Micro narrow-linewidth atom frequency-selecting Faraday laser based on microcavity frequency stabilization

Abstract

The invention discloses a micro narrow linewidth atom frequency-selecting Faraday laser based on microcavity frequency stabilization, which is characterized by comprising a Faraday laser, an electro-optical modulator, an echo wall microcavity module, a photoelectric detector, a signal generator and a servo loop feedback system, laser output by the Faraday laser is divided into two beams by the beam splitter, one beam is modulated by the electro-optical modulator and then is input to the echo wall microcavity module, and the other beam is output as frequency-stabilized laser; the electro-optical modulator is used for receiving a radio frequency driving signal of the signal generator and modulating the input laser; the echo wall microcavity module stabilizes the input laser frequency to an echo wall microcavity; the photoelectric detector is used for converting an optical signal output by the echo wall microcavity module into an electric signal and inputting the electric signal into the servo loop feedback system; and the servo loop feedback system controls the Faraday laser according to the input signal. The invention provides a laser light source which is narrow in linewidth, high in stability, low in cost and small in size.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, and in particular relates to a micro-cavity frequency stabilization-based miniature narrow-linewidth atomic frequency-selective Faraday laser and a realization method thereof. Background Art

[0002] Faraday laser uses Faraday atomic filter as frequency selection element, and the output wavelength automatically corresponds to the atomic transition wavelength, which can be used immediately. Compared with other semiconductor lasers, Faraday laser has strong anti-interference ability to changes in the driving current and operating temperature of the laser diode. By locking the frequency of Faraday laser, the laser frequency can be further stabilized to obtain a laser light source with narrower line width and higher frequency stability, thus gaining broad application prospects in the fields of precision measurement, quantum communication, precision spectroscopy and quantum sensing.

[0003] Pound-Drever-Hall (PDH) frequency stabilization is an active frequency locking technology and one of the best performing methods in the current laser frequency stabilization system. The traditional method is to use the optical interference effect in the cavity and radio frequency electronics technology to measure the frequency of the laser by injecting the output light of the laser into the ultra-stable Fabry-Pérot (FP) optical reference cavity, and feed the measurement result back to the laser to suppress the frequency deviation of the laser, thereby obtaining a narrow linewidth laser with high long-term stability. However, due to the large size of the cavity used in the traditional PDH frequency stabilization system, it is not easy to integrate, and the high-reflectivity cavity mirror is expensive and requires complex stabilization devices, it is still not widely used. Therefore, it is an urgent problem to realize a small integrated narrow linewidth laser frequency stabilization system with superior performance, simple system, low cost and easy handling.

[0004] At present, miniaturized optical cavities are in a stage of rapid development. The research and development of micro-cavities such as micro FP cavities, on-chip whispering gallery mode optical microcavities, and crystal whispering gallery optical microcavities have gradually matured. Among them, the whispering gallery mode microcavity (WGM) is small in size, excellent in performance, low in cost, and widely used. In the whispering gallery microcavity, different crystal materials have different absorption coefficients. The whispering gallery microcavity crystals currently include SiO2, Si, Si3N4, CaF2, MgF2, LiNbO3 and other different materials. The shape and size will also affect the optical mode field distribution of the microcavity, which includes different morphological structures such as microsphere cavity, microdisk cavity, microring core cavity and microring cavity. Based on different research needs, the whispering gallery microcavity with corresponding crystal material and morphological structure is selected.

[0005] The Faraday laser is locked to the whispering gallery microcavity through the PDH frequency stabilization technology to realize a miniature narrow-linewidth atomic frequency-selective Faraday laser system based on microcavity frequency stabilization. This solves the problems of poor anti-interference ability of the laser, complex reference cavity system, high cost, large system size and difficulty in transportation in the traditional PDH frequency stabilization system. It can be used as a narrow-linewidth, high-stability, low-cost, miniaturized and easy-to-carry laser light source. Summary of the invention

[0006] In order to realize a micro laser system with narrow line width and high stability, the present invention proposes a micro narrow line width atomic frequency selective Faraday laser system based on micro cavity frequency stabilization and an implementation method. The present invention selects a Faraday laser with strong anti-interference as the laser light source and a whispering gallery micro cavity as the frequency reference, which reduces the complexity of the system, saves experimental costs, and increases the robustness of the system. Therefore, it can be used as a laser light source with narrow line width, high stability, low cost, miniaturization and easy to carry.

