A high-power soliton frequency comb chip and its pulse generation system and method

Abstract

The present invention relates to a high-power soliton frequency comb chip and its pulse generation system and method. The soliton frequency comb chip includes a substrate, a micro-ring resonant cavity and a straight waveguide; the straight waveguide includes a multi-mode waveguide, a multi-mode single-mode transition cone waveguide, a single-mode waveguide and a single-mode slot waveguide from one end to the other end, the wide end of the multi-mode single-mode transition cone is connected to the multi-mode waveguide, the narrow end of the multi-mode single-mode transition cone is connected to one end of the single-mode waveguide, and the other end of the single-mode waveguide is coupled to the single-mode lot waveguide through a linear strip-to-slot mode converter; the micro-ring resonant cavity is located on one side of the multi-mode waveguide and is coupled to the multi-mode waveguide. The present invention combines the idea of ​​laser coherent ranging, uses the frequency comb micro-cavity structure to be integrated on the micro-nano waveguide, and at the same time, the generated soliton frequency comb is optically amplified on the chip to achieve signal gain amplification, thereby realizing a new integrated design of the optical system of the ranging transmitter end, and effectively improving the measurement efficiency.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technology, and more specifically, to a high-power soliton frequency comb chip and a pulse generation system and method thereof. Background Art

[0002] Existing automotive-grade LiDARs are divided into mechanical rotation type, MEMS type, Flash type, and phased type according to the scanning method. At present, mechanical rotation type and MEMS type LiDARs are mature enough for market application in assisting intelligent driving. Mechanical LiDAR itself is the simplest to use, with an electronically controlled rotation machine for 360° scanning. Its optical discrete devices at the transmitting end are complex, inefficient, and have high power consumption, which limits its practicality and response sensitivity in close to real and complex road conditions. MEMS type and others have built-in micro-nano scanning mirrors. Other non-mechanical LiDARs also have problems such as complex optical device etching process, high cost, and low power output efficiency at the transmitting end. At the same time, they are accompanied by problems such as low lifespan and the need for many auxiliary devices, and have not been able to serve the autonomous driving car market well.

[0003] At present, LiDAR distance measurement technology is still in the introduction stage, and different speed and distance measurement technologies are being continuously developed. What cannot be avoided is the need for a good-performance laser signal transmitter in hardware, which can achieve multi-channel, high efficiency, long scanning distance, and high sensitivity performance indicators. However, most of the current transmitters are composed of complex discrete optical devices, which require lenses, polarizers, analyzers, etc. to form an optical system. There are many optical components, and crystals are not easy to mass produce. At the same time, the alignment and coupling of optical components are complex, the packaging cost is high, and the performance stability is poor.

[0004] Patent CN103941516B, published on May 6, 2014, discloses an adjustable high-frequency pulse light source based on the carrier dispersion effect of a silicon-based microring resonator, with high output pulse stability and strong anti-interference ability; however, the ranging image refresh rate and ranging efficiency are poor. Summary of the invention

[0005] In order to overcome at least one defect in the above-mentioned prior art, the present invention provides a high-power soliton frequency comb chip and a pulse generation system and method thereof, which have a simple structure and realize multi-channel and high efficiency.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a high-power soliton frequency comb chip, including a substrate, a microring resonant cavity and a straight waveguide; the microring resonant cavity and the straight waveguide are both arranged on the top of the substrate; the straight waveguide includes a multimode waveguide, a multimode single-mode transition cone waveguide, a single-mode waveguide and a single-mode slot waveguide from one end to the other end, the wide end of the multimode single-mode transition cone is connected to the multimode waveguide, the narrow end of the multimode single-mode transition cone is connected to one end of the single-mode waveguide, and the other end of the single-mode waveguide is coupled to the single-mode lot waveguide through a linear strip-to-slot mode converter; the microring resonant cavity is located on one side of the multimode waveguide and is coupled to the multimode waveguide. The present invention combines the idea of ​​laser coherent ranging, uses the frequency comb microcavity structure integrated on the micro-nano waveguide, and performs on-chip optical amplification on the generated soliton frequency comb to achieve signal gain amplification, that is, the microring resonant cavity structure and the optical amplification single-mode slot waveguide structure are integrated on one chip, realizing a new integrated design of the ranging transmitter optical system. The rapid chirp of the pump laser within the range of the soliton frequency comb has an amplitude of up to several gigahertz and a scanning rate of up to ten megahertz. Rapid frequency changes will occur in the basic carrier waveform of the soliton pulse stream, but the pulse-to-pulse repetition rate of the soliton pulse stream remains unchanged. Therefore, the chirp emitted by a single narrow linewidth pump laser can be transmitted to all comb teeth of the soliton frequency comb chip at the same time, thereby realizing the parallelism of FMCW ranging. It solves the problems of low responsiveness, high power consumption, packaging cost and technical difficulty brought about by most of the time-of-flight ranging technology used in laser radars on the market, and provides a new scientific research concept.

