Chip active optical clock based on MEMS atomic gas cell and implementation method thereof

Abstract

The application discloses a chip active optical clock based on a MEMS atomic gas chamber and an implementation method thereof. The application pumps the gain medium in the MEMS atomic gas chamber by laser, establishes population inversion, and through the cavity feedback of the resonant cavity, continuously amplifies the spontaneous radiation to reach the laser threshold, and then outputs the active lasing signal. Since the resonant cavity for generating the active lasing signal is a bad cavity, the gain line width is much smaller than the cavity mode line width, the noise caused by the cavity dragging effect can be greatly suppressed, and the output laser can be directly used as an optical frequency standard signal without the need of a servo circuit to stabilize the resonant cavity length, thereby reducing the volume and power consumption of the system. Meanwhile, the MEMS atomic gas chamber is used as a core component, various optoelectronic components are assembled in a stacking mode and integrated on a silicon-based chip, and the chip microcavity optical comb is combined to perform frequency down-conversion, so that the chip active optical clock with a narrow line width and high stability is realized. The application provides a new way for the deployment of the active optical clock in miniaturized and portable time-frequency devices.

Description

Technical Field

[0001] This invention belongs to the field of micro atomic clock technology, specifically relating to a chip-based active optical clock based on a MEMS atomic gas cell and its implementation method. Background Technology

[0002] For nearly a century, optical atomic (molecular) frequency references have played a crucial role in scientific research and engineering, providing standards for achieving precise measurements. Since the concept of the laser was first proposed in 1958, the scientific community has been exploring ways to use lasers to improve the accuracy of time measurement. Currently, the performance of optical frequency atomic clocks (hereinafter referred to as optical clocks) has surpassed that of microwave atomic clocks, with the best optical clocks achieving stability and uncertainty levels approaching 10⁻⁶. -19 Lightning speed. Optical clocks have been widely used in fundamental physics research, such as dark matter detection, verification of general relativity, gravitational wave detection, and the variation of physical constants over time, providing a powerful tool for understanding the universe and the microscopic world. Furthermore, they have extensive applications in optical communication, enabling the construction of high-speed communication systems, ensuring precise synchronization of data transmission, and improving the performance and stability of communication networks. Simultaneously, optical clocks support critical applications such as global navigation satellite systems, geographic information systems, and financial transactions, and are being deployed to redefine the second using optical clocks, which is of great significance for establishing international time standards.

[0003] Traditional optical clocks are passive, requiring an external quantum frequency reference. A servo feedback circuit locks the local oscillator laser frequency to this quantum frequency reference, thus stabilizing the laser's frequency. The local oscillator laser in a passive optical clock operates in the good cavity region, where the cavity mode linewidth is much smaller than the gain linewidth. The stability of its output optical frequency standard signal is limited by the cavity length stability, and cavity length thermal noise directly affects the short-term frequency stability of the passive optical clock. In contrast, active optical clocks do not require an external frequency reference. They directly use the stimulated emission signal of atoms as the frequency standard and operate in the bad cavity region, where the gain linewidth is much smaller than the cavity mode linewidth. The output laser frequency depends on the center frequency of the quantum reference, naturally suppressing cavity pulling effects and resulting in better short-term frequency stability. In summary, active optical clocks offer advantages over passive optical clocks, including cavity pulling suppression, narrow linewidth, excellent short-term frequency stability, and system simplicity, making them promising for broad applications. Combining them with MEMS technology can further simplify system size and power consumption, enabling the creation of chip-based optical clocks for use in mobile military equipment, providing them with time and frequency references with timing capabilities and high frequency stability.

[0004] Microelectromechanical systems (MEMS) technology employs silicon wafer etching techniques similar to semiconductor processing, achieving extremely high processing precision. This precision is applied to the miniaturization of various mechanical components and serves the manufacturing of chip-based atomic clocks. One key micro-quantum component is the MEMS atomic gas cell. While maintaining performance, the MEMS atomic gas cell is only a few millimeters or less than one millimeter thick, with a total volume far smaller than traditional atomic gas cells, making it a crucial component for the miniaturization of atomic clocks. Meanwhile, in recent years, the rapid development of micro-optical components such as novel microcavity optical combs (hereinafter referred to as microcavity optical combs), distributed Bragg reflection (DBR) narrow-linewidth lasers, and thin-film photodetectors has promoted the improvement of chip-based optical system integration. Based on MEMS atomic gas cells and active optical clock technology, combined with micro-optical components, small-volume, low-power chip-level active optical clocks can be realized. However, there are currently no reports of chip-based active optical clocks based on MEMS atomic gas cells. Summary of the Invention

[0005] The technical problem to be solved by this invention is: how to provide a chip-based active optical clock based on MEMS atomic gas cells and its implementation method, requiring that the technical solution be simple and reliable, and have a small size and power consumption.

[0006] This invention utilizes a saturated absorption spectrum frequency-stabilized light source to pump atoms in a MEMS atomic gas cell. The resulting stimulated emission laser is directly used as the optical frequency standard output. After being beat with a microcavity optical comb, it realizes an active optical clock on the chip, which greatly reduces the size of the system. It can stack optoelectronic devices vertically and integrate them on the chip, making it suitable for compact and portable device applications.

[0007] To address the aforementioned technical problems, this invention provides a chip-based active optical clock based on a MEMS atomic gas cell. It determines the gain medium and target transition energy level according to the target wavelength, and generates an optical signal of the target wavelength when spontaneous emission occurs after the population inversion of particles at the target transition energy level. Taking cesium atoms as the gain medium as an example, it includes:

[0008] DBR-pumped laser 1 is used to generate narrow-linewidth pump light at a wavelength of 455 nm, corresponding to cesium atoms from 6S... 1 / 2 State to 7P 3 / 2 The transition between states pumps particles from low to high energy levels in the target transition energy level of the gain medium to achieve population inversion.

[0009] Laser controller 2 is used to control the temperature and current of DBR pump laser source 1, thereby controlling the output frequency of DBR pump laser source 1 and scanning the output frequency; simultaneously, it receives the saturated absorption spectrum electrical signal, calculates the frequency error of DBR pump laser source 1, and adjusts the output frequency of DBR pump laser source 1 in real time for correction, locking the output frequency at the cesium atom from 6S1 / 2 State to 7P 3 / 2 At a wavelength of 455nm corresponding to the state transition frequency;

[0010] The half-wave plate 3 and the polarizing beam splitter 4 are used to control the power of the pump light passing through the polarizing beam splitter 4 for the 455nm pump light from the DBR pump laser 1. The pump light transmitted through the polarizing beam splitter 4 is then incident on the first MEMS atomic gas cell 6.

[0011] The first thin-film photodetector 5 is used to convert the saturated absorption spectrum optical signal into an electrical signal and transmit it to the laser controller 2.

[0012] The first MEMS atomic gas chamber 6 has two windows on the two surfaces through which the laser passes. Taking cesium atoms as an example, the windows are coated with a dielectric film that enhances the transmission of 455nm pump light. Through the interaction between the laser and the atoms, a saturated absorption spectrum light signal can be generated as a reference for frequency stabilization.

[0013] Partial reflector 7 is used to partially reflect the light that passes through the first MEMS atomic gas cell 6 back. The reflected light is used as saturated absorption spectrum detection light, which passes through the first MEMS atomic gas cell 6 in the opposite direction to form a saturated absorption spectrum light signal, and is reflected to the first thin film photodetector 5 by polarization beam splitter 4.

[0014] The second MEMS atomic gas chamber 8 and the resonant cavity mirror 9 are described. The second MEMS atomic gas chamber 8 has two windows on its two laser-transmitting surfaces. Taking cesium atoms as an example, the window furthest from the resonant cavity mirror 9 (hereinafter referred to as the front window) and the resonant cavity mirror 9 are both coated with a dielectric film that is highly transparent to 455nm pump light and has a certain reflectivity to the target wavelength (1470nm for cesium atoms). This allows the front window of the second MEMS atomic gas chamber 8 and the resonant cavity mirror 9 to form a resonant cavity. The second MEMS atomic gas chamber 8 is filled with an appropriate amount of pure cesium atoms as a gain medium. Pump light, partially reflected by the mirror 7, enters the resonant cavity through the front window. Under the pumping of the 455nm pump light, cesium atoms undergo a 6S... 1 / 2 State to 7P 3 / 2 The energy level transition of the cesium atom is followed by a spontaneous emission to a lower energy level, thus establishing the cesium atom 7S. 1 / 2 State and 6P 3 / 2 The population inversion between states generates a 1470nm fluorescence signal within the resonant cavity due to spontaneous emission. The resonant cavity continuously amplifies the 1470nm fluorescence signal generated after pumping the cesium atoms in the gain medium until a stimulated emission signal light with a target wavelength of 1470nm is formed. This stimulated emission signal serves as the optical frequency standard signal (hereinafter referred to as the optical frequency standard signal) of this active optical clock and is output through the resonant cavity mirror 9.

[0015] The microcavity optical comb 10 is used to generate a series of comb tooth optical signals with equal frequency intervals.

[0016] The polarization beam splitter 11 is used to combine the 1470nm wavelength optical frequency standard signal output by the resonant cavity mirror 9 and the comb optical signal generated by the microcavity optical comb 10 to generate a beat frequency optical signal, thereby downconverting the optical frequency.

[0017] The second thin-film photodetector 12 is used to receive beat frequency optical signals and convert them into electrical signals.

[0018] The digital frequency counter 13 is used to receive the beat frequency electrical signal from the second thin-film photodetector 12 for measurement, and output a clock signal after processing to realize the chip's active optical clock.

[0019] The resonant cavity mirror 9 can be a plano-concave lens or a planar lens, and the parameters of the resonant cavity are calculated so that its cavity mode linewidth is much larger than the gain linewidth of cesium atoms in the second MEMS atomic gas cell 8, that is, so that the optical clock operates in the bad cavity region.

[0020] The chip-based active optical clock also includes a window (rear window) on one side of the second MEMS atomic gas chamber 8 near the resonant cavity mirror 9, which is coated with a dielectric film that is highly transparent to both 455nm wavelength pump light and 1470nm wavelength optical frequency standard signal.

[0021] The chip-based active optical clock also includes an external magnetic shielding module for the first MEMS atomic gas chamber 6 and the second MEMS atomic gas chamber 8, as well as heating, heat preservation, and temperature control modules. It can heat the atomic gas chamber to 200°C and achieve a temperature control accuracy of 0.001°C, thereby isolating the influence of external magnetic fields and temperature fluctuations on the transition frequency of cesium atoms.

[0022] Furthermore, this invention also provides a method for implementing a chip-based active optical clock based on a MEMS atomic gas cell, specifically including the following steps:

[0023] Step S1: The DBR pump laser 1 adjusts its current and temperature through the laser controller 2, thereby adjusting the frequency of the DBR pump laser 1 to match that of cesium atoms 6S. 1 / 2 State to 7P 3 / 2 The frequency correspondence of the state transitions is determined, and the frequency is swept accordingly;

[0024] Step S2: The frequency of the DBR pump laser 1 is adjusted to match that of cesium atoms 6S 1 / 2 State to 7P 3 / 2 After the state transition frequency resonates, the half-wave plate 3 is adjusted to make the power of the 455nm pump light transmitted through the polarizing beam splitter 4 appropriate.

[0025] Step S3: The temperature of the first MEMS atomic gas chamber 6 and the second MEMS atomic gas chamber 8 are controlled by the temperature control device to keep them at the working temperature points between 90 degrees Celsius and 200 degrees Celsius, thereby meeting the atomic number conditions required for laser oscillation.

[0026] Step S4: The transmitted light from the polarizing beam splitter 4 passes through the first MEMS atomic gas cell 6 and is partially reflected on the partial reflector 7.

[0027] Step S5: The reflected light on the partial reflector 7 is used as the saturated absorption spectrum detection light and passes through the first MEMS atomic gas cell 6 in the reverse direction to generate a saturated absorption spectrum light signal.

[0028] Step S6: The saturated absorption spectrum light signal is reflected on the polarization beam splitter 4, enters the first thin-film photodetector 5, is converted into an electrical signal, and is fed back to the laser controller 2 to lock the frequency of the 455nm pump light of the DBR pump laser 1 at cesium atom 6S. 1 / 2 State to 7P 3 / 2 Achieve frequency stabilization of the saturated absorption spectrum at the state transition frequency;

[0029] Step S7: The 455nm pump light, after being stabilized by the saturated absorption spectrum, passes through the window of the second MEMS atomic gas cell 8 and enters the resonant cavity;

[0030] Step S8: Inside the second MEMS atomic gas chamber 8, the 455nm pump light propels cesium atoms from 6S... 1 / 2 State pump to 7P 3 / 2 State, 7P 3 / 2 Cesium atoms in the 7S state undergo spontaneous emission to eventually form the cesium atom 7S. 1 / 2 State and 6P 3 / 2 Population reversal between states;

[0031] Step S9: Under the gain effect of the second MEMS atomic gas cell 8, and under the enhancement effect of the resonant cavity composed of the front window of the second MEMS atomic gas cell 8 and the resonant cavity mirror 9, and at the same time, when the 455nm pump light power reaches a suitable value, the gain for the 1470nm fluorescence signal is greater than the loss, thereby realizing the 1470nm stimulated emission signal light as an optical frequency standard signal.

[0032] Step S10: Output a 1470nm optical frequency standard signal through the resonant cavity mirror 9;

[0033] Step S11: The optical frequency standard signal is combined with the comb-tooth optical signal generated by the microcavity optical comb 10 in the polarization beam splitter 11 to generate a beat frequency optical signal;

[0034] Step S12: The beat frequency optical signal enters the second thin-film photodetector 12, is converted into a beat frequency electrical signal, inputs into the digital frequency counter 13, and after a series of digital operations, outputs a time signal to realize the chip's active optical clock.

[0035] The method further includes: the center wavelength of the DBR pump laser 1 can be changed to 459 nm, and the saturation absorption spectrum is locked to cesium atoms from 6S 1 / 2 State to 7P 1 / 2 The transition frequency of the state is adjusted so that the cesium atoms in the second MEMS atomic chamber 8 are moved from the 6S state. 1 / 2 State pump to 7P 1 / 2 Similarly, it can output an optical frequency standard signal with a center wavelength of 1470nm, realizing the steps of chip active optical clock.

[0036] The method further includes: the center wavelength of the DBR pump laser 1 can be replaced with 421 nm, the atom type in the first MEMS atomic gas chamber 6 and the second MEMS atomic gas chamber 8 can be changed to rubidium atoms, and the DBR pump laser 1 is locked to rubidium atoms from 5 s using a saturated absorption spectrum. 1 / 2 State to 6P 1 / 2 The transition frequency of the state is adjusted so that the rubidium atoms in the second MEMS atomic gas chamber 8 are moved from the 5S transition frequency. 1 / 2 State pump to 6P 1 / 2 The process involves outputting an optical frequency standard signal with a center wavelength of 1367nm to realize the chip's active optical clock.

[0037] Compared with the prior art, the positive effects of the present invention are as follows:

[0038] This invention uses cesium atoms in a MEMS atomic gas cell as the gain medium (rubidium or potassium atoms, or other alkali metal atoms, can also be used). Using 455nm pump light, cesium atoms are drawn from a 6S… 1 / 2 State pump to 7P 3 / 2 The state, through spontaneous emission, in the cesium atom 7S 1 / 2 State and 6P 3 / 2 Population inversion is established between states, and through cavity feedback of the resonant cavity, the corresponding cesium atom 7S is made to... 1 / 2 State and 6P 3 / 2The spontaneous emission of the state transition is continuously amplified, and after reaching the laser threshold, it outputs a 1470nm stimulated emission signal light, which is directly used as an optical frequency standard signal. Since the active optical clock operates in the bad cavity region, its gain linewidth is much smaller than the cavity mode linewidth, which greatly suppresses the influence of cavity pulling effect on short-term frequency stability. Compared with traditional passive optical clocks, it eliminates the need for complex high-precision servo circuits to stabilize the resonant cavity length, reducing the system's size and power consumption. Furthermore, using a MEMS atomic gas cell as the core component and replacing traditional optoelectronic components with miniature components, these components are stacked and integrated onto a silicon-based chip. Combined with a chip-based microcavity optical comb for frequency down-conversion, a narrow-linewidth, high-stability chip-based active optical clock is achieved, with even higher stability compared to existing chip-based microwave atomic clocks. This invention has significant application value, providing a long-term, high-precision frequency reference for mobile devices. Attached Figure Description

[0039] Figure 1 This invention provides a schematic diagram of a chip-based active optical clock with a MEMS atomic gas cell.

[0040] Figure 2 This is a schematic diagram of the energy level structure of cesium and rubidium atoms involved in the implementation of this invention;

[0041] (a) is a schematic diagram of the energy level structure of a cesium atom, and (b) is a schematic diagram of the energy level structure of a rubidium atom. Detailed Implementation

[0042] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0043] To address the problems of existing technologies, this invention provides a chip-based active optical clock using a MEMS atomic gas cell, taking cesium atoms as the gain medium as an example, such as... Figure 1 As shown, the device includes:

[0044] DBR-pumped laser 1 is used to generate narrow-linewidth pump light at a wavelength of 455 nm, corresponding to cesium atoms from 6S... 1 / 2 State to 7P 3 / 2 The transition between states pumps particles from low to high energy levels in the target transition energy level of the gain medium to achieve population inversion.

[0045] Laser controller 2 is used to control the temperature and current of DBR pump laser source 1, thereby controlling the output frequency of DBR pump laser source 1 and scanning the output frequency; simultaneously, it receives the saturated absorption spectrum electrical signal, calculates the frequency error of DBR pump laser source 1, and adjusts the output frequency of DBR pump laser source 1 in real time for correction, locking the output frequency at the cesium atom from 6S 1 / 2 State to 7P 3 / 2 At a wavelength of 455nm corresponding to the state transition frequency;

[0046] The half-wave plate 3 and the polarizing beam splitter 4 are used to control the power of the pump light passing through the polarizing beam splitter 4 for the 455nm pump light from the DBR pump laser 1. The pump light transmitted through the polarizing beam splitter 4 is then incident on the first MEMS atomic gas cell 6.

[0047] The first thin-film photodetector 5 is used to convert the saturated absorption spectrum optical signal into an electrical signal and transmit it to the laser controller 2.

[0048] The first MEMS atomic gas chamber 6 has two windows on the two surfaces through which the laser passes. Taking cesium atoms as an example, the windows are coated with a dielectric film that enhances the transmission of 455nm pump light. Through the interaction between the laser and the atoms, a saturated absorption spectrum light signal can be generated as a reference for frequency stabilization.

[0049] Partial reflector 7 is used to partially reflect the light that passes through the first MEMS atomic gas cell 6 back. The reflected light is used as saturated absorption spectrum detection light, which passes through the first MEMS atomic gas cell 6 in the opposite direction to form a saturated absorption spectrum light signal, and is reflected to the first thin film photodetector 5 by polarization beam splitter 4.

[0050] The second MEMS atomic gas chamber 8 and the resonant cavity mirror 9 are described. The second MEMS atomic gas chamber 8 has two windows on its two laser-transmitting surfaces. Taking cesium atoms as an example, the window furthest from the resonant cavity mirror 9 (hereinafter referred to as the front window) and the resonant cavity mirror 9 are both coated with a dielectric film that is highly transparent to 455nm pump light and has a certain reflectivity to the target wavelength (1470nm for cesium atoms). This allows the front window of the second MEMS atomic gas chamber 8 and the resonant cavity mirror 9 to form a resonant cavity. The second MEMS atomic gas chamber 8 is filled with an appropriate amount of pure cesium atoms as a gain medium. Pump light, partially reflected by the mirror 7, enters the resonant cavity through the front window. Under the pumping of the 455nm pump light, cesium atoms undergo a 6S... 1 / 2 State to 7P 3 / 2 The energy level transition of the cesium atom is followed by a spontaneous emission to a lower energy level, thus establishing the cesium atom 7S. 1 / 2 State and 6P 3 / 2The population inversion between states generates a 1470nm fluorescence signal within the resonant cavity due to spontaneous emission. The resonant cavity continuously amplifies the 1470nm fluorescence signal generated after pumping the cesium atoms in the gain medium until a stimulated emission signal light with a target wavelength of 1470nm is formed. This stimulated emission signal serves as the optical frequency standard signal (hereinafter referred to as the optical frequency standard signal) of this active optical clock and is output through the resonant cavity mirror 9.

[0051] The microcavity optical comb 10 is used to generate a series of comb tooth optical signals with equal frequency intervals.

[0052] The polarization beam splitter 11 is used to combine the 1470nm wavelength optical frequency standard signal output by the resonant cavity mirror 9 and the comb optical signal generated by the microcavity optical comb 10 to generate a beat frequency optical signal, thereby downconverting the optical frequency.

[0053] The second thin-film photodetector 12 is used to receive beat frequency optical signals and convert them into electrical signals.

[0054] The digital frequency counter 13 is used to receive the beat frequency electrical signal from the second thin-film photodetector 12 for measurement, and output a clock signal after processing to realize the chip's active optical clock.

[0055] The resonant cavity mirror 9 can be a plano-concave lens or a planar lens, and the parameters of the resonant cavity are calculated so that its cavity mode linewidth is much larger than the gain linewidth of cesium atoms in the second MEMS atomic gas cell 8, that is, so that the optical clock operates in the bad cavity region.

[0056] The chip-based active optical clock also includes a window (rear window) on one side of the second MEMS atomic gas chamber 8 near the resonant cavity mirror 9, which is coated with a dielectric film that is highly transparent to wavelengths of 455nm and 1470nm.

[0057] The chip-based active optical clock also includes an external magnetic shielding module for the first MEMS atomic gas chamber 6 and the second MEMS atomic gas chamber 8, as well as heating, heat preservation, and temperature control modules. It can heat the atomic gas chamber to 200°C and achieve a temperature control accuracy of 0.001°C, thereby isolating the influence of external magnetic fields and temperature fluctuations on the transition frequency of cesium atoms.

[0058] Furthermore, the present invention also provides a method for implementing a chip-based active optical clock based on a MEMS atomic gas cell, the method being implemented according to the aforementioned apparatus, and including the following steps:

[0059] Step S1: The DBR pump laser 1 is adjusted in terms of current and temperature by the laser controller 2, thereby adjusting the frequency of the DBR pump laser 1 to match that of cesium atoms 6S 1 / 2 State to 7P 3 / 2 The frequency correspondence of the state transitions is determined, and the frequency is swept accordingly;

[0060] Step S2: The frequency of the DBR pump laser 1 is adjusted to match that of cesium atoms 6S 1 / 2 State to 7P 3 / 2 After the state transition frequency resonates, the half-wave plate 3 is adjusted to make the power of the 455nm pump light transmitted through the polarizing beam splitter 4 appropriate.

[0061] Step S3: The temperature of the first MEMS atomic gas chamber 6 and the second MEMS atomic gas chamber 8 are controlled by the temperature control device to keep them at the working temperature points between 90 degrees Celsius and 200 degrees Celsius, thereby meeting the atomic number conditions required for laser oscillation.

[0062] Step S4: The transmitted light from the polarizing beam splitter 4 passes through the first MEMS atomic gas cell 6 and is partially reflected on the partial reflector 7.

[0063] Step S5: The reflected light on the partial reflector 7 is used as the saturated absorption spectrum detection light and passes through the first MEMS atomic gas cell 6 in the reverse direction to generate a saturated absorption spectrum light signal.

[0064] Step S6: The saturated absorption spectrum light signal is reflected on the polarization beam splitter 4, enters the first thin-film photodetector 5, is converted into an electrical signal, and is fed back to the laser controller 2 to lock the frequency of the 455nm pump light of the DBR pump laser 1 at cesium atom 6S. 1 / 2 State to 7P 3 / 2 Achieve frequency stabilization of the saturated absorption spectrum at the state transition frequency;

[0065] Step S7: The 455nm pump light, after being stabilized by the saturated absorption spectrum, passes through the window of the second MEMS atomic gas cell 8 and enters the resonant cavity;

[0066] Step S8: Inside the second MEMS atomic gas chamber 8, the 455nm pump light propels cesium atoms from 6S... 1 / 2 State pump to 7P 3 / 2 State, 7P 3 / 2 Cesium atoms in the 7S state undergo spontaneous emission to eventually form the cesium atom 7S. 1 / 2 State and 6P 3 / 2 Population reversal between states;

[0067] Step S9: Under the gain effect of the second MEMS atomic gas cell 8, and under the enhancement effect of the resonant cavity composed of the front window of the second MEMS atomic gas cell 8 and the resonant cavity mirror 9, and at the same time, when the 455nm pump light power reaches a suitable value, the gain for the 1470nm fluorescence signal is greater than the loss, thereby realizing the 1470nm stimulated emission signal light as an optical frequency standard signal.

[0068] Step S10: Output a 1470nm optical frequency standard signal through the resonant cavity mirror 9;

[0069] Step S11: The optical frequency standard signal is combined with the comb-tooth optical signal generated by the microcavity optical comb 10 in the polarization beam splitter 11 to generate a beat frequency optical signal;

[0070] Step S12: The beat frequency optical signal enters the second thin-film photodetector 12, is converted into a beat frequency electrical signal, inputs into the digital frequency counter 13, and after a series of digital operations, outputs a time signal to realize the chip's active optical clock.

[0071] The method further includes: the center wavelength of the DBR pump laser 1 can be changed to 459 nm, and the saturation absorption spectrum is locked to cesium atoms from 6S 1 / 2 State to 7P 1 / 2 The transition frequency of the state is adjusted so that the cesium atoms in the second MEMS atomic chamber 8 are moved from the 6S state. 1 / 2 State pump to 7P 1 / 2 The state was established to establish the cesium atom 7S 1 / 2 State and 6P 3 / 2 Population inversion between states can also output an optical frequency standard signal with a center wavelength of 1470nm, realizing the steps of chip-based active optical clock.

[0072] The method further includes: the center wavelength of the DBR pump laser 1 can be replaced with 421 nm, the atom type in the first MEMS atomic gas chamber 6 and the second MEMS atomic gas chamber 8 can be changed to rubidium atoms, and the DBR pump laser 1 is locked to rubidium atoms from 5 s using a saturated absorption spectrum. 1 / 2 State to 6P 1 / 2 The transition frequency of the state is adjusted so that the rubidium atoms in the second MEMS atomic gas chamber 8 are moved from the 5S transition frequency. 1 / 2 State pump to 6P 1 / 2 The state was established to establish the rubidium atom 6S 1 / 2 State and 5P 3 / 2 The population inversion between states outputs an optical frequency standard signal with a center wavelength of 1367nm, realizing the chip's active optical clock process.

[0073] The following is a detailed description with reference to specific embodiments.

[0074] Example

[0075] In this embodiment, as Figure 1As shown, a chip-based active optical clock device based on a MEMS atomic gas cell includes: a DBR pump laser 1, a laser controller 2, a half-wave plate 3, a polarizing beam splitter 4, a first thin-film photodetector 5, a first MEMS atomic gas cell 6, a partial reflector 7, a second MEMS atomic gas cell 8, a resonant cavity mirror 9, a microcavity optical comb 10, a polarizing beam splitter 11, a second thin-film photodetector 12, and a digital frequency counter 13.

[0076] The 455nm pump light output from DBR pump laser 1 pumps cesium atoms to 7P. 3 / 2 The state, through spontaneous emission, in the cesium atom 7S 1 / 2 State and 6P 3 / 2 Population inversion is established between states. The first MEMS atomic gas cell 6 serves as a frequency reference for stabilizing the saturated absorption spectrum. The partial reflector 7 is used to generate saturated absorption spectrum probe light. The first thin-film photodetector 5 is used to receive the saturated absorption spectrum light signal and convert it into an electrical signal. The half-wave plate 3 is used to adjust the power of the 455nm pump light transmitted through the polarization beam splitter 4. The polarization beam splitter 4 is used to reflect the saturated absorption spectrum light signal onto the first thin-film photodetector 5. The laser controller 2 is used to adjust and lock the laser frequency of the DBR pump laser 1. The second MEMS atomic gas cell 8 is used to provide a 1470nm optical frequency standard signal. The resonant cavity mirror 9 is used to form a resonant cavity with the front window dielectric film of the second MEMS atomic gas cell 8. The microcavity optical comb 10 is used to generate a comb signal. The polarization beam splitter 11 is used to beat the optical frequency standard signal with the comb signal. The second thin-film photodetector 12 is used to detect the beat signal. The digital frequency counter 13 is used to process the beat signal and output a clock signal.

[0077] like Figure 2 As shown in the diagram, the 455nm pump light output from the DBR pump laser 1 raises the cesium atoms in the second MEMS atomic gas chamber 8 from the 6S... 1 / 2 Pump to 7P 3 / 2 The state, through spontaneous emission, in the cesium atom 7S 1 / 2 State and 6P 3 / 2 Population inversion is established between states. The front window dielectric film of the second MEMS atomic gas cell 8 and the resonant cavity mirror 9 provide optical feedback for the 1470nm wavelength laser. By adjusting the temperature of the second MEMS atomic gas cell 8 and the power of the pump light transmitted through the polarization beam splitter 4, when the gain is greater than the loss, the 1470nm stimulated emission signal light is realized and output from the resonant cavity mirror 9 as an optical frequency standard signal.

[0078] Another embodiment of the present invention is to replace the DBR pump laser 1 in the above embodiment with a DBR laser with a center wavelength of 459 nm, and lock the cesium atom from 6S through saturation absorption spectrum. 1 / 2 State to 7P1 / 2 At the transition frequency of the state, the cesium atoms in the second MEMS atomic gas chamber 8 are moved from the 6S state. 1 / 2 State pump to 7P 1 / 2 The state can also be achieved in 7S. 1 / 2 State and 6P 3 / 2 Population inversion is established between states, and an optical frequency standard signal with a center wavelength of 1470 nm is output. Other techniques and methods are consistent with the implementation of the chip-based active optical clock based on the cesium atom 1470 nm optical frequency standard signal.

[0079] Another embodiment of the present invention is to replace the DBR pump laser 1 in the above embodiment with a DBR laser with a center wavelength of 421 nm, and lock the rubidium atoms from 5S atoms using the saturated absorption spectrum. 1 / 2 State to 6P 1 / 2 At the transition frequency of the states, cesium atoms in the second MEMS atomic gas chamber 8 are replaced with rubidium atoms, enabling the resonant cavity composed of the front window of the second MEMS atomic gas chamber 8 and the resonant cavity mirror 9 to have optical feedback capability for 1367nm laser. The energy level diagram of rubidium atoms is shown below. Figure 2 From the energy level diagram, when the DBR pump laser 1 interacts with rubidium atoms 5S... 1 / 2 State to 6P 1 / 2 At the resonant frequency of the state transition, rubidium atoms in the second MEMS atomic chamber 8 transition from 5S to the state transition frequency. 1 / 2 The state is pumped to 6P 1 / 2 The state of rubidium atoms 6S 1 / 2 State and 5P 3 / 2 Population inversion is established between states. The resonant cavity, consisting of the front window of the second MEMS atomic gas cell 8 and the resonant cavity mirror 9, provides optical feedback for the 1367nm wavelength laser. By adjusting the temperature of the second MEMS atomic gas cell 8 and the power of the pump light transmitted through the polarization beam splitter prism 4, when the gain is greater than the loss, a 1367nm stimulated emission signal light is achieved and output as an optical frequency standard signal from the resonant cavity mirror 9. Other techniques and methods are consistent with the embodiment of the chip-based active optical clock based on the 1470nm optical frequency standard signal of cesium atoms.

[0080] The power of the pump light transmitted through the polarizing beam splitter 4 is adjusted by adjusting the angle of the half-wave plate 3.

[0081] The parameters of the resonant cavity composed of the front window dielectric film of the second MEMS atomic gas cell 8 and the resonant cavity mirror 9 need to be calculated so that its cavity mode linewidth is much larger than the gain linewidth of the atoms in the second MEMS atomic gas cell 8, that is, so that the optical clock works in the bad cavity region.

[0082] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A chip-based active optical clock based on a MEMS atomic gas cell, characterized in that, It includes a pump laser (1), a saturated absorption spectrum frequency stabilization module, a resonant cavity, a second MEMS atomic gas cell (8), a microcavity optical comb (10), a polarization beam splitter (11), a second thin-film photodetector (12), and a digital frequency counter (13). The second MEMS atomic gas chamber (8) is located inside the resonant cavity; The pump laser (1) is used to output pump light to pump the gain medium in the second MEMS atomic gas cell (8), first pumping the particles on the low energy level of the gain medium to the high energy level, and then realizing the population inversion of the particles on the target transition energy level through spontaneous emission; wherein the gain medium and the target transition energy level are determined according to the target wavelength of the active optical clock, so as to generate the fluorescence signal of the target wavelength when spontaneous emission is generated after the population inversion of the particles on the target transition energy level, and generate the stimulated emission signal of the target wavelength after amplification by the resonant cavity, which is used as the optical frequency standard signal output of the active optical clock of the chip; The saturated absorption spectrum frequency stabilization module is used to stabilize the frequency of the pump light output by the pump laser (1); The microcavity optical comb (10) is used to generate comb tooth optical signals; The polarizing beam splitter (11) is used to combine the optical frequency standard signal and the comb optical signal to generate a beat frequency optical signal. The second thin-film photodetector (12) is used to receive beat frequency optical signals and convert them into beat frequency electrical signals; The digital frequency counter (13) is used to measure the beat frequency electrical signal and process it to output a clock signal, thereby realizing the chip's active optical clock. The saturated absorption spectrum frequency stabilization module includes a laser controller (2), a beam adjustment device, a first thin-film photodetector (5), a first MEMS atomic gas cell (6), and a partial reflector (7). The laser controller (2) is used to control the output frequency of the pump laser (1) according to the received saturated absorption spectrum electrical signal; The beam adjustment device is used to adjust the pump light power output by the pump laser (1) and input it to the first MEMS atomic gas cell (6), and to input the received saturated absorption spectrum light signal to the first thin film photodetector (5). The first thin-film photodetector (5) is used to convert the saturated absorption spectrum optical signal into an electrical signal and transmit it to the laser controller (2). The partial reflector (7) reflects part of the light output from the first MEMS atomic gas cell (6) back to the first MEMS atomic gas cell (6). In the first MEMS atomic gas cell (6), two laser beams propagating in opposite directions interact with atoms to form a saturated absorption spectrum light signal, which is then input to the first thin-film photodetector (5) through a beam adjustment device.

2. The chip-based active optical clock according to claim 1, characterized in that, The beam adjustment device includes a half-wave plate (3) and a polarizing beam splitter (4); the half-wave plate (3) is adjusted to control the power of the pump light passing through the polarizing beam splitter (4), and the pump light transmitted through the polarizing beam splitter (4) is incident on the first MEMS atomic gas cell (6).

3. The chip-based active optical clock according to claim 1 or 2, characterized in that, The front window of the second MEMS atomic gas chamber (8) is coated with a dielectric film that is highly transparent to the pump light and has a certain reflectivity to the target wavelength as the front cavity mirror of the resonant cavity, and the rear end of the second MEMS atomic gas chamber (8) is provided with a resonant cavity mirror (9) as the rear cavity mirror of the resonant cavity.

4. The chip-based active optical clock according to claim 3, characterized in that, The resonant cavity mirror (9) is coated with a dielectric film that is highly transparent to the pump light and has a certain reflectivity to the target wavelength; the window of the first MEMS atomic gas chamber (6) is coated with a dielectric film that enhances the transparency of the pump light.

5. The chip-based active optical clock according to claim 1 or 2, characterized in that, The cavity mode linewidth of the resonant cavity is much larger than the gain linewidth of cesium atoms in the second MEMS atomic gas chamber (8), that is, the chip active optical clock is operating in the bad cavity region.

6. The chip-based active optical clock according to claim 1 or 2, characterized in that, Both the first MEMS atomic gas chamber (6) and the second MEMS atomic gas chamber (8) are equipped with a magnetic shielding module and a temperature control module, which are used to heat the atomic gas chamber to 200°C and achieve a temperature control accuracy of 0.001°C.

7. The chip-based active optical clock according to claim 1 or 2, characterized in that, If the gain medium is cesium atoms, the target transition level is 6P. 3 / 2 and 7P 1 / 2 Energy level; if the gain medium is rubidium atoms, the target transition energy level is 5P. 3 / 2 and 6S 1 / 2 energy level.

8. A method for implementing a chip-based active optical clock based on the MEMS atomic gas cell of claim 1, comprising the following steps: 1) The pump light output from the pump laser (1) stabilized by the saturated absorption spectrum stabilization module is used to pump the gain medium in the second MEMS atomic gas chamber (8). First, the particles on the low energy level of the gain medium are pumped to the high energy level, and then the population inversion of the particles on the target transition energy level is achieved through spontaneous emission. 2) The target transition energy level that achieves population inversion generates a fluorescence signal of the target wavelength through spontaneous emission; the resonant cavity continuously amplifies the fluorescence signal of the target wavelength to form stimulated emission signal light of the target wavelength, which is used as the optical frequency standard signal output of the active optical clock of the chip. 3) The polarizing beam splitter (11) is used to combine the optical frequency standard signal and the comb light signal output by the microcavity optical comb (10) to generate a beat frequency optical signal; 4) The second thin-film photodetector (12) receives the beat frequency optical signal and converts it into a beat frequency electrical signal; 5) The digital frequency counter (13) measures the beat frequency electrical signal and processes it to output a clock signal, thereby realizing the chip's active optical clock.

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