidth compression of the signal light.

6. The high-speed tuned narrow-linewidth on-chip external cavity laser according to claim 1, characterized in that, The gain chip (C1), end coupler (C21), phase shifter (C22), and wavelength selector (C23) together form a laser optical resonant cavity for signal light propagation.

7. The high-speed tuned narrow-linewidth on-chip external cavity laser according to claim 6, characterized in that, Each part of the external cavity chip (C2) adopts an optical waveguide structure. The core layer of the optical waveguide structure is made of lead zirconate titanate material. By changing the refractive index of lead zirconate titanate material through its electro-optic properties, the phase of the laser optical resonator is changed.

8. The high-speed tuned narrow-linewidth on-chip external cavity laser according to claim 7, characterized in that, The optical waveguide structure includes a substrate and a TFPZT flat plate (104), a TFPZT trace waveguide (103), and a waveguide cladding (101) stacked on the substrate from bottom to top. The substrate is mainly composed of an upper substrate layer (105) and a lower substrate layer (106) stacked on top of each other. The waveguide cladding (101) covers the TFPZT trace waveguide (103). The TFPZT trace waveguide (103) is made of lead zirconate titanate material. Metal electrodes (102) are further disposed on the TFPZT flat plates (104) on both sides of the TFPZT trace waveguide (103), and the waveguide cladding (101) covers the TFPZT trace waveguide (103) and the metal electrodes (102).

9. The high-speed tuned narrow-linewidth on-chip external cavity laser according to claim 1, characterized in that: The phase shifter (C22) is provided with a metal electrode (C26) for electro-optic tuning. The wavelength selector (C23) employs a waveguide Bragg grating (C27). The directional coupler (C24) adopts a thermally aerated waveguide (C28) with gradually changing curvature. The thermally aerated waveguide (C28) with gradually changing curvature is arranged from large to small along the positive propagation direction of the signal light. The spiral resonator (C25) adopts a double-helix resonant cavity (C29) based on Euler curves. Specifically, the double-helix resonant cavity (C29) based on Euler curves is composed of two spiral Euler curve waveguides arranged in a concentric staggered spiral configuration. The inner ends of the two spiral Euler curve waveguides are connected by S-shaped waveguides, and the outer ends of the two spiral Euler curve waveguides are connected by bent waveguides.

10. A lidar, comprising: The invention includes a high-speed tuned narrow-linewidth on-chip external cavity laser according to any one of claims 1-9, for emitting wavelength-tunable narrow-linewidth lasers to improve the resolution and detection accuracy of lidar.

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