[0007] In one embodiment, the core material of the micro-ring resonator is silicon nitride, doped with boron and phosphorus. Using silicon nitride as the structural material of the micro-ring resonator achieves ultra-low transmission loss of 0.5 dB / cm; compared with other materials such as silicon, it has higher transparency, ultra-low telecom wavelength two-photon absorption effect and smaller propagation loss. At the same time, the integration and integrated etching of the chip's waveguide structure greatly improve the coupling efficiency.

[0008] In one of the embodiments, a Bi-Al2O3\Er-Al2O3 precursor is deposited in the slit of the gain layer of the single-mode slot waveguide structure by atomic layer deposition technology. The new chirped signal passes through the optically amplified single-mode slot waveguide structure. Since the pump laser excites the gain layer to realize the up-conversion of rare earth ions, the radiation transition of the gain layer emits light with the same frequency and wavelength as the signal light, which greatly increases the signal light power by 15dB, providing a multi-channel, long-range (i.e., high-power) frequency comb pulse light source for the later use of linear chirp frequency modulation continuous laser ranging, so that the distance, speed and other physical information of the surrounding environment objects can be accurately and efficiently captured. In addition, the atomic layer deposition technology (ALD) is used to deposit the Bi-Al2O3\Er-Al2O3 precursor into the slit. This technology realizes high-concentration and high-activity deposition of rare earth ions to achieve effective amplification performance.

[0009] In one embodiment, the refractive index n of the soliton frequency comb waveguide chip is eff It is 1.99~2.01.

[0010] In one embodiment, the multimode waveguide has a thickness of 0.6um to 0.8um and a width of 1.7um to 4um.

[0011] In one embodiment, the thickness of the micro-ring resonant cavity is 0.6um to 0.8um, the micro-ring radius R of the micro-ring resonant cavity is 50um to 80um, the micro-ring width of the micro-ring resonant cavity is 1.5um to 1.9um, and the cavity free spectrum of the micro-ring resonant cavity is Wherein c=2.996*10^6m / s, and n is the cavity refractive index of the microring resonator.

[0012] In one embodiment, the width of the wide end of the multimode single-mode transition cone waveguide is 1.7um to 4um, and the width of the narrow end is 1.0um to 1.4um. The light field mode conversion is performed at the "wide end" and "narrow end" of the multimode single-mode transition cone waveguide.

[0013] In one embodiment, the thickness of the single-mode slot waveguide is 0.6um to 0.8um, and the width is 0.4um to 0.6um; the width of the slit slot is 0.1um to 0.5um.

[0014] The present invention also provides a pulse generation system, comprising a broadband laser, a pump laser diode, an arbitrary signal generator, an optoelectronic phase modulator, a wavelength division multiplexer, an optical circulator, a spectrometer; and the high-power soliton frequency comb chip described above; the output end of the broadband laser is connected to the light source input port of the electro-optical phase modulator, the waveform output port of the arbitrary signal generator is connected to the microwave signal input port of the optoelectronic phase modulator; the signal output port of the optoelectronic phase modulator is connected to the input port of the wavelength division multiplexer, the output port of the pump laser diode is connected to the input port of the wavelength division multiplexer; the output port of the wavelength division multiplexer is connected to the input end of the high-power soliton frequency comb chip, the output end of the high-power soliton frequency comb chip is connected to the input end of the optical circulator, and the output end of the optical circulator is connected to the spectrometer.

[0015] In the present invention, the signal laser is emitted by a broadband laser generator in the communication band of 1.1-1.6 μm. For example, triangular wave modulation is performed by any signal generator and electro-optic modulator to generate a signal laser with a specific periodic frequency. The signal laser is coupled to a wavelength division multiplexer together with a pump laser diode to achieve coupling of the signal light and the pump light. The signal laser then enters a high-power soliton frequency comb chip and forms a chirped frequency comb pulse required for coherent ranging under the modulation of the chip's microring resonant cavity.

[0016] Then, the generated pulsed laser passes through the slot amplification structure on the chip, namely the single-mode slot waveguide, and the on-chip / off-chip coupling is achieved through a multimode waveguide to improve the coupling efficiency. Once coupled, the multimode to single-mode multimode single-mode transition cone waveguide converts the multimode beam into a single-mode beam. Under the guidance of the single-mode waveguide, the single-mode beam is converted into a strip-to-linear strip-to-slot mode converter, where the mode is converted to be suitable for the next single-mode slot waveguide. Together with the erbium-doped aluminum oxide gain layer, the single-mode slot waveguide provides a means for effective on-chip amplification, achieving a net signal gain of approximately 10-15dB to meet the high power requirements of signal laser transmission and achieve a significant improvement in performance. Finally, after screening by the optical circulator, high-quality pulsed lasers can be monitored on the spectrometer.

[0017] The present invention also provides a pulse generation method, using the pulse generation system described above, comprising the following steps:

[0018] The broadband laser generator emits a signal laser, which is modulated by an arbitrary signal generator and an optoelectronic phase modulator to generate a signal laser with a specific periodic frequency;

[0019] The modulated signal laser is coupled to the wavelength division multiplexer together with the laser emitted by the pump laser diode to achieve the coupling of the signal light and the pump light;

[0020] The coupled laser is coupled into the high-power soliton frequency comb chip through a multimode waveguide; under the modulation of the micro-ring resonator of the high-power soliton frequency comb chip, a chirped frequency comb pulse laser required for coherent ranging is formed; then, the generated pulse laser passes through a multi-mode single-mode transition cone waveguide, and the multi-mode beam is converted into a single-mode beam through the multi-mode single-mode transition cone waveguide; under the guidance of the single-mode waveguide, the single-mode beam is converted into a strip beam and enters the linear strip-to-slot mode converter, and the strip beam is converted into a mode adapted to the single-mode slot waveguide through the linear strip-to-slot mode converter;

[0021] After the mode conversion, the signal laser enters the single-mode slot waveguide and realizes effective on-chip amplification under the action of the erbium-doped aluminum oxide gain layer, achieving a net signal gain of 10dB to 15dB to meet the high power requirements of signal laser transmission;

[0022] Finally, after the signal laser is filtered by the optical circulator, the pulse laser can be monitored on the spectrometer.

[0023] Compared with the prior art, the beneficial effects are:

[0024] 1. The light source is modulated by an arbitrary signal generator, and a single narrow-linewidth pump laser passes through the micro-ring resonator of the soliton frequency comb chip, and the chirp can be transmitted to all comb teeth of the soliton at the same time, which improves the image refresh rate of FMCW ranging by up to two orders of magnitude without damaging the eyes, and has good safety. In addition, the present invention can also be combined with a photon phase array based on a nanophotonic grating, providing a technical basis for miniaturized, massively parallel and ultra-high frame rate coherent lidar systems.

[0025] 2. The present invention innovatively combines the soliton frequency comb and the slot optical amplification structure, i.e., the combination of the micro-ring resonator and the single-mode slot waveguide, to achieve high-power soliton frequency comb pulse modulation and emission; when the signal light passes through the slot optical amplification structure, i.e., the single-mode slot waveguide, under the excitation of the pump laser, the gain material undergoes particle beam inversion and radiates the same laser as the signal light, achieving the amplification effect of the signal light. When the pump power reaches 4mW, the amplification effect can achieve a net gain of more than 15dB, achieving a meaningful amplification that can be practically applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the high-power soliton frequency comb chip of the present invention.

[0027] Figure 2 This is a top view of the high-power soliton frequency comb chip of the present invention.

[0028] Figure 3 It is a schematic diagram of the structure of the pulse generating system of the present invention.

[0029] Figure 4 It is a schematic diagram of the single-mode slot waveguide structure of the present invention.

[0030] Figure 5 It is the electric mode field distribution diagram of the present invention.

[0031] Figure 6 It is a time-domain-frequency-domain principle diagram of a chirped pulse in an embodiment of the present invention.

[0032] Figure 7 It is a principle diagram of frequency modulated continuous wave coherent ranging in an embodiment of the present invention.

[0033] Figure 8 It is the gain curve of the single-mode slot waveguide structure of the present invention. DETAILED DESCRIPTION

[0034] The drawings are only for illustrative purposes and should not be construed as limiting the present invention. To better illustrate the present embodiment, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are only for illustrative purposes and should not be construed as limiting the present invention.

[0035] like Figure 1 and Figure 2As shown, a high-power soliton frequency comb chip 1 includes a substrate 11, a microring resonant cavity 12 and a straight waveguide; the microring resonant cavity 12 and the straight waveguide are both arranged on the top of the substrate 11; the straight waveguide includes a multimode waveguide 13, a multimode single-mode transition cone waveguide 14, a single-mode waveguide 15 and a single-mode slot waveguide 17 from one end to the other end, the wide end of the multimode single-mode transition cone is connected to the multimode waveguide 13, the narrow end of the multimode single-mode transition cone is connected to one end of the single-mode waveguide 15, and the other end of the single-mode waveguide 15 is coupled to the single-mode lot waveguide through a linear strip-to-slot mode converter 16; the microring resonant cavity 12 is located on one side of the multimode waveguide 13 and is coupled to the multimode waveguide 13. The present invention combines the idea of ​​laser coherent ranging, uses the frequency comb microcavity structure to integrate on the micro-nano waveguide, and at the same time, performs on-chip optical amplification on the generated soliton frequency comb to achieve signal gain amplification, that is, the microring resonant cavity 12 structure and the optical amplification single-mode slot waveguide 17 structure are integrated on one chip, realizing a new integrated design of the ranging transmitter optical system. The rapid chirp of the pump laser within the range of the soliton frequency comb has an amplitude of up to several thousand MHz and a scanning rate of up to ten MHz. Rapid frequency changes will occur in the basic carrier waveform of the soliton pulse stream, but the pulse-to-pulse repetition rate of the soliton pulse stream remains unchanged. Therefore, the chirp emitted by a single narrow linewidth pump laser can be simultaneously transmitted to all comb teeth of the soliton frequency comb chip 1, thereby realizing the parallelism of FMCW ranging. It solves the problems of low responsiveness, high power consumption, packaging cost and technical difficulty brought about by most of the laser radars on the market using time-of-flight ranging technology, and provides a new scientific research concept.

[0036] Soliton frequency comb pulse generation and working principle: pump laser frequency ω p The agile chirp preserves the soliton state and causes all comb teeth ω ±μ Simultaneous chirping, where μ represents the mode number including the solitons. Figure 6 and Figure 7 The principle of massively parallel coherent lidar based on soliton microcomb is explained. The basic idea is to transfer the chirp of a prepared frequency modulated laser source to multiple comb sidebands by using modulated laser to generate dissipative Kerr solitons (DKS). In the time domain, see Figure 6 As shown, the underlying soliton carrier frequency is modulated while minimizing variations in the pulse envelope and repetition rate. In the frequency domain, this is equivalent to modulating the optical frequency of each comb tooth simultaneously around its mean (i.e., modulating the carrier envelope frequency of the frequency comb). When combined with triangular frequency modulation of a narrow linewidth pump laser, this effect generates a massively parallel array of independent FMCW lasers.

[0037] Next, a linear chirp signal is transmitted to an object, and the time-frequency information of the return signal is determined by delayed homodyne detection. Assuming a triangular laser scan, with a period of T over an offset bandwidth of B; the distance information (i.e., flight time Δt) is mapped to the beat note frequency F, i.e.:

[0038] F = Δt × 2B / T, (for static objects)

[0039] Due to the object's relative velocity v, the returning laser light is detected with a Doppler shift:

[0040] Δf=k·v / π

[0041] where k is the wave vector and v is the velocity of the illuminated object. As a result, the homodyne return signal of a moving object consists of two frequencies for the upward and downward laser scans, f and u 、f d Right now:

[0042] f u =F+Δf D , f d =|-F+Δf D |

[0043] Δf D is the frequency offset, then the distance s and speed v of the measured object are expressed as:

[0044]

[0045]

[0046] where f c is the laser frequency, cosθ is the signal laser scanning angle;

[0047] By using a low-bandwidth detector and a digitizer to zero out the reflected signals of the original comb teeth channel by channel, the coherent ranging signal can be recovered and reconstructed simultaneously, thereby obtaining the offset of each comb line and giving the speed and distance (s offset, v offset) of each pixel.

[0048] In one embodiment, the core material of the micro-ring resonator 12 is silicon nitride, doped with boron and phosphorus. Silicon nitride is used as the structural material of the micro-ring resonator 12 to achieve ultra-low transmission loss of 0.5 dB / cm; compared with other materials such as silicon, it has higher transparency, ultra-low telecom wavelength two-photon absorption effect and smaller propagation loss, and the integration and integrated etching of the chip's waveguide structure greatly improve the coupling efficiency.

[0049] In one embodiment, Bi-Al2O3\Er-Al2O3 precursors are deposited in the slit of the gain layer of the single-mode slot waveguide 17 structure by atomic layer deposition technology. The new chirped signal passes through the optically amplified single-mode slot waveguide 17 structure. Since the pump laser excites the gain layer to achieve up-conversion of rare earth ions, the gain layer radiates and transitions to emit light with the same frequency and wavelength as the signal light, which greatly increases the signal light power by 15 dB. Figure 8 As shown, it provides a multi-channel, long-range (i.e., high-power) frequency comb pulse light source for the later use of linear chirp frequency modulation continuous laser ranging, so that the physical information such as the distance and speed of the surrounding objects can be accurately and efficiently captured. In addition, the atomic layer deposition technology (ALD) is used to deposit the Bi-Al2O3\Er-Al2O3 precursor into the slit. This technology realizes high-concentration and high-activity deposition of rare earth ions to achieve effective amplification performance.

[0050] The influence of waveguide structure on signal light gain mainly includes two aspects: first, the transmission loss of waveguide. Due to process limitations, the sidewalls and end faces of optical waveguides are rough and difficult to be smooth enough. They also have a certain absorption effect on the light field energy, resulting in absorption loss. Therefore, the preparation of waveguide structure needs to reduce its own absorption and transmission loss as much as possible. Through technical improvements, photolithography waveguide technology has achieved a low transmission loss of 0.5dB / cm. SiO2 is deposited on wafers and Si3N4 is grown. The slot waveguide amplification structure is prepared through coating, masking, electron beam lithography, degumming, and ALD deposition. Second, the geometric size and structure of the optical waveguide have a limiting effect on the distribution of the light field in the waveguide. The rare earth doped optical waveguide amplifier (EDWA) structure is mainly divided into two parts, the passive area and the active area. Here, the passive area uses materials with relatively high refractive index such as Si3N4, and the active area uses optically active rare earth ion materials such as erbium and bismuth to form a gain layer. From the perspective of energy, pump light is injected into the waveguide to excite ions from the ground state to a high energy level, and then stimulated radiation produces photons with exactly the same frequency, phase, propagation direction and polarization state, which are superimposed on the signal light to produce light amplification. In general, the energy of the pump light is transferred to the signal light. Therefore, by designing and optimizing the waveguide structure, the proportion of the energy of the pump light and the signal light in the active area can be increased, and more pump light energy can be transferred, thereby increasing the gain of the amplifier.

[0051] The parameter that measures the energy distribution of the light field in the waveguide is called the energy limiting factor Γ, which is defined as the ratio of the optical field energy in the active region Ω to the energy in the waveguide cross-sectional space S. It is solved by integration. The larger the Γ value, the more conducive it is to light amplification. Therefore, the purpose of waveguide structure design and optimization is to obtain the largest possible Γ.

[0052]

[0053] The transmission of electromagnetic fields is subject to Maxwell's equations. By solving the equations, we can naturally obtain the distribution of the field in the slit and waveguide. When two silicon waveguides with very small widths are close to a sub-micron or smaller distance, the electric field at the interface between the waveguide and the slit undergoes strong coupling resonance, which greatly enhances the electric field in the entire active nano-slit region. Specifically, at the interface, Figure 4 As shown, n S 、n H 、n C They are the refractive index of the three parts of waveguide material\slit material\cladding, and the electric displacement vector Continuity, that is:

[0054]

[0055]

[0056] Where ε0 is the dielectric constant of vacuum, is the vector electric field of the waveguide and the slit; this electric field appears when it enters the slit from the waveguide The electric field in the slit area increases due to the sudden change of H , high H becomes an important structural parameter affecting the energy limiting factor Γ.

[0057] In addition to optimizing the waveguide structure design, how to increase the doping concentration of rare earth ions, increase the excited state lifetime, achieve a higher population inversion in a specific band, and ultimately obtain a higher net gain. By using erbium and bismuth co-doping and ALD atomic layer deposition technology to control the growth process at the atomic scale, the solubility concentration of rare earth ions in the material can reach 10 21 / cm 3 , and maintain good optical activity, ultimately achieving a net gain of 15dB. This design is compatible with traditional CMOS processes and also provides a guarantee for later product manufacturing.

[0058] In one embodiment, the refractive index n of the soliton frequency comb waveguide chip is eff It is 1.99~2.01.

[0059] In one embodiment, the thickness of the multimode waveguide 13 is 0.6um to 0.8um, and the width is 1.7um to 4um. The thickness of the microring resonant cavity 12 is 0.6um to 0.8um, the radius R of the microring resonant cavity 12 is 50um to 80um, the width of the microring resonant cavity 12 is 1.5um to 1.9um, and the cavity free spectrum of the microring resonant cavity 12 is Where c = 2.996*10^6m / s, n is the cavity refractive index of the micro-ring resonator 12. The width of the wide end of the multi-mode single-mode transition cone waveguide 14 is 1.7um to 4um; the width of the narrow end is 1.0um to 1.4um. The light field mode conversion is performed at the "wide end" and "narrow end" of the multi-mode single-mode transition cone waveguide 14. The thickness of the single-mode slot waveguide 17 is 0.6um to 0.8um, and the width is 0.4um to 0.6um; the width of the slit slot is 0.1um to 0.5um.

[0060] In another embodiment, the present invention further provides a pulse generating system, comprising a broadband laser 2, an arbitrary signal generator 3, an optoelectronic phase modulator 4, a pump laser diode 5, a wavelength division multiplexer 6, an optical circulator 7, a spectrometer 8; and the above soliton frequency comb chip 1; the output end of the broadband laser 2 is connected to the light source input port of the electro-optical phase modulator, and the waveform output port of the arbitrary signal generator 3 is connected to the microwave signal input port of the optoelectronic phase modulator 4; the signal output port of the optoelectronic phase modulator 4 is connected to the input port of the wavelength division multiplexer 6, and the output port of the pump laser diode 5 is connected to the input port of the wavelength division multiplexer 6; the output port of the wavelength division multiplexer 6 is connected to the input end of the soliton frequency comb chip 1, the output end of the soliton frequency comb chip 1 is connected to the input end of the optical circulator 7, and the output end of the optical circulator 7 is connected to the spectrometer 8.

[0061] In the present invention, the signal laser is emitted by a broadband laser 2, the wavelength of which is in the communication band of 1100-1600 μm, and is modulated by an arbitrary signal generator 3 and an electro-optic modulator, for example, a triangular wave, to generate a signal laser with a specific periodic frequency, and is coupled to a wavelength division multiplexer 6 together with a pump laser diode 5 to achieve coupling of the signal light and the pump light, and then enters the soliton frequency comb chip 1, and under the modulation of the chip microring resonator 12, a chirped frequency comb pulse required for coherent ranging is formed.

[0062] Then, the generated pulsed laser passes through the slot amplification structure on the chip, namely the single-mode slot waveguide 17. The on-chip / off-chip coupling is achieved through the multimode waveguide 13 to improve the coupling efficiency. Once coupled, the multimode to single-mode multimode single-mode transition cone waveguide 14 converts the multimode beam into a single-mode beam. Under the guidance of the single-mode waveguide 15, the single-mode beam is converted into a strip-to-linear strip-to-slot mode converter 16, where the mode is converted to be suitable for the subsequent single-mode slot waveguide 17. Together with the erbium-doped aluminum oxide gain layer, the single-mode slot waveguide 17 provides a means for effective on-chip amplification, achieving a net signal gain of about 10-15dB to meet the high power requirements of signal laser transmission and achieve a significant improvement in performance. Finally, after screening by the optical circulator 7, high-quality pulsed lasers can be monitored on the spectrometer 8.

[0063] In another embodiment, the present invention further provides a pulse generation method, using the above pulse generation system, comprising the following steps:

[0064] The broadband laser generator emits a signal laser, which is modulated by an arbitrary signal generator 3 and an optoelectronic phase modulator 4 to generate a signal laser with a specific periodic frequency;

[0065] The modulated signal laser is coupled to the wavelength division multiplexer 6 together with the laser emitted by the pump laser diode 5, so as to achieve the coupling of the signal light and the pump light;

[0066] The coupled laser is coupled into the soliton frequency comb chip 1 through the multimode waveguide 13; under the modulation of the micro-ring resonator 12 of the soliton frequency comb chip 1, a chirped frequency comb pulse laser required for coherent ranging is formed; then, the generated pulse laser passes through the multi-mode single-mode transition cone waveguide 14, and the multi-mode light beam is converted into a single-mode light beam through the multi-mode single-mode transition cone waveguide 14; under the guidance of the single-mode waveguide 15, the single-mode light beam is converted into a strip light beam and enters the linear strip-to-slot mode converter 16, and the strip light beam is converted into a mode adapted to the single-mode slot waveguide 17 through the linear strip-to-slot mode converter 16;

[0067] After the mode conversion, the signal laser enters the single-mode slot waveguide 17, and under the action of the erbium-doped aluminum oxide gain layer, effective on-chip amplification is achieved, achieving a signal net gain of 10dB to 15dB to meet the high power requirements of signal laser transmission;

[0068] Finally, after the signal laser is screened by the optical circulator 7 , the pulse laser can be monitored on the spectrometer 8 .

[0069] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0070] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0071] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0073] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0074] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0075] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A pulse generating system, characterized in that: The invention comprises a broadband laser (2), an arbitrary signal generator (3), an optoelectronic phase modulator (4), a pump laser diode (5), a wavelength division multiplexer (6), an optical circulator (7), a spectrometer (8), and a soliton frequency comb chip (1); the output end of the broadband laser (2) is connected to the light source input port of the electro-optical phase modulator, the waveform output port of the arbitrary signal generator (3) is connected to the microwave signal input port of the optoelectronic phase modulator (4); the signal output port of the optoelectronic phase modulator (4) is connected to the input port of the wavelength division multiplexer (6), the output port of the pump laser diode (5) is connected to the input port of the wavelength division multiplexer (6); the output port of the wavelength division multiplexer (6) is connected to the input end of the soliton frequency comb chip (1), the output end of the soliton frequency comb chip (1) is connected to the input end of the optical circulator (7), and the output end of the optical circulator (7) is connected to the spectrometer (8). The soliton frequency comb chip (1) comprises a substrate (11), a microring resonant cavity (12) and a straight waveguide; the microring resonant cavity (12) and the straight waveguide are both arranged on the top of the substrate (11); the straight waveguide comprises, from one end to the other end, a multimode waveguide (13), a multimode single-mode transition cone waveguide (14), a single-mode waveguide (15) and a single-mode slot waveguide (17); the wide end of the multimode single-mode transition cone is connected to the multimode waveguide (13); The narrow end of the multimode single-mode transition cone is connected to one end of a single-mode waveguide (15), and the other end of the single-mode waveguide (15) is coupled to a single-mode slot waveguide (17) via a linear strip-to-slot mode converter (16); the micro-ring resonant cavity (12) is located on one side of the multi-mode waveguide (13) and is coupled to the multi-mode waveguide (13); the core material of the micro-ring resonant cavity (12) is silicon nitride, and is doped with boron and phosphorus.

2. The pulse generating system according to claim 1, characterized in that: A Bi-Al2O3\Er-Al2O3 precursor is deposited in the slit of the gain layer of the single-mode slot waveguide (17) structure by atomic layer deposition technology.

3. The pulse generating system according to claim 1, characterized in that: Refractive index n of the soliton frequency comb chip eff It is 1.99~2.

01.

4. The pulse generating system according to any one of claims 1 to 3, characterized in that: The multimode waveguide (13) has a thickness of 0.6um to 0.8um and a width of 1.7um to 4um.

5. The pulse generating system according to claim 4, characterized in that: The thickness of the micro-ring resonant cavity (12) is 0.6um to 0.8um, the micro-ring radius R of the micro-ring resonant cavity (12) is 50um to 80um, the micro-ring width of the micro-ring resonant cavity (12) is 1.5um to 1.9um, and the cavity free spectrum of the micro-ring resonant cavity (12) is Wherein c=2.996*10^6m / s, and n is the cavity refractive index of the micro-ring resonant cavity (12).

6. The pulse generating system according to claim 4, characterized in that: The width of the wide end of the multi-mode single-mode transition cone waveguide (14) is 1.7um-4um; the width of the narrow end is 1.0um-1.4um.

7. The pulse generating system according to claim 4, characterized in that: The thickness of the single-mode slot waveguide (17) is 0.6um to 0.8um, and the width is 0.4um to 0.6um; the width of the slit slot is 0.1um to 0.5um.

8. A pulse generation method, characterized in that: Using the pulse generating system of claim 1, comprising the following steps: The broadband laser generator emits a signal laser, which is modulated by an arbitrary signal generator (3) and an optoelectronic phase modulator (4) to generate a signal laser with a specific periodic frequency; The modulated signal laser light is coupled together with the laser light emitted by the pump laser diode (5) into a wavelength division multiplexer (6) to achieve coupling of the signal light and the pump light; The coupled laser is coupled into the soliton frequency comb chip (1) through a multimode waveguide (13); under the modulation of the micro-ring resonant cavity (12) of the soliton frequency comb chip (1), a chirped frequency comb pulse laser required for coherent ranging is formed; then, the generated pulse laser passes through a multimode single-mode transition cone waveguide (14), and the multimode light beam is converted into a single-mode light beam through the multimode single-mode transition cone waveguide (14); under the guidance of the single-mode waveguide (15), the single-mode light beam is converted into a strip light beam and enters a linear strip-to-slot mode converter (16), and the strip light beam is converted into a mode compatible with the single-mode slot waveguide (17) through the linear strip-to-slot mode converter (16); After the mode conversion, the signal laser enters the single-mode slot waveguide (17), and under the action of the erbium-doped aluminum oxide gain layer, effective on-chip amplification is achieved, achieving a signal net gain of 10 dB to 15 dB to meet the high power requirement of signal laser transmission; Finally, after the signal laser is screened by the optical circulator (7), the pulse laser can be monitored on the spectrometer (8).

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