Electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser and frequency stabilization method

Abstract

The present application relates to an electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser and a frequency stabilization method, which includes: an input component for generating a first laser signal; a phase shifter for receiving the first laser signal transmitted by the input component and, under preset conditions, phase-shifting the first laser signal to obtain a second laser signal; an electrically tunable filter feedback component for receiving the second laser signal, filtering the second laser signal to obtain a narrow-spectrum optical signal, and electrically tuning the first laser signal under preset conditions; an atomic frequency discrimination system for receiving the narrow-spectrum optical signal to generate a frequency discrimination signal; and a controller for adjusting the voltage of the tuning electrodes of the phase shifter and the electrically tunable filter feedback structure based on the frequency discrimination signal to stabilize the frequency. This method solves the problems of existing thermally phase-tuned, integrated external cavity, narrow-linewidth, frequency-stable lasers, such as slow tuning response speed or high power loss, which lead to extended time from discrimination to frequency shift and low frequency discrimination signal strength, which greatly affects the frequency stabilization effect.

Description

Technical Field

[0001] The present application relates to the technical field of laser frequency stabilization, and in particular to an electrically phase-modulated narrow-linewidth, high-frequency-stable integrated external cavity laser and a frequency stabilization method. Background Art

[0002] In recent years, with the development of quantum technology based on atomic physics mechanisms, high-precision timing, detection and navigation are becoming new hot research directions. Since the implementation schemes of high-precision devices often involve the hyperfine structure of atoms, existing research often requires narrow-linewidth and high-frequency-stable semiconductor diode lasers to provide pump light to induce interference, hyperfine energy level transitions, coherent population trapping and other atomic physics mechanisms. For example, in the field of high-precision timing, optical clock devices require narrow-linewidth and high-frequency-stable lasers to lock with alkali metal atomic clock transitions to provide an ultra-stable frequency reference for clock signal generation. For example, in the field of high-precision detection, coherent population trapped atomic magnetometers detect weak magnetic fields based on the Zeeman effect, and require two beams of pump light with different frequencies to induce the coherent population trapping phenomenon. Improving the stability of the laser is conducive to improving the signal-to-noise ratio of the magnetic detection signal.

[0003] Similarly, in the field of high-precision navigation, gyroscopes, as inertial devices, play a key role in autonomous navigation. Quantum gyroscopes, as the gyroscopes with the highest resolution currently available, perform coherent detection of phase changes caused by inertial forces based on the principle of atomic interference. This process is highly sensitive to frequency and requires a narrow-linewidth, highly stable laser to achieve this.

[0004] It can be seen that the narrow-linewidth and high-frequency-stable laser has broad application prospects as one of the basic devices in many practical fields such as autonomous timing, aeromagnetic and geomagnetic measurement, and inertial navigation.

[0005] For this type of laser, the core performance indicators are linewidth and frequency stability. Ordinary Fabry-Perot cavity diode lasers are often affected by various spectral line broadening mechanisms and environmental thermal disturbances, and have linewidths and low frequency stability in the GHz range, making it impossible to stably output precise frequencies. In addition, the laser frequency tuning based on the die temperature also affects the temperature of the active region, bringing uncertainty to characteristics such as output power, which is not conducive to meeting the frequency stabilization requirements. The integrated external cavity laser solution has the advantages of narrow linewidth and good frequency tunability, and is one of the mainstream solutions for achieving narrow linewidth and high-frequency stability lasers.

[0006] Common external cavity narrow linewidth laser solutions are mainly based on silicon-based or silicon nitride-based external cavity platforms, and adjust the laser's lasing frequency based on thermo-optical tuning. However, the response speed of thermo-optical tuning severely limits the speed of frequency tuning, which in turn limits the laser's frequency stabilization characteristics. In recent years, the technology for preparing thin-film lithium niobate substrates using methods such as smart-cut has gradually matured. Since lithium niobate material has a wide transparency window of 0.4-5μm and a high first-order electro-optical coefficient, its excellent optoelectronic properties provide new solutions for application fields such as waveguide modulators and tunable microring external cavities.

[0007] However, the existing thin-film lithium niobate external cavity narrow-linewidth laser fails to meet the needs of the frequency stabilization system. It has defects such as easy mode hopping or large power loss, which limits the frequency tuning range and causes highly unstable frequency. It also easily leads to low discrimination signal strength, reducing the frequency stabilization effect, which urgently needs to be solved. Summary of the Invention

[0008] The present application provides an electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser and a frequency stabilization method to address the problems of existing thermally phase-tuned, integrated external cavity, narrow-linewidth, frequency-stable lasers, such as slow tuning response speed or large power loss, which lead to extended time from frequency discrimination to frequency shift and low frequency discrimination signal strength, greatly affecting the frequency stabilization effect.