[0007] The present invention uses a high-performance, miniaturized microcavity as a laser frequency reference and achieves frequency stabilization, which can effectively reduce the size of the system and reduce the experimental cost; the ready-to-use Faraday laser is selected as the laser light source, and the microcavity frequency stabilization is used to realize a miniature narrow-linewidth atomic frequency-selective Faraday laser system, which can not only improve the laser frequency stability and narrow the laser linewidth, but also the output laser wavelength automatically corresponds to the quantum transition, which is the preferred narrow-linewidth light source in the field of quantum precision measurement. This patent proposes the use of an atomic frequency-selective Faraday laser as the local oscillator light, and uses a microcavity PDH frequency stabilization to realize a miniature narrow-linewidth atomic frequency-selective Faraday laser. This is the first time that this solution has the advantages of narrow linewidth, small size, and wavelength automatically corresponding to quantum transitions, and is an advantageous light source in the field of quantum precision measurement.

[0008] The technical solution of the present invention is:

[0009] A micro-narrow linewidth atomic frequency-selective Faraday laser based on micro-cavity frequency stabilization, characterized in that it comprises a Faraday laser 1, an electro-optic modulator 3, a whispering gallery micro-cavity module 5, a photodetector 6, a signal generator 9 and a servo loop feedback system;

[0010] The laser output by the Faraday laser 1 is divided into two beams by a beam splitter, one beam is modulated by the electro-optic modulator 3 and then input into the whispering gallery microcavity module 5, and the other beam is output as a frequency-stabilized laser;

[0011] The electro-optic modulator 3 is connected to the signal generator 9 and is used to modulate the incident laser according to the radio frequency driving signal input by the signal generator 9;

[0012] The whispering gallery microcavity module 5 stabilizes the input laser frequency to the whispering gallery microcavity;

[0013] The photodetector 6 is used to convert the optical signal output by the whispering gallery microcavity module 5 into an electrical signal and input it into the servo loop feedback system;

[0014] The servo loop feedback system controls the Faraday lasers 1 respectively according to the input signal.

[0015] Furthermore, the laser output by the atomic frequency-selective Faraday laser is sequentially divided into two beams by the optical isolator 2 and the polarization-maintaining fiber beam splitter.

[0016] Furthermore, the servo loop feedback system includes an amplifier 7, a mixer 8, a low-pass filter 10 and a proportional-integral-differential controller 11; the signal generator 9 is used to generate a driving signal input to the radio frequency port of the electro-optical modulator 3, and an intrinsic signal with the same frequency as the driving signal is input to the mixer 8; the electro-optical modulator 3 modulates the input laser according to the driving signal, and then the polarization state of the light is adjusted by a polarization controller 4 before entering the whispering gallery microcavity module 5; the electrical signal output by the photodetector 6 is amplified by the amplifier 7 and then input to the mixer 8; the mixer 8 is used to mix the input amplified electrical signal with the intrinsic signal generated by the signal generator to demodulate the error signal, and then process it in turn through the low-pass filter 10 and the proportional-integral-differential controller 11 to generate a feedback signal and input it to the Faraday laser 1, so as to realize PDH frequency stabilization of the Faraday laser 1 based on the whispering gallery microcavity; wherein the intrinsic signal has the same frequency as the driving signal.

[0017] Furthermore, the proportional-integral-differential controller 11 divides the feedback signal into three paths to respectively feedback-control the fast reverse current, slow reverse current and piezoelectric ceramic of the Faraday laser 1 to adjust the resonant cavity length of the Faraday laser 1, thereby controlling the laser frequency of the Faraday laser 1.

[0018] Furthermore, the magnetic field strength of the atomic gas chamber of the Faraday laser is 3500 Gs and the temperature is between 70-80°C.

[0019] Furthermore, the whispering gallery microcavity crystal material of the whispering gallery microcavity module 5 is MgF2, SiO2, Si, Si3N4, CaF2 or LiNbO3.

[0020] Furthermore, the whispering gallery microcavity of the whispering gallery microcavity module 5 is a micro-disk cavity, a micro-sphere cavity, a micro-ring core cavity or a micro-ring cavity.

[0021] Furthermore, the signal output by the photodetector 6 is input to the amplifier 7 via a high-pass filter, and the high-pass filter is used to allow high-frequency signals in the input signal to pass through, thereby suppressing low-frequency noise.

[0022] Furthermore, the output frequency of the Faraday laser 1 is 766 nm, 770 nm, 780 nm, 795 nm or 852 nm.

[0023] The output frequency of the Faraday laser of the present invention corresponds to the central wavelength of the atomic transition spectrum of the frequency-selective element Faraday atomic filter, and the laser wavelengths include 766nm, 770nm, 780nm, 795nm, 852nm, etc. The reference cavity is a whispering gallery mode crystal microcavity, and the PDH frequency stabilization technology is used to stabilize the output laser frequency of the laser to the crystal microcavity, suppress the laser frequency drift, and realize a narrow linewidth laser of the Hz order.

[0024] The micro-cavity frequency stabilization-based miniature narrow-linewidth atom-selective Faraday laser system structurally comprises: an atom-selective Faraday laser, a PDH frequency stabilization system based on a whispering gallery microcavity, and a servo loop feedback system.

[0025] The atomic frequency-selective Faraday laser structurally includes: a laser diode driving power supply, a laser diode coated with an anti-reflection film, a collimating lens, a Faraday atomic filter, a high-reflection cavity mirror, and a piezoelectric ceramic. Among them, the Faraday atomic filter includes: an atomic gas chamber, a permanent magnet, a temperature control module, a first polarization beam splitter prism, and a second polarization beam splitter prism. The light emitted by the laser diode coated with an anti-reflection film under the driving power supply is collimated by the collimating lens and enters the Faraday atomic filter. After passing through the first polarization beam splitter prism, it enters the atomic gas chamber under a uniform magnetic field. The temperature of the atomic gas chamber is adjusted by the temperature control module. Under the Faraday optical rotation effect, the polarization direction of the light passing through the atomic gas chamber rotates. Only the light with a polarization direction rotated by 90° can pass through the second polarization beam splitter prism, thereby performing frequency selection. The reflected light passing through the second polarization beam splitter prism hits the high-reflection cavity mirror and then returns to the laser diode, forming a resonant cavity with the front end face of the laser diode. By adjusting the piezoelectric ceramic installed behind the high-reflection cavity mirror, the cavity length of the laser resonant cavity is adjusted, thereby realizing laser frequency adjustment. The transmitted light through the second polarization beam splitter is used as the output laser. After passing through the optical isolator, the output laser is coupled to the optical fiber beam splitter through the optical fiber coupling head and split into two beams, one of which is directly output for other experiments and the other is used for subsequent PDH frequency stabilization.

[0026] The PDH frequency stabilization system based on the whispering gallery microcavity includes: a signal generator, an electro-optic modulator, a polarization controller, a microcavity module, a photodetector, an amplifier, a mixer, a low-pass filter, and a proportional-integral-differential controller.

[0027] The signal generator generates an RF signal which is input into the electro-optic modulator. After the stabilized frequency laser enters the electro-optic modulator, sidebands are modulated on both sides. The modulated stabilized frequency laser passes through the polarization controller and enters the coupled whispering gallery microcavity module. A part of the laser in the scanning state will be coupled into the microcavity. Finally, the laser output enters the photodetector and is converted from an optical signal into an electrical signal to realize photoelectric conversion. The electrical signal coming out of the detector is divided into two paths. One path is connected to an oscilloscope for monitoring, where obvious resonant spectrum lines can be seen, and the other path enters the servo feedback circuit system.

[0028] After the electrical signal output by the photodetector enters the servo feedback circuit system, it is first filtered out with a filter to remove some noise, and then amplified by an amplifier. The amplified electrical signal is mixed with the local oscillator signal generated by the signal generator through a mixