Chip optical clock based on modulation transfer spectrum principle and implementation method thereof

Abstract

The application relates to the technical field of atomic clocks, and provides a chip optical clock based on a modulation transfer spectrum principle and an implementation method thereof. The chip optical clock comprises: an on-chip narrow-line-width laser for emitting laser; a waveguide beam splitter for splitting the laser into two beams; one beam of laser is used for inputting into an electro-optic phase modulator, and the other beam of laser is used for inputting into a MEMS atomic cell; the electro-optic phase modulator is used for phase-modulating the one beam of laser and outputting pump light; the MEMS atomic cell is used for modulating and transferring the other beam of laser based on the pump light to obtain a probe spectrum; a photoelectric detector is used for converting the detected probe spectrum into an electric signal; a high-speed servo feedback control integrated circuit is used for converting the received electric signal into a feedback control signal, inputting the feedback control signal into a feedback control port of the on-chip narrow-line-width laser, realizing full-bandwidth locking, and outputting an optical clock signal. The above-designed chip optical clock has small integration difficulty and is easy to realize full-chip optical clock.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of atomic clock, and particularly to a chip optical clock based on modulation transfer spectrum principle and an implementation method thereof. BACKGROUND

[0002] The atomic clock is the highest precision time frequency signal standard equipment or instrument at present, and is widely applied to technical fields such as positioning, navigation, reconnaissance and communication, and plays an important role in basic research and practical application. The optical frequency atomic clock is an atomic clock whose atomic energy level transition frequency is in the optical frequency band, and is also called optical clock. However, the traditional optical clock is too large in volume, complex in system, high in cost, and difficult to be integrated, miniaturized or even chipped, which greatly limits its application scenarios. Therefore, developing high-performance miniaturized optical clock has been a hotspot in various fields.

[0003] In the prior art, based on a two-photon system, a miniaturized optical clock with a volume of 35 mL and a power consumption of 450 mW is completed. The stability index of the optical clock reaches 2.9E-12.

[0004] However, the two-photon system in the above-mentioned miniaturized optical clock needs a complex fluorescence collection device, which is difficult to integrate and is not easy to realize the full-chip of the optical clock. SUMMARY

[0005] The present application provides a chip optical clock based on modulation transfer spectrum principle and an implementation method thereof, which is used to solve the problem of large integration difficulty and difficulty in realizing full-chip of the existing miniaturized optical clock.

[0006] In a first aspect, the present application provides a chip optical clock based on modulation transfer spectrum principle, which comprises: an on-chip narrow linewidth laser, a waveguide beam splitter, a micro-electro-mechanical system (MEMS) atomic cell, an electro-optic phase modulator, a photoelectric detector and a high-speed servo feedback control integrated circuit.

[0007] The output end of the on-chip narrow linewidth laser is connected with the input end of the waveguide beam splitter, and the on-chip narrow linewidth laser is used for emitting laser.

[0008] The waveguide beam splitter is used for dividing the laser into two beams. One beam of laser is used for inputting into the electro-optic phase modulator, and the other beam of laser is used for inputting into the MEMS atomic cell.

[0009] The electro-optic phase modulator is used for phase modulating the input one beam of laser, and outputs pump light.

[0010] The MEMS atomic cell is used for realizing modulation transfer of the other beam of laser based on the pump light, and obtaining a probe spectrum.

[0011] The photoelectric detector is used for detecting the detection spectrum and converting the detection spectrum into an electrical signal;

[0012] One end of the high-speed servo feedback control integrated circuit is connected with an output end of the photoelectric detector, and is used for converting the electrical signal output by the photoelectric detector into a feedback control signal;

[0013] The other end of the high-speed servo feedback control integrated circuit is connected with a feedback control port of the on-chip narrow linewidth laser, and the feedback control port is used for receiving the feedback control signal and realizing full-bandwidth locking of the feedback control signal, and outputting an optical clock signal.

[0014] Optionally, the high-speed servo feedback control integrated circuit comprises a signal amplifier, a signal generator, a frequency mixer and a high-speed servo feedback control circuit.

[0015] An input end of the signal amplifier is connected with an output end of the photoelectric detector, and the signal amplifier is used for amplifying the electrical signal to obtain an amplified signal.

[0016] An output end of the signal amplifier is connected with one input end of the frequency mixer, and one output end of the signal generator is connected with the other input end of the frequency mixer, and the signal generator is used for providing a demodulation signal to the frequency mixer.

[0017] The frequency mixer is used for receiving the amplified signal and the demodulation signal, and performing frequency mixing on the amplified signal and the demodulation signal to obtain a modulation transfer spectrum signal.

[0018] An output end of the frequency mixer is connected with the high-speed servo feedback control circuit, and the high-speed servo feedback control circuit is used for processing the modulation transfer spectrum signal to obtain a feedback control signal.

[0019] Optionally, the waveguide beam splitter is specifically used for splitting the laser into two beams with different light intensities, and a laser beam with a relatively high light intensity is used as a pump laser, and a laser beam with a relatively low light intensity is used as a detection laser.

[0020] The other output end of the signal generator is connected with the electro-optical phase modulator, and the signal generator is further used for providing a driving radio frequency signal to the electro-optical phase modulator.

[0021] The electro-optical phase modulator is specifically used for performing phase modulation on the pump laser based on the driving radio frequency signal, and outputting a pump light.

[0022] The MEMS atomic gas cell is specifically used for realizing reverse superposition of the pump light and the detection laser, and interacting with a quantum reference medium in the MEMS atomic gas cell to obtain a detection spectrum.

[0023] Optionally, the quantum reference medium in the MEMS atomic cell comprises rubidium atoms or cesium atoms.

[0024] Optionally, the on-chip narrow-linewidth laser is a micro-ring external cavity laser.

[0025] Optionally, the electro-optical phase modulator is a waveguide-level lithium niobate thin-film electro-optical phase modulator.

[0026] Optionally, the MEMS atomic cell is externally provided with a magnetic shield and a temperature control device for reducing the influence of external magnetic field and temperature.

[0027] In a second aspect, the application further provides an implementation method of a chip optical clock based on the modulation transfer spectrum principle, applied to a chip optical clock comprising an on-chip narrow-linewidth laser, a waveguide beam splitter, a micro-electro-mechanical system (MEMS) atomic cell, an electro-optical phase modulator, a photoelectric detector, and a high-speed servo feedback control integrated circuit; the method comprises:

[0028] The on-chip narrow-linewidth laser emits laser light, which is split into two beams after passing through the waveguide beam splitter: one beam of laser light is input to the electro-optical phase modulator, and the other beam of laser light is input to the MEMS atomic cell.

[0029] The electro-optical phase modulator performs phase modulation on the input one beam of laser light, and outputs pump light.

[0030] The MEMS atomic cell realizes modulation transfer on the other beam of laser light based on the pump light, and obtains a probe spectrum.

[0031] The photoelectric detector detects the probe spectrum and converts the probe spectrum into an electrical signal.

[0032] The high-speed servo feedback control integrated circuit converts the electrical signal output by the photoelectric detector into a feedback control signal.

[0033] The feedback control port of the on-chip narrow-linewidth laser receives the feedback control signal and realizes full-bandwidth locking of the feedback control signal, and outputs an optical clock signal.

[0034] Optionally, the electro-optical phase modulator performs phase modulation on the input one beam of laser light, and outputs pump light, comprising:

[0035] The electro-optical phase modulator determines a transition energy level in response to a modulation operation.

[0036] The electro-optical phase modulator adjusts the phase of the input laser beam based on the transition energy level, determines the phase modulation depth, and modulates the laser beam based on the phase modulation depth to output pump light.

[0037] Optionally, the feedback control port includes a high-speed feedback control port and a slow-speed feedback control port; the high-speed feedback control port is used for stabilizing a high-frequency feedback control signal, and the slow-speed feedback control port is used for stabilizing a low-frequency feedback control signal.

[0038] In summary, the application provides a chip optical clock based on the modulation transfer spectrum principle and an implementation method thereof. Laser light can be emitted by an on-chip narrow-linewidth laser in the chip optical clock to a waveguide beam splitter in the chip optical clock, so that the waveguide beam splitter divides the laser light into two beams. One beam of laser light is used for input to an electro-optical phase modulator in the chip optical clock, and the other beam of laser light is used for input to a MEMS atomic cell in the chip optical clock. The electro-optical phase modulator modulates the input laser light in phase to output pump light, and the MEMS atomic cell modulates the other beam of laser light based on the pump light, thereby obtaining a probe spectrum. Further, a photodetector in the chip optical clock can detect the probe spectrum and convert the probe spectrum into an electrical signal. Further, the electrical signal is output to a high-speed servo feedback control integrated circuit, so that the high-speed servo feedback control integrated circuit converts the received electrical signal into a feedback control signal. Further, the high-speed servo feedback control integrated circuit outputs the feedback control signal to a feedback control port of the on-chip narrow-linewidth laser, for realizing full-bandwidth locking of the feedback control signal, and outputs an optical clock signal. Through the above-designed chip optical clock, the on-chip laser and the electro-optical phase modulator are used to realize high-chipization of the optical clock, so that the integration difficulty is reduced. Based on the modulation transfer spectrum principle, the laser frequency of the optical clock is locked to the energy level of the atom, thereby realizing a chip optical clock with high stability. BRIEF DESCRIPTION OF DRAWINGS

[0039] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one embodiment consistent with the present application and, together with the description, serve to explain the principles of the application.

[0040] Figure 1 An application scenario diagram is provided for the embodiment of the application;

[0041] Figure 2 A structure diagram of a chip optical clock based on the modulation transfer spectrum principle is provided for the embodiment of the application;

[0042] Figure 3 An on-chip structure diagram of a chip optical clock based on the modulation transfer spectrum principle is provided for the embodiment of the application;

[0043] Figure 4A specific structure schematic diagram of a chip optical clock based on the principle of modulation transfer spectrum provided by the embodiment of the present application;

[0044] Figure 5 A flowchart of an implementation method of a chip optical clock based on the principle of modulation transfer spectrum provided by the embodiment of the present application.

[0045] The specific embodiments of the present application have been shown in the above-described drawings, and will be described in more detail hereinafter. These drawings and the written description are not intended to restrict the scope of the present application concept in any way, but to illustrate the present application concept to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0046] In order to clearly describe the technical solutions of the embodiments of the present application, in the embodiments of the present application, the same items or similar items with basically the same functions and effects are distinguished by using "first", "second", etc. For example, the first device and the second device are only used to distinguish different devices, and do not limit the order. Those skilled in the art can understand that "first", "second", etc. do not limit the number and execution order, and "first", "second", etc. also do not necessarily mean different.

[0047] It should be noted that in the present application, "exemplary" or "for example" is used to represent an example, illustration or description. Any embodiment or design scheme described as "exemplary" or "for example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the use of "exemplary" or "for example" is intended to present the relevant concept in a specific manner.

[0048] In the present application, "at least one" means one or more, and "multiple" means two or more. "And / or" describes the association between the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the following cases: A exists alone, A and B exist together, and B exists alone, where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects. "At least one of the following" or similar expressions means any combination of these items, including any combination of single item or multiple items. For example, at least one of a, b, or c, can represent a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0049] Atomic clock is the highest precision time frequency standard standard device at present, which is applied to advanced technical fields such as positioning, navigation, reconnaissance, communication and plays an important role in basic research and practical application. Optical frequency atomic clock, also known as optical clock, uses narrow linewidth laser to interact with atoms to obtain high signal-to-noise ratio frequency discrimination signal, so as to lock the laser frequency to obtain the output of standard frequency.

[0050] The frequency accuracy and stability indexes of the best optical clock at present have entered the 1E-18 level. In theory, the optical clock index is very potential if it is 5 orders of magnitude higher than that of microwave clock. However, the best optical clock index has reached 2 orders of magnitude higher than that of the best microwave clock, so that the research of optical clock has deviated from the principle exploration stage and turned to the system parameter optimization and the practicalization of the whole clock system.

[0051] One development trend of atomic clock is that optical clock replaces microwave clock. However, the traditional optical clock is too large in volume, complex in system, high in cost and difficult to integrate, miniaturize and even chip, which greatly limits its application scenarios. Many major projects put forward higher requirements for the miniaturization of atomic clock while pursuing higher accuracy and stability.

[0052] Therefore, the development of high-performance miniaturized optical clock can greatly improve the ability of precise measurement and application field of time frequency. How to realize chip optical clock has been a hot spot in various fields, especially how to reduce the volume and power consumption of optical clock as much as possible under the condition of ensuring high index and realizing on-chip integration is a big difficulty.

[0053] In one possible implementation, based on a two-photon system, a miniaturized optical clock with a volume of 35mL and a power consumption of 450mW is completed. The stability index of the optical clock reaches 2.9E-12.

[0054] However, the two-photon system in the above-mentioned miniaturized optical clock needs a complex fluorescence collection device, which is difficult to integrate and not easy to realize the full-chip of optical clock.

[0055] In view of the above problems, the present application provides a chip optical clock based on modulation transfer spectrum principle. The highly chip optical clock is realized by using on-chip narrow linewidth laser and electro-optic phase modulator, and the laser frequency is locked on the hyperfine energy level of the atom based on the micro-electro-mechanical system (MEMS) atomic cell by using the modulation transfer spectrum technology with nonlinear four-wave mixing effect, so as to realize the chip optical clock based on modulation transfer spectrum. The chip optical clock has high stability, not only reduces the difficulty of chip integration, but also greatly reduces the volume of optical clock. In this way, the application scenarios and application environments of atomic clock can be expanded, and a wider space is provided for the development of atomic clock.

[0056] It should be noted that the modulation transfer spectrum technology is a heterodyne spectrum technology, which has the advantages of no Doppler background, high signal-to-noise ratio, high resolution, high sensitivity and the like. Specifically, the modulation transfer spectrum technology effectively eliminates the influence of noise irrelevant to the laser frequency by using a heterodyne detection manner, and the detection sensitivity can reach the shot noise limit.

[0057] Exemplarily, Figure 1 An application scenario schematic diagram provided for an embodiment of the present application, a chip optical clock based on the modulation transfer spectrum principle provided by the present application can be applied to, for example, Figure 1 as shown in the application scenario. The application scenario includes a man-made satellite 1011, a man-made satellite 1012, a man-made satellite 1013, a base station 102 and a global positioning system (GPS) receiver 103, wherein each man-made satellite is equipped with a group of chip optical clocks 1041, and correspondingly, the base station 102 is also equipped with a group of chip optical clocks 1042.

[0058] Specifically, the GPS receiver 103 receives time signals sent by the chip optical clocks 1041 in the man-made satellites 1011, 1012 and 1013 and time signals sent by the chip optical clocks 1041 in the base station 102, and further, determines the relative time delay of the four time signal sources, and then converts them into three absolute spatial coordinates and one absolute time coordinate, so that the GPS receiver 103 can grasp the real-time position.

[0059] It can be understood that in a three-dimensional space, a coordinate system is established, and when the coordinates of three points and the distances between the fourth unknown point and the known points are known, the coordinates of the unknown point can be determined, wherein the chip optical clocks in each man-made satellite and the base station send ephemeris together when sending time signals, so that the time information and the distance can be obtained at the same time in the process of calculating the position of the man-made satellite.

[0060] The technical solutions of the present application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of the present application will be described below with reference to the drawings.

[0061] Exemplarily, the present application provides a chip optical clock based on the modulation transfer spectrum principle, Figure 2 A structure schematic diagram of a chip optical clock based on the modulation transfer spectrum principle provided for an embodiment of the present application is shown in FIG. 2, wherein the chip optical clock includes an on-chip narrow linewidth laser, a waveguide beam splitter, a micro-electro-mechanical system (MEMS) atomic cell, an electro-optic phase modulator, a photoelectric detector and a high-speed servo feedback control integrated circuit. Figure 2 ​

[0062] The output end of the on-chip narrow linewidth laser is connected with the input end of the waveguide beam splitter, and the on-chip narrow linewidth laser is used for emitting laser;

[0063] The waveguide beam splitter is used for splitting the laser into two beams; one beam of laser is used for inputting into the electro-optical phase modulator, and the other beam of laser is used for inputting into the MEMS atomic cell;

[0064] The electro-optical phase modulator is used for phase modulating the inputted one beam of laser, and outputting pump light;

[0065] The MEMS atomic cell is used for realizing modulation transfer of the other beam of laser based on the pump light, and obtaining probe spectrum;

[0066] The photoelectric detector is used for detecting the probe spectrum, and converting the probe spectrum into an electrical signal;

[0067] One end of the high-speed servo feedback control integrated circuit is connected with the output end of the photoelectric detector, and is used for converting the electrical signal outputted by the photoelectric detector into a feedback control signal;

[0068] The other end of the high-speed servo feedback control integrated circuit is connected with a feedback control port of the on-chip narrow linewidth laser, the feedback control port is used for receiving the feedback control signal, and realizing full-bandwidth locking of the feedback control signal, and outputting an optical clock signal.

[0069] For example, the on-chip narrow linewidth laser can emit laser of 780.246 nm, which is split into two beams after the waveguide beam splitter, one beam as pump laser and the other beam as probe laser. Further, the pump laser is inputted into the electro-optical phase modulator, and the phase modulation is realized by the electro-optical phase modulator, and the output pump light is the laser signal outputted by the electro-optical phase modulator after being modulated by a modulation frequency, for example, the electro-optical phase modulator can be phase modulated by a modulation frequency of 10 MHz, and the specific value of the modulation frequency is not limited in the embodiment of the application, which is related to the energy level corresponding to the root clock transition, that is, after the transition energy level is determined, the corresponding modulation frequency is determined, for example, the transition energy level 5S 1 / 2 F=2→5P 3 / 2 F’=3 corresponds to a natural linewidth of about 6 MHz, and the corresponding modulation frequency is 10 MHz, wherein S and P represent different transition orbits.

[0070] Further, the pump light and the probe light are incident on the MEMS atomic cell from opposite directions, are overlapped in the MEMS atomic cell, and the modulation signal is transferred from the pump light to the probe spectrum through the degenerate four-wave mixing process, so as to obtain the probe spectrum.

[0071] Further, the photoelectric detector can detect the probe spectrum from the MEMS atomic cell and convert the probe spectrum into an electrical signal. Further, the photoelectric detector can input the electrical signal into a high-speed servo feedback control integrated circuit. After the high-speed servo feedback control integrated circuit processes the electrical signal through signal amplification, frequency mixing, servo feedback, and the like, a feedback control signal is obtained. Then, the high-speed servo feedback control integrated circuit inputs the feedback control signal to a feedback control port of the on-chip narrow-linewidth laser, completes full-bandwidth locking of the on-chip narrow-linewidth laser, that is, full-bandwidth locking of the feedback control signal, and outputs an optical clock signal, that is, a required high-stability laser.

[0072] It should be noted that the wavelength corresponding to the laser emitted by the on-chip narrow-linewidth laser in the embodiments of the present application is not specifically limited, which can be the wavelength described in the above embodiments, or can be other wavelengths, such as 532 nm laser.

[0073] Exemplarily, Figure 3 A schematic diagram of an on-chip structure of a chip optical clock based on the modulation transfer spectrum principle is provided in the embodiments of the present application, as shown in the figure, the chip optical clock includes: an on-chip narrow-linewidth laser 301, a waveguide beam splitter 302, a MEMS atomic cell 303, an electro-optic phase modulator 304, and a photoelectric detector 305. The above structure has a substrate and can be integrated on a chip, while a high-speed servo feedback control integrated circuit is integrated on a chip circuit (not shown in the figure). Figure 3 Therefore, the chip optical clock based on the modulation transfer spectrum principle provided in the present application applies modulation transfer spectrum frequency stabilization technology and full-bandwidth high-speed servo feedback mechanism to stabilize the laser frequency of the chip optical clock on the hyperfine spectral line of an atom, so as to realize a high-stability atomic optical frequency standard. While ensuring the stability of the optical frequency standard, the key devices in the waveguide transmission and the chip system are used, such as chipization of the waveguide beam splitter, the MEMS atomic cell, the photoelectric detector, the electro-optic phase modulator, and the like. The chipization of the optical frequency standard and the integration of the frequency locking components of the atomic precise spectrum are realized under the condition of high stability, the integration difficulty is reduced, and the high-stability chip optical clock based on the modulation transfer spectrum is realized.

[0074] It can be understood that the design of the above chip optical clock based on the modulation transfer spectrum principle has certain significant value in promoting the rapid development of the optical clock field, and in original innovation, promoting core devices and key applications to be self-controllable.

[0075] Optionally, the high-speed servo feedback control integrated circuit includes: a signal amplifier, a signal generator, a frequency mixer, and a high-speed servo feedback control circuit.

[0076]

[0077] ​The input end of the signal amplifier is connected with the output end of the photoelectric detector, and the signal amplifier is used for amplifying the electric signal to obtain an amplified signal.

[0078] The output end of the signal amplifier is connected with one input end of the frequency mixer, and one output end of the signal generator is connected with the other input end of the frequency mixer, and the signal generator is used for providing a demodulation signal to the frequency mixer.

[0079] The frequency mixer is used for receiving the amplified signal and the demodulation signal, and performing frequency mixing on the amplified signal and the demodulation signal to obtain a modulation transfer spectrum signal.

[0080] The output end of the frequency mixer is connected with the high-speed servo feedback control circuit, and the high-speed servo feedback control circuit is used for processing the modulation transfer spectrum signal to obtain a feedback control signal.

[0081] In the embodiment of the application, the signal generator can refer to a radio frequency device capable of providing various frequency, waveform and output level electric signals, and the frequency mixing can refer to a process of changing a signal from one frequency to another frequency, which is actually a process of linearly moving a frequency spectrum, and is used for stabilizing a signal.

[0082] Exemplarily, Figure 4 A specific structure schematic diagram of a chip optical clock based on the modulation transfer spectrum principle is provided in the embodiment of the application, as shown in Figure 4 The chip optical clock includes an on-chip narrow linewidth laser 301, a waveguide beam splitter 302, a MEMS atomic cell 303, an electro-optic phase modulator 304, a photoelectric detector 305 and a high-speed servo feedback control integrated circuit, and the high-speed servo feedback control integrated circuit includes a signal amplifier 401, a signal generator 402, a frequency mixer 403 and a high-speed servo feedback control circuit 404.

[0083] Specifically, the electric signal obtained by the photoelectric detector 305 is input to the signal amplifier 401, and the amplified signal is obtained after the electric signal is amplified by the signal amplifier 401, one end of the signal amplifier 401 is connected with the frequency mixer 403, therefore the signal amplifier 401 inputs the amplified signal to the frequency mixer 403, the other end of the frequency mixer 403 is connected with the signal generator 402, the signal generator 402 provides a demodulation signal to the frequency mixer 403, and the frequency mixer 403 performs frequency mixing on the amplified signal and the demodulation signal, and then the output end of the frequency mixer 403 outputs a modulation transfer spectrum signal.

[0084] Further, the modulation transfer spectrum signal obtained after the above phase-sensitive demodulation process is used as a locking required error signal and is input to the high-speed servo feedback control circuit 404 to obtain a feedback control signal, and the laser frequency is locked on the hyperfine energy level of the atom.

[0085] Therefore, the application embodiment realizes the chip optical clock based on the modulation transfer spectrum by applying the modulation transfer spectrum technology with the nonlinear four-wave mixing effect, so that the chip optical clock can obtain a signal with higher sensitivity, sufficient amplification and appropriate frequency band, and the obtained signal is more stable.

[0086] Optionally, the waveguide beam splitter is specifically used for splitting the laser into two beams with different light intensities, and a laser beam with a stronger light intensity is used as the pump laser, and a laser beam with a weaker light intensity is used as the probe laser.

[0087] Another output end of the signal generator is connected with the electro-optical phase modulator, and the signal generator is further used for providing a driving radio frequency signal to the electro-optical phase modulator.

[0088] The electro-optical phase modulator is specifically used for achieving phase modulation on the pump laser based on the driving radio frequency signal, and outputting the pump light.

[0089] The MEMS atomic cell is specifically used for achieving reverse superposition of the pump light and the probe laser, and interacting with the quantum reference medium in the MEMS atomic cell to obtain the probe spectrum.

[0090] In the application embodiment, when the electro-optical phase modulator achieves phase modulation on the pump laser, the modulation depth can be adjusted by adjusting the amplitude of the driving radio frequency signal, the laser is modulated based on the modulation depth, and the pump light is output, for example, the laser is modulated by using a phase modulation depth of about 1-2 rad, wherein the driving radio frequency signal is output to the electro-optical phase modulator by the signal generator.

[0091] Specifically, after the pump light is modulated by the driving radio frequency signal, the pump light and the probe laser collide in the MEMS atomic cell, and the modulation signal is transferred from the radio frequency modulated light beam pump light to the unmodulated light beam probe spectrum through the nonlinear medium degenerate four-wave mixing process, and the probe spectrum is obtained.

[0092] Therefore, by applying the modulation transfer spectrum technology with the nonlinear four-wave mixing effect, the application stabilizes the output frequency of the laser and locks the output frequency of the laser on the atomic fine level, thereby improving the signal-to-noise ratio and the stability of the chip optical clock.

[0093] Optionally, the quantum reference medium in the MEMS atomic cell includes rubidium atoms or cesium atoms.

[0094] In the embodiment of the present application, the MEMS atomic cell can adopt a micro-sized rubidium atom MEMS bonded atomic cell or a micro-sized cesium atom MEMS bonded atomic cell, and correspondingly, the quantum reference medium in the MEMS atomic cell can be rubidium atoms or cesium atoms.

[0095] It should be noted that the quantum reference medium is not limited to rubidium atoms or cesium atoms, but can also be lithium atoms, sodium atoms, potassium atoms, and other alkali metal atoms, as long as the same effect can be achieved, and the embodiment of the present application does not make specific limitations.

[0096] It can be understood that rubidium atoms have the advantages of low melting point, high reserves, and easy extraction, and generally heating the atomic cell to above room temperature can prepare sufficient saturated vapor pressure for realizing the chip optical clock. In addition, the rubidium atom spectrum line is simple, and for the clock transition signal, more atoms can participate in contribution, and correspondingly, cesium atoms also have similar functions, which will not be described here, and therefore, the embodiment of the present application adopts rubidium atoms or cesium atoms as the quantum reference medium, which can greatly improve the atom utilization rate.

[0097] Optionally, the on-chip narrow linewidth laser is a micro-ring external cavity laser.

[0098] In the embodiment of the present application, the on-chip narrow linewidth laser is a micro-ring external cavity laser, which adopts a lithium niobate substrate and can be integrated on-chip.

[0099] It should be noted that the embodiment of the present application can also use other types of narrow linewidth lasers, which can achieve the effect of on-chip integration, and the embodiment of the present application does not make specific limitations.

[0100] Therefore, the on-chip narrow linewidth laser with a lithium niobate substrate can reduce the integration difficulty.

[0101] Optionally, the electro-optic phase modulator is a waveguide-level lithium niobate thin film electro-optic phase modulator.

[0102] In the embodiment of the present application, the electro-optic phase modulator is a lithium niobate thin film electro-optic phase modulator, which is a waveguide-level lithium niobate thin film electro-optic phase modulator. The thin film lithium niobate electro-optic phase modulator has the advantages of low cost, small size, batch production, complementary metal oxide semiconductor (CMOS) process compatibility, and the like.

[0103] It should be noted that the embodiment of the present application can also use other types of electro-optic phase modulators, which can achieve the effect of waveguide transmission on the lithium niobate substrate, and the embodiment of the present application does not make specific limitations.

[0104] It can be understood that since the waveguide stage lithium niobate thin film electro-optic phase modulator adopts lithium niobate material, and the on-chip narrow linewidth laser also adopts lithium niobate material, the on-chip narrow linewidth laser and the lithium niobate thin film electro-optic phase modulator can be integrated on a lithium niobate substrate to realize waveguide transmission.

[0105] Optionally, the MEMS atomic cell is externally provided with a magnetic shield and a temperature control device for reducing the influence of external magnetic field and temperature.

[0106] In the embodiment of the present application, thermal convection and thermal radiation will cause fluctuations in the temperature of the MEMS atomic cell, which in turn causes fluctuations in the atomic number density, thereby affecting the stability, and the external environmental magnetic field will also cause frequency shift changes. Therefore, the magnetic shield and the temperature control device are designed outside the MEMS atomic cell in the chip optical clock to control and shield the temperature of the atomic cell.

[0107] In this way, the magnetic shield and the temperature control device outside the MEMS atomic cell can Figure 2 The stability of the chip optical clock is greatly improved.

[0108] In the foregoing embodiment, the chip optical clock based on the modulation transfer spectrum principle provided by the embodiment of the present application is introduced, and the implementation method of the chip optical clock is described below.

[0109] For example, the present application also provides an implementation method of a chip optical clock based on the modulation transfer spectrum principle, Figure 5 A flowchart of an implementation method of a chip optical clock based on the modulation transfer spectrum principle provided by the embodiment of the present application is shown in Figure 5 The method is applied to a chip optical clock including an on-chip narrow linewidth laser, a waveguide beam splitter, a micro-electro-mechanical system (MEMS) atomic cell, an electro-optic phase modulator, a photodetector, and a high-speed servo feedback control integrated circuit; and the method comprises the following steps.

[0110] S501, the on-chip narrow linewidth laser emits laser light, and the laser light is divided into two beams after passing through the waveguide beam splitter: one beam of laser light is input to the electro-optic phase modulator, and the other beam of laser light is input to the MEMS atomic cell.

[0111] S502, the electro-optic phase modulator performs phase modulation on the input one beam of laser light, and outputs pump light.

[0112] S503, the MEMS atomic cell realizes modulation transfer of the other beam of laser light based on the pump light, and obtains a probe spectrum.

[0113] S504, the photodetector detects the detection spectrum and converts the detection spectrum into an electrical signal.

[0114] S505, the high-speed servo feedback control integrated circuit converts the electrical signal output by the photodetector into a feedback control signal.

[0115] S506, the feedback control port of the on-chip narrow linewidth laser receives the feedback control signal and realizes full-bandwidth locking of the feedback control signal, and outputs an optical clock signal.

[0116] It should be noted that the implementation principle and beneficial effects of the chip optical clock implementation method based on the modulation transfer spectrum principle can be referred to the embodiments shown in Figure 2 The above will not be described here.

[0117] Optionally, the electro-optic phase modulator modulates the phase of the input laser beam and outputs pump light, including:

[0118] The electro-optic phase modulator determines the transition energy level in response to the modulation operation.

[0119] The electro-optic phase modulator adjusts the phase of the input laser beam based on the transition energy level, determines the phase modulation depth, and modulates the laser beam based on the phase modulation depth to output pump light.

[0120] In the embodiments of the present application, the electro-optic phase modulator modulates the phase of the input laser beam, and the purpose is to stabilize the laser frequency to the hyperfine transition of the atomic line.

[0121] For example, if rubidium atoms are selected as quantum references, the corresponding fine energy level 5S 1 / 2 F=2→5P 3 / 2F'=3 as transition energy level (clock transition), 5S 1 / 2 F=2→5P 3 / 2 F'=3 corresponds to a natural line width of about 6MHz, and the modulation frequency is 10MHz.

[0122] Specifically, the electro-optic phase modulator determines the transition energy level as 5S 1 / 2 F=2→5P 3 / 2 F'=3 in response to the modulation operation, for example, if rubidium atoms are selected, and further adjusts the phase of the input laser beam based on the transition energy level to determine the phase modulation depth, such as 1-2 rad, and then modulates the laser beam based on the phase modulation depth of 1-2 rad to output pump light.

[0123] It should be noted that the embodiments of the present application do not make specific limitation on the selected transition energy level, and different atoms can correspond to different transition energy levels.

[0124] Therefore, by stabilizing the laser frequency on the hyperfine transition of the atomic line, the stability of the laser frequency can be improved, and a lower stability can be potentially achieved.

[0125] Optionally, the feedback control port includes a high-speed feedback control port and a slow-speed feedback control port; the high-speed feedback control port is used for stabilizing a high-frequency feedback control signal, and the slow-speed feedback control port is used for stabilizing a low-frequency feedback control signal.

[0126] In the embodiments of the present application, the high-speed servo feedback control circuit can perform feedback control on the power supply, the fast feedback port and the slow feedback port of the on-chip narrow linewidth laser, and is used for realizing high-speed locking of the chip optical clock.

[0127] Specifically, taking Figure 4 for example, after outputting the modulated transfer spectrum signal at the output end of the frequency mixer, the frequency mixer can input the obtained modulated transfer spectrum signal as an error signal to the high-speed servo feedback control circuit to obtain a feedback control signal, and further, the high-speed servo feedback control circuit inputs the feedback control signal to the high-speed feedback control port and the slow-speed feedback control port of the on-chip narrow linewidth laser, thereby completing full-bandwidth locking of the on-chip narrow linewidth laser.

[0128] In this way, through processing of the feedback control signal by the high-speed feedback control port and the slow-speed feedback control port, the stability of the output is greatly improved.

[0129] The above merely serves as a specific implementation of the embodiments of the present application, but the protection scope of the embodiments of the present application is not limited thereto, and any change or replacement within the technical scope disclosed by the embodiments of the present application should be covered in the protection scope of the embodiments of the present application. Therefore, the protection scope of the embodiments of the present application should be subject to the protection scope of the claims.

Claims

1. A chip optical clock based on the principle of modulation transfer spectroscopy, characterized in that, The chip optical clock comprises an on-chip narrow-linewidth laser, a waveguide beam splitter, a micro-electro-mechanical system (MEMS) atomic cell, an electro-optical phase modulator, a photoelectric detector and a high-speed servo feedback control integrated circuit; an output end of the on-chip narrow-linewidth laser is connected with an input end of the waveguide beam splitter, and the on-chip narrow-linewidth laser is used for emitting laser; the waveguide beam splitter is used for splitting the laser into two beams, one of which is used for inputting into the electro-optical phase modulator, and the other of which is used for inputting into the MEMS atomic cell; the electro-optical phase modulator is used for phase modulating the inputted one of the lasers, and outputting pump light; the MEMS atomic cell is used for realizing modulation transfer of the other of the lasers based on the pump light, and obtaining probe spectrum; the photoelectric detector is used for detecting the probe spectrum, and converting the probe spectrum into an electric signal; one end of the high-speed servo feedback control integrated circuit is connected with an output end of the photoelectric detector, and is used for converting the received electric signal outputted by the photoelectric detector into a feedback control signal; the other end of the high-speed servo feedback control integrated circuit is connected with a feedback control port of the on-chip narrow-linewidth laser, the feedback control port is used for receiving the feedback control signal, and realizes full-bandwidth locking of the feedback control signal, and outputs an optical clock signal.

2. The chip optical clock according to claim 1, wherein The high-speed servo feedback control integrated circuit comprises a signal amplifier, a signal generator, a frequency mixer and a high-speed servo feedback control circuit; an input end of the signal amplifier is connected with an output end of the photoelectric detector, and the signal amplifier is used for amplifying the electric signal, and obtaining an amplified signal; an output end of the signal amplifier is connected with one input end of the frequency mixer, one output end of the signal generator is connected with the other input end of the frequency mixer, and the signal generator is used for providing a demodulation signal to the frequency mixer; the frequency mixer is used for receiving the amplified signal and the demodulation signal, and mixing the amplified signal and the demodulation signal, and obtaining a modulation transfer spectrum signal; an output end of the frequency mixer is connected with the high-speed servo feedback control circuit, and the high-speed servo feedback control circuit is used for processing the modulation transfer spectrum signal, and obtaining a feedback control signal.

3. The chip optical clock of claim 2, wherein, The waveguide beam splitter is specifically used for splitting the laser into two beams with different light intensities, one of the lasers with a relatively high light intensity is used as pump laser, and the other of the lasers with a relatively low light intensity is used as probe laser. the other output end of the signal generator is connected with the electro-optical phase modulator, and the signal generator is further used for providing a driving radio frequency signal to the electro-optical phase modulator; the electro-optical phase modulator is specifically used for phase modulating the pump laser based on the driving radio frequency signal, and outputting pump light; the MEMS atomic cell is specifically used for realizing reverse superposition of the pump light and the probe laser, and interacting with quantum reference medium in the MEMS atomic cell, and obtaining probe spectrum.

4. The chip optical clock according to claim 3, wherein, The quantum reference medium in the MEMS atomic cell comprises rubidium atoms or cesium atoms.

5. The chip optical clock of claim 1, wherein, The on-chip narrow-linewidth laser is a micro-ring external cavity laser.

6. The chip optical clock of claim 5, wherein, The electro-optic phase modulator is a waveguide-level lithium niobate thin film electro-optic phase modulator.

7. The chip optical clock according to any one of claims 1 to 6, wherein The MEMS atomic gas cell is externally provided with a magnetic shield and a temperature control device for reducing the influence of external magnetic field and temperature.

8. A method for implementing a chip optical clock based on the principle of modulation transfer spectrum, characterized in that, The chip optical clock comprises an on-chip narrow linewidth laser, a waveguide beam splitter, a MEMS atomic gas cell, an electro-optic phase modulator, a photodetector and a high-speed servo feedback control integrated circuit. The on-chip narrow linewidth laser emits laser light, which is split into two beams after passing through the waveguide beam splitter: one beam of laser light is input into the electro-optic phase modulator, and the other beam of laser light is input into the MEMS atomic gas cell. The electro-optic phase modulator modulates the phase of the input laser light and outputs pump light. The MEMS atomic gas cell modulates and shifts the other beam of laser light based on the pump light to obtain a probe spectrum. The photodetector detects the probe spectrum and converts the probe spectrum into an electrical signal. The high-speed servo feedback control integrated circuit converts the electrical signal output by the photodetector into a feedback control signal. The feedback control port of the on-chip narrow linewidth laser receives the feedback control signal and realizes full-bandwidth locking of the feedback control signal to output an optical clock signal.

9. The implementation method of claim 8, wherein, The electro-optic phase modulator modulates the phase of the input laser light and outputs pump light, including: The electro-optic phase modulator determines a transition energy level in response to a modulation operation. The electro-optic phase modulator adjusts the phase of the input laser light based on the transition energy level, determines a phase modulation depth, and modulates the laser light based on the phase modulation depth to output pump light.

10. The implementation method of claim 8, wherein, The feedback control port comprises a high-speed feedback control port and a slow-speed feedback control port; the high-speed feedback control port is used to stabilize a high-frequency feedback control signal, and the slow-speed feedback control port is used to stabilize a low-frequency feedback control signal.

Images