[0009] In a first aspect, an embodiment of the present application provides an electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser, comprising: an input component for generating a first laser signal; a phase shifter for receiving the first laser signal transmitted by the input component and, under preset conditions, phase-shifting the first laser signal to obtain a second laser signal; an electrically tunable filter feedback component for receiving the second laser signal transmitted by the phase shifter, filtering the second laser signal and feeding it back to the input component to obtain a narrow-spectrum optical signal, and electrically tuning the first laser signal under the preset conditions; an atomic frequency discrimination system for receiving the narrow-spectrum optical signal output by the electrically tunable filter feedback component and generating a frequency discrimination signal; and a controller for adjusting, based on the frequency discrimination signal and according to a preset control strategy, the tuning electrode voltages of the phase shifter and the electrically tunable filter feedback component to change the frequency of the first laser signal until the first laser signal reaches a preset frequency-stable condition.

[0010] Optionally, in one embodiment of the present application, the phase shifter and the electrically tunable filter feedback component are composed of a straight waveguide and a curved waveguide prepared on a thin-film lithium niobate platform based on a lithium niobate thin film substrate.

[0011] Optionally, in one embodiment of the present application, the input component includes: a gain chip, used to generate the first laser signal; and a mode spot size conversion structure, used to transmit the first laser signal according to a preset loss rate.

[0012] Optionally, in one embodiment of the present application, it further includes: a waveguide coupler for transmitting optical signals between the gain chip and the electrically tunable filter feedback component, and transmitting the narrow-spectrum optical signal to the atomic frequency discrimination system.

[0013] Optionally, in one embodiment of the present application, the phase shifter and the electrically tunable filter feedback component are composed of a straight waveguide and a curved waveguide prepared on a thin-film lithium niobate platform based on a lithium niobate thin film substrate.

[0014] A second aspect of the present application provides a frequency stabilization method for an electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser, comprising the following steps: generating a first laser signal; phase-shifting the first laser signal under the preset conditions to obtain a second laser signal; filtering the second laser signal to obtain a narrow-spectrum optical signal, and electrically tuning the first laser signal under the preset conditions, and generating a frequency discrimination signal based on the narrow-spectrum optical signal; and adjusting, based on the frequency discrimination signal, the tuning electrode voltages of the phase shifter and the electrically tuned filter feedback component according to the preset control strategy to change the frequency of the first laser signal until the first laser signal reaches the preset frequency stabilization condition.

[0015] Optionally, in one embodiment of the present application, the phase shifter and the electrically tunable filter feedback component are composed of a straight waveguide and a curved waveguide prepared on a thin-film lithium niobate platform based on a lithium niobate thin film substrate.

[0016] Optionally, in one embodiment of the present application, generating the first laser signal includes: generating the first laser signal based on the gain chip; and transmitting the first laser signal through the mode spot size transformation structure according to a preset loss rate.

[0017] Optionally, in one embodiment of the present application, it further includes: using the waveguide coupler to transmit the optical signal between the gain chip and the electrically tunable filter feedback component, and transmitting the narrow-spectrum optical signal to the atomic frequency discrimination system.

[0018] In a third aspect, an embodiment of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the frequency stabilization method for the electrically phase-adjusted narrow-linewidth, high-frequency-stable integrated external cavity laser as described in the above embodiment.

[0019] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the frequency stabilization method of the electrically phase-adjusted narrow-linewidth, high-frequency-stable integrated external cavity laser as described above.

[0020] Therefore, the embodiments of the present application have the following beneficial effects:

[0021] Embodiments of the present application may include an input component for generating a first laser signal; a phase shifter for receiving the first laser signal transmitted by the input component and, under preset conditions, phase-shifting the first laser signal to obtain a second laser signal; an electrically tunable filter feedback component for receiving the second laser signal transmitted by the phase shifter, filtering the second laser signal and feeding it back to the input component to obtain a narrow-spectrum optical signal, and electrically tuning the first laser signal under preset conditions; an atomic frequency discrimination system for receiving the narrow-spectrum optical signal output by the electrically tunable filter feedback component and generating a frequency discrimination signal; a controller for adjusting the tuning electrode voltages of the phase shifter and the electrically tunable filter feedback component based on the frequency discrimination signal and according to a preset control strategy to change the frequency of the first laser signal until the first laser signal reaches a preset frequency stabilization condition. The embodiment of the present application can combine the optimized electrically tunable filter feedback external cavity into the frequency discrimination and frequency stabilization system, and use the low power loss and high-speed electro-optical tuning of the thin film lithium niobate external cavity to realize a small-sized electrically phase-tuned narrow-linewidth high-frequency-stabilized integrated external cavity laser, thereby solving the design defects of the thermal phase-tuned micro-ring external cavity, and can give full play to the high tuning speed advantage of electro-optical tuning, reduce the response time of the frequency stabilization system from receiving the discrimination signal to adjusting the lasing frequency, and further improve the frequency stability of the laser. Thus, it solves the defects of the existing thermal phase-tuned integrated external cavity narrow-linewidth frequency-stabilized laser, such as slow tuning response speed or large power loss, which leads to extended time from discrimination to frequency shift and low discrimination signal strength, which greatly affects the frequency stabilization effect. The additional aspects and advantages of the present application will be partially given in the following description, and some will become obvious from the following description, or be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0023] Figure 1 This is an example diagram of an electrically phase-tuned, narrow-linewidth, and highly frequency-stable integrated external cavity laser according to an embodiment of the present application;

[0024] Figure 2 A schematic diagram of the structure of an electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser with an all-pass filtering micro-ring provided in one embodiment of the present application;

[0025] Figure 3 A schematic diagram of a dual-ring resonant spectrum alignment provided in one embodiment of the present application;

[0026] Figure 4 A schematic diagram of the structure of an electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser without an all-pass filtering micro-ring is provided as an embodiment of the present application;

[0027] Figure 5 This is a flow chart of a frequency stabilization method for an electrically phase-modulated, narrow-linewidth, and highly frequency-stable integrated external cavity laser according to an embodiment of the present application;

[0028] Figure 6 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application.

[0029] Among them, 10-electrically phase-tuned narrow-linewidth and high-frequency-stable integrated external cavity laser, 100-input component, 101-gain chip, 102-mode spot size transformation structure, 200-phase shifter, 300-electrically adjustable filter feedback component, 301-all-pass filter microring, 302-upload and download feedback microring, 400-atomic frequency discrimination system, 500-controller, 600-waveguide coupler, 601-memory, 602-processor, 603-communication interface. DETAILED DESCRIPTION

[0030] The following describes in detail embodiments of the present application, 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 application, and should not be construed as limiting the present application.

[0031] The following describes an electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser and a frequency stabilization method according to an embodiment of the present application with reference to the accompanying drawings. In response to the problems mentioned in the above background technology, the present application provides an electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser, comprising an input component for generating a first laser signal; a phase shifter for receiving the first laser signal transmitted by the input component and, under preset conditions, phase-shifting the first laser signal to obtain a second laser signal; an electrically tunable filter feedback component for receiving the second laser signal transmitted by the phase shifter, filtering the second laser signal and feeding it back to the input component to obtain a narrow-spectrum optical signal, and electrically tuning the first laser signal under preset conditions; an atomic frequency discrimination system for receiving the narrow-spectrum optical signal output by the electrically tunable filter feedback component and generating a frequency discrimination signal; a controller for adjusting the tuning electrode voltages of the phase shifter and the electrically tunable filter feedback component according to a preset control strategy based on the frequency discrimination signal to change the frequency of the first laser signal until the first laser signal reaches a preset frequency stabilization condition. The embodiments of the present application can integrate an optimized electrically tunable filter feedback external cavity into a frequency discrimination and frequency stabilization system. Utilizing a thin-film lithium niobate external cavity with low power loss and high-speed electro-optical tuning, a small-sized electrically phase-tuned narrow-linewidth, high-frequency-stabilization integrated external cavity laser is realized. This overcomes the design flaws of the thermally phase-tuned micro-ring external cavity, fully leveraging the high tuning speed advantage of electro-optical tuning, reducing the response time of the frequency stabilization system from receiving the discrimination signal to adjusting the lasing frequency, and further improving the frequency stability of the laser. This solves the problems of existing thermally phase-tuned integrated external cavity narrow-linewidth frequency-stabilization lasers, such as slow tuning response speed or high power loss, which lead to extended time from discrimination to frequency shift and low discrimination signal strength, significantly affecting the frequency stabilization effect.

[0032] Specifically, Figure 1 Schematic block diagram of an electrically phase-tuned, narrow-linewidth, and highly frequency-stable integrated external cavity laser according to an embodiment of the present application.

[0033] like Figure 1 As shown, the electrically phase-tuned narrow-linewidth high-frequency-stable integrated external cavity laser 10 includes: an input component 100 , a phase shifter 200 , an electrically tunable filter feedback component 300 , an atomic frequency discrimination system 400 and a controller 500 .

[0034] The input component 100 is used to generate a first laser signal.

[0035] In the embodiments of the present application, the input component can be used as a light source to generate an initial laser signal and transmit the signal to provide reliable signal data for subsequent laser frequency stabilization.

[0036] Optionally, in one embodiment of the present application, the input component 100 includes: a gain chip and a mode spot size transformation structure.

[0037] The gain chip is used to generate a first laser signal.

[0038] The mode spot size conversion structure is used to transmit the first laser signal according to a preset loss rate.

[0039] It should be noted that, in the embodiment of the present application, the above-mentioned input component includes a gain chip and a mode spot size transformation structure.

[0040] The gain chip's lasing wavelength is in the 0.4-5μm band. One end features a high-reflectivity coating (reflectivity ≥ 90%), while the other end features a low-reflectivity coating (reflectivity ≤ 0.1%). The structure is a ridge waveguide with index-guided lasing, resulting in an output light tilt angle ranging from 0° to 10° relative to the horizontal. This wavelength band covers the wavelengths of various alkali metal atomic clock transitions, such as Yb (578nm), Ca (657nm), Sr (698nm), Rb (780.24nm), and Cs (852nm).

[0041] The output end of the gain chip is connected to the input end of the mode spot size conversion structure. Since the light spot size of the light source, that is, the gain chip, is much larger than the waveguide mode field size, the embodiments of the present application can transmit the generated initial laser to the external cavity waveguide with low loss through the mode spot size conversion structure.

[0042] Therefore, the embodiments of the present application generate and efficiently transmit light through input components such as the gain chip and the mode spot size conversion structure, effectively ensuring the subsequent frequency stabilization of the laser.

[0043] The phase shifter 200 is used to receive the first laser signal transmitted by the input component 100 and, under a preset condition, perform phase shifting on the first laser signal to obtain a second laser signal.

[0044] In an embodiment of the present application, the output end of the above-mentioned mode spot size conversion structure is connected to the input end of the phase shifter, so as to perform phase shift on the laser signal output by the mode spot size conversion structure.

[0045] The electrically tunable filter feedback component 300 is used to receive the second laser signal transmitted by the phase shifter 200, filter the second laser signal and feed it back to the input component 100 to obtain a narrow-spectrum optical signal, and electrically tune the first laser signal under preset conditions;

[0046] It should be noted that in the embodiments of the present application, the phase shifter and the electrically tunable filter feedback component (or electrically tunable filter feedback structure) are composed of an on-chip microstructure based on a thin-film lithium niobate platform, and the local refractive index of the structure can be electrically tuned based on the electro-optical effect of lithium niobate.

[0047] Among them, the electrically tunable filter feedback component is composed of a combined microring or other on-chip microstructures with bandpass filtering characteristics. The output spectrum of the output port of the above-mentioned electrically tunable filter feedback component is the spectrum of the incident spectrum of the input port after bandpass filtering. The half-maximum width of the bandpass filter resonance peak of the electrically tunable filter feedback component is not higher than 1 / 1000 of the half-maximum width of the gain spectrum of the gain chip, thereby achieving linewidth narrowing through narrow spectrum feedback to the gain chip cavity.

[0048] Optionally, in one embodiment of the present application, the phase shifter 200 and the electrically tunable filter feedback component 300 are composed of a straight waveguide and a curved waveguide prepared on a thin-film lithium niobate platform based on a lithium niobate thin film substrate.

[0049] In addition, the phase shifter and electrically tunable filter feedback structure in the embodiments of the present application have tuning electrodes based on the electro-optical effect of lithium niobate. The phase shifter electrode can be used to fine-tune the lasing frequency, and the electrically tunable filter feedback structure electrode can be used to coarsely tune the resonant peak position through electrical tuning, so that the lasing center frequency is aligned with the atomic transition spectrum line of the micro-gas chamber.

[0050] The above-mentioned on-chip microstructure based on the thin-film lithium niobate platform can be composed of straight waveguides and curved waveguides prepared on the lithium niobate thin film substrate. The waveguide form can be a strip waveguide, a ridge waveguide, or a loaded waveguide or a guided ridge waveguide of heterogeneously integrated silicon nitride / silicon oxide strips.

[0051] Therefore, the embodiments of the present application can achieve rapid electro-optical tuning of the lasing frequency through the phase shifter on the external cavity chip and the electrically tunable filter feedback component electrode. At the same time, compared with the thermal tuning material platform, the frequency stabilization system based on the external cavity of the thin film lithium niobate platform in the embodiments of the present application can effectively improve the tuning speed and frequency stability.

[0052] The atomic frequency discrimination system 400 is used to receive the narrow spectrum optical signal output by the electrically tunable filter feedback component 300 and generate a frequency discrimination signal.

[0053] Furthermore, the embodiments of the present application can also input the narrow-spectrum optical signal output by the above-mentioned electrically tunable filter feedback component into the atomic frequency discrimination system. The atomic frequency discrimination system generates a corresponding discrimination signal based on the narrow-spectrum optical signal, providing a basis for the subsequent controller to adjust the tuning electrode voltage of the phase shifter and the electrically tunable filter feedback component.

[0054] Optionally, in one embodiment of the present application, the electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser 10 of the embodiment of the present application further includes: a waveguide coupler for transmitting optical signals between the gain chip and the electrically tunable filter feedback component, and transmitting the narrow-spectrum optical signal to the atomic frequency discrimination system.

[0055] In an embodiment of the present application, the above-mentioned waveguide coupler is a 2×2 waveguide coupler, which has three functions: transmitting the output light of the gain chip to the electrically tunable filter feedback component, feeding back the output light of the electrically tunable filter feedback component into the gain chip cavity, and leading out the narrow linewidth output light to the atomic frequency discrimination system.

[0056] In the specific implementation process, those skilled in the art may also adopt a lithium niobate ridge waveguide directional coupler with a power separation ratio close to 50:50, or other devices or device groups with the above three functions according to actual conditions, without specific limitation here.

[0057] It should be noted that in an embodiment of the present application, the output end of the above-mentioned phase shifter is connected to the first left port of the 2×2 waveguide coupler, an electrically tunable filter feedback component is arranged between the first and second right ports of the 2×2 waveguide coupler, and the output light is emitted along the second left port of the 2×2 waveguide coupler and connected to the atomic frequency discrimination system.

[0058] It should be noted that the single unidirectional transmission between the input port and the output port of the electronically tunable filter feedback component experiences no more than three waveguide couplings. On the basis of ensuring single-mode and narrow-bandpass filtering, unnecessary waveguide coupling losses are minimized and the lasing power is increased.

[0059] Therefore, the embodiment of the present application reduces the number of waveguide couplings experienced during a single laser feedback process to less than three times by adopting a 2×2 waveguide coupler and a loss-controlled electrically tunable filter feedback component, thereby effectively improving the power loss caused by coupling.

[0060] The controller 500 is used to adjust the tuning electrode voltages of the phase shifter 200 and the electrically tunable filter feedback component 300 based on the frequency discrimination signal and according to a preset control strategy to change the frequency of the first laser signal until the first laser signal reaches a preset stable frequency condition.

[0061] In the embodiment of the present application, the corresponding control circuit can be used as a controller, and the controller is connected to the output end of the atomic frequency discrimination system, so that the controller receives the frequency discrimination signal;

[0062] At the same time, the output end of the controller is connected to the tuning control electrode of the phase shifter and the electrically tunable filter feedback component. Therefore, the controller in the embodiment of the present application can adjust the tuning control electrode voltage of the phase shifter and the electrically tunable filter feedback structure through a proportional integral differential control method based on Kalman filtering or other closed-loop control methods, and the lasing frequency control and frequency stabilization operation are realized based on external cavity electrical phase modulation.

[0063] Therefore, the electrically phase-tuned, narrow-linewidth, and highly frequency-stable integrated external cavity laser implemented in the embodiment of the present application not only has a small structural size, but also has low power loss and Allan variance.

[0064] The following application will further illustrate the electrically phase-tuned narrow-linewidth and highly frequency-stable integrated external cavity laser proposed in this application through specific embodiments and drawings.

[0065] Figure 2 Schematic diagram of the structure of an electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser with an all-pass filtering micro-ring.

[0066] like Figure 2 As shown, the electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser in this specific embodiment is composed of a gain chip 101, a mode spot size transformation structure 102, a phase shifter 200, a 2×2 waveguide coupler 600, an all-pass filter microring 301, an uplink and downlink feedback microring 302, an atomic frequency discrimination system 400, and a controller 500, which are interconnected or integrated on a chip.

[0067] Depend on Figure 2 It can be seen that the output end of the gain chip 101 is connected to the input end of the mode spot size conversion structure 102, the output end of the mode spot size conversion structure 102 is connected to the input end of the phase shifter 200, the output end of the phase shifter 200 is connected to the first left port of the 2×2 waveguide coupler 600, and an electrically adjustable filter feedback component is provided between the first and second right ports of the 2×2 waveguide coupler 600. The electrically tunable filter feedback component of the embodiment of the present application includes an all-pass filter microring 301 and an uplink / downlink feedback microring 302. The first and second right-side ports of the 2×2 waveguide coupler 600 are respectively connected to the input end of the all-pass filter microring 301 and the downlink end of the uplink / downlink feedback microring 302, and the output end of the all-pass filter microring 301 is connected to the uplink / downlink feedback microring 302. The output light is emitted along the second left-side port of the 2×2 waveguide coupler 600 and connected to the atomic frequency discrimination system 400. The electrical signal output end of the atomic frequency discrimination system 400 is connected to the controller 500. The output end of the controller is connected to the tuning control electrodes of the phase shifter 200, the all-pass filter microring 301 and the uplink / downlink feedback microring 302. The phase shifter 200, the 2×2 waveguide coupler 600, the all-pass filter microring 301, and the uplink / downlink feedback microring 302 are composed of a ridge waveguide structure based on a thin-film lithium niobate platform.

[0068] Furthermore, the diameter of the all-pass filter microring is no more than half the diameter of the uplink and downlink feedback microring. The free spectral range of the all-pass filter microring is more than twice that of the uplink and downlink feedback microring. Furthermore, under the same process conditions, the low-radius microring has a lower quality factor, resulting in a larger spectral half-width (FWHM). The all-pass filter microring provides side-mode suppression for the downlink spectrum of the uplink and downlink feedback microring. Due to its large FWHM, it can provide over 3dB of side-mode suppression without requiring perfect alignment with the resonant wavelength, improving alignment tolerance.

[0069] Among them, the phase shifter, all-pass filter microring, and uplink and downlink feedback microring are accompanied by tuning electrodes. The electrodes are prepared on both sides of the ridge waveguide through a sputtering process to generate an electric field perpendicular to the waveguide direction, and tuning is performed using the electro-optical effect of lithium niobate material.

[0070] like Figure 2 As shown, this specific embodiment adjusts the electrode DC bias of the uplink and downlink feedback microrings to align the resonant wavelength with the atomic clock transition spectrum, and adjusts the electrode DC bias of the all-pass filter microrings to enable single-mode lasing of the laser.

[0071] The 2×2 waveguide coupler is a lithium niobate ridge waveguide directional coupler with a power splitting ratio close to 50:50. The two split beams through the directional coupler are reversely coupled through the all-pass filtering microring and the uplink and downlink feedback microring, and then fed back to the gain chip 101 through the coupler and output to the frequency stabilization system. In this process, both split beams undergo three waveguide couplings and experience the same narrow-bandpass filtering effect, such as Figure 3 shown.

[0072] Further, Figure 2 The gain chip 101 has a laser wavelength in the 0.4-5μm band, one end is coated with a high reflectivity film (reflectivity ≥ 90%), and the other end is coated with a low reflectivity film (reflectivity ≤ 0.1%). The structure is a ridge waveguide refractive index guided type, and has an output light inclination angle in the range of 0° to 10° relative to the horizontal direction.

[0073] Figure 4 Schematic diagram of the structure of an electrically phase-modulated narrow-linewidth, high-frequency-stable integrated external cavity laser without an all-pass filtering micro-ring.

[0074] like Figure 4 As shown, the electrically phase-tuned, narrow-linewidth, and highly frequency-stable integrated external cavity laser of this embodiment comprises a gain chip 101, a mode spot size conversion structure 102, a phase shifter 200, a 2×2 waveguide coupler 600, an uplink / downlink feedback microring 302, an atomic frequency discrimination system 400, and a controller 500, all interconnected or integrated on-chip. The electrically phase-tuned filter feedback assembly 300 of this embodiment includes an uplink / downlink feedback microring 302. The first and second right-side ports of the 2×2 waveguide coupler 600 are connected to the uplink and downlink feedback microring 302, respectively.

[0075] It should be noted that Figure 4 The gain spectrum half-width of the gain chip in the circuit is no more than four times the free spectral range of the uplink and downlink feedback microring to ensure sufficient side mode suppression, and the embodiments of the present application align the resonant wavelength with the atomic clock transition spectrum line by adjusting the electrode DC bias of the uplink and downlink feedback microring.

[0076] The substructures and substructure characteristics of the remaining components are the same as those of the above-mentioned electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser with an all-pass filtering microring, and will not be described in detail here.

[0077] Based on the above implementation, the linewidth narrowing principle and the electrically phase-modulated frequency stabilization scheme of the electrically phase-modulated narrow-linewidth high-frequency-stable integrated external cavity laser without an all-pass filter micro-ring are as follows:

[0078] like Figure 4 As shown, laser light emitted by the gain chip is coupled into an on-chip ridge waveguide within a thin-film lithium niobate external cavity via a spot size conversion structure. The light then propagates along the ridge waveguide, passing through an on-chip phase shifter, a 2×2 waveguide coupler, and an electrically tunable filter feedback structure to produce a filtered narrow-spectrum optical signal. This signal then passes through the 2×2 waveguide coupler again, splitting it into two paths: one feeding back to the gain chip and the other output to the frequency stabilization system. The narrow-spectrum signal is fed back into the gain chip cavity, where it forms a laser resonant cavity with the high-reflectivity coating. Its narrow spectrum narrows the laser beam width. The output optical signal enters the atomic frequency discrimination system, ultimately outputting a frequency discrimination electrical signal. Benefiting from the increased output power brought about by the low coupling factor on the external cavity chip, the frequency discrimination signal power and signal-to-noise ratio are also improved. The frequency discrimination signal guides the controller to fine-tune the tuning electrodes of the phase shifter and the electrically tunable filter feedback component based on the DC bias, stabilizing the output optical frequency to the atomic clock transition frequency. The frequency deviation caused by the controller adjusting the electrode voltage based on the electro-optical effect will be quickly reflected in the frequency discrimination signal. Therefore, closed-loop control methods such as the proportional-integral-differential method based on Kalman filtering can be used to achieve frequency stabilization.

[0079] According to the electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser proposed in the embodiment of the present application, the output light of the gain chip is connected to the phase shifter through a mode spot size conversion structure. The output end of the phase shifter is connected to a left port of a 2×2 waveguide coupler. An electrically tunable filter feedback component is set between the two right ports of the 2×2 waveguide coupler. The second left port serves as the laser output port and is connected to an atomic frequency discrimination system that generates a frequency discrimination signal. The frequency discrimination signal is output to the control circuit. The controller adjusts the tuning electrode voltage of the phase shifter and the filter feedback structure on the external cavity chip based on the electro-optical effect to achieve frequency stabilization. The embodiment of the present application achieves narrow-linewidth, high-frequency-stable lasing through a low-power-loss filter feedback external cavity structure and the application of high-speed electrical phase tuning in the frequency stabilization system. In addition, the embodiment of the present application utilizes the fast electro-optical tuning of the thin-film lithium niobate external cavity and the external cavity design with low power loss and high alignment tolerance to effectively improve the integration and reduce the Allan variance.

[0080] Next, a frequency stabilization method for an electrically phase-adjustable, narrow-linewidth, and highly frequency-stable integrated external cavity laser according to an embodiment of the present application will be described with reference to the accompanying drawings.

[0081] Figure 5This is a flow chart of a frequency stabilization method for an electrically phase-modulated, narrow-linewidth, and highly frequency-stable integrated external cavity laser provided in an embodiment of the present application.

[0082] like Figure 5 As shown, the frequency stabilization method of the electrically phase-modulated narrow-linewidth high-frequency-stable integrated external cavity laser includes the following steps:

[0083] In step S501 , a first laser signal is generated.

[0084] Optionally, in one embodiment of the present application, generating the first laser signal includes: generating the first laser signal based on a gain chip; and transmitting the first laser signal according to a preset loss rate through a mode spot size transformation structure.

[0085] In step S502 , under a preset condition, the first laser signal is phase-shifted to obtain a second laser signal.

[0086] In step S503, the second laser signal is filtered to obtain a narrow-spectrum optical signal, and under a preset condition, the first laser signal is electrically tuned, and a frequency discrimination signal is generated based on the narrow-spectrum optical signal.

[0087] In step S504, based on the frequency discrimination signal, the tuning electrode voltages of the phase shifter and the electrically tunable filter feedback structure are adjusted according to a preset control strategy to change the laser signal frequency until the laser signal reaches a preset frequency stabilization condition.

[0088] Optionally, in one embodiment of the present application, the phase shifter and the electrically tunable filter feedback component are composed of a straight waveguide and a curved waveguide prepared on a thin-film lithium niobate platform based on a lithium niobate thin film substrate.

[0089] Optionally, in one embodiment of the present application, it further includes: using a waveguide coupler to transmit the optical signal between the gain chip and the electrically tunable filter feedback component, and transmitting the narrow spectrum optical signal to the atomic frequency discrimination system.

[0090] It should be noted that the aforementioned explanation of the embodiment of the electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser device is also applicable to the frequency stabilization method of the electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser of this embodiment, and will not be repeated here.

[0091] According to the frequency stabilization method of an electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser proposed in an embodiment of the present application, a first laser signal is generated; under preset conditions, the first laser signal is phase-shifted to obtain a second laser signal; the second laser signal is filtered to obtain a narrow-spectrum optical signal, and under preset conditions, the first laser signal is electrically tuned, and a frequency discrimination signal is generated based on the narrow-spectrum optical signal; based on the frequency discrimination signal, the tuning electrode voltages of the phase shifter and the electrically tunable filter feedback structure are adjusted according to a preset control strategy to change the frequency of the first laser signal until the first laser signal reaches a preset frequency stabilization condition, thereby combining the optimized electrically tunable filter feedback external cavity into the frequency discrimination and frequency stabilization system, and utilizing a low-power-loss, high-speed electro-optically tuned thin-film lithium niobate external cavity to realize a small-sized electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser.

[0092] Figure 6 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. The electronic device may include:

[0093] A memory 601 , a processor 602 , and a computer program stored in the memory 601 and executable on the processor 602 .

[0094] When the processor 602 executes the program, the frequency stabilization method of the electrically phase-modulated narrow-linewidth and highly frequency-stable integrated external cavity laser provided in the above embodiment is implemented.

[0095] Furthermore, the electronic device further includes:

[0096] The communication interface 603 is used for communication between the memory 601 and the processor 602 .

[0097] The memory 601 is used to store computer programs that can be run on the processor 602 .

[0098] The memory 601 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0099] If the memory 601, processor 602, and communication interface 603 are implemented independently, the communication interface 603, memory 601, and processor 602 can be connected to each other via a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 6 Only one thick line is used in the diagram, but this does not mean that there is only one bus or one type of bus.

[0100] Optionally, in a specific implementation, if the memory 601, the processor 602 and the communication interface 603 are integrated on a chip, the memory 601, the processor 602 and the communication interface 603 can communicate with each other through an internal interface.

[0101] The processor 602 may be a central processing unit (CPU), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0102] An embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the frequency stabilization method for the electrically phase-adjusted narrow-linewidth, high-frequency-stable integrated external cavity laser as described above.

[0103] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" 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 application. 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 can be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0104] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this application, "N" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0105] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing a custom logical function or process step, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may be performed in a different order than shown or discussed, including performing functions in a substantially simultaneous manner or in a reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present application pertain.

[0106] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection with one or N wires (electronic devices), a portable computer disk cartridge (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and programmable read-only memory (EPROM or flash memory), fiber optic devices, and a portable compact disc read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program can be obtained electronically by optically scanning the paper or other medium and then editing, interpreting or processing it in other suitable ways as necessary, and then storing it in a computer memory.

[0107] It should be understood that various parts of the present application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiment, the N steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0108] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0109] In addition, the functional units in the various embodiments of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into a module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0110] The storage medium mentioned above may be a read-only memory, a magnetic disk, or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application. Persons skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. An electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser, characterized in that: include: An input component for generating a first laser signal; a phase shifter, configured to receive the first laser signal transmitted by the input component and, under a preset condition, phase-shift the first laser signal to obtain a second laser signal; an electrically tunable filter feedback component, configured to receive a second laser signal transmitted by the phase shifter, filter the second laser signal, and feed the second laser signal back to the input component to obtain a narrow-spectrum optical signal, and electrically tune the first laser signal under the preset conditions; an atomic frequency discrimination system, configured to receive the narrow spectrum optical signal output by the electrically tunable filter feedback component, generate a frequency discrimination signal, and The controller is configured to adjust the tuning electrode voltages of the phase shifter and the electrically tunable filter feedback component based on the frequency discrimination signal and according to a preset control strategy, thereby changing the frequency of the first laser signal until the first laser signal reaches a preset frequency stabilization condition.

2. The electrically phase-tuned, narrow-linewidth, and highly frequency-stable integrated external cavity laser according to claim 1, characterized in that: The phase shifter and the electrically tunable filter feedback component are composed of a straight waveguide and a curved waveguide prepared on a thin-film lithium niobate platform based on a lithium niobate thin film substrate.

3. The electrically phase-tuned, narrow-linewidth, and highly frequency-stable integrated external cavity laser according to claim 1, characterized in that: The input component includes: a gain chip, configured to generate the first laser signal; The mode spot size transformation structure is used to transmit the first laser signal according to a preset loss rate.

4. The electrically phase-tuned, narrow-linewidth, and highly frequency-stable integrated external cavity laser according to claim 3, characterized in that: Also includes: A waveguide coupler is used to transmit the optical signal between the gain chip and the electrically tunable filter feedback component, and transmit the narrow-spectrum optical signal to the atomic frequency discrimination system.

5. A frequency stabilization method for an electrically phase-tuned, narrow-linewidth, high-frequency-stable integrated external cavity laser, characterized in that: The electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser according to any one of claims 1 to 4 is used, wherein the method comprises the following steps: generating the first laser signal; Under the preset conditions, phase-shifting the first laser signal to obtain the second laser signal; filtering the second laser signal to obtain a narrow-spectrum optical signal, electrically tuning the first laser signal under the preset condition, and generating a frequency discrimination signal based on the narrow-spectrum optical signal; and Based on the frequency discrimination signal, the tuning electrode voltages of the phase shifter and the electrically tunable filter feedback component are adjusted according to the preset control strategy to change the frequency of the first laser signal until the first laser signal reaches the preset frequency stabilization condition.

6. The frequency stabilization method of the electrically phase-modulated narrow-linewidth high-frequency-stable integrated external cavity laser according to claim 5, characterized in that: The phase shifter and the electrically tunable filter feedback component are composed of a straight waveguide and a curved waveguide prepared on a thin-film lithium niobate platform based on a lithium niobate thin film substrate.

7. The frequency stabilization method of the electrically phase-modulated narrow-linewidth high-frequency-stable integrated external cavity laser according to claim 5, characterized in that: Generating the first laser signal includes: generating the first laser signal based on the gain chip; The first laser signal is transmitted through the mode spot size transformation structure according to a preset loss rate.

8. The frequency stabilization method of the electrically phase-modulated narrow-linewidth high-frequency-stable integrated external cavity laser according to claim 5, characterized in that: Also includes: The waveguide coupler is used to transmit the optical signal between the gain chip and the electrically tunable filter feedback component, and the narrow-spectrum optical signal is transmitted to the atomic frequency discrimination system.

9. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the frequency stabilization method for the electrically phase-tuned narrow-linewidth, high-frequency-stable integrated external cavity laser according to any one of claims 1 to 4.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is executed by a processor to implement the frequency stabilization method of the electrically phase-modulated narrow-linewidth and highly frequency-stable integrated external cavity laser according to any one of claims 1 to 4.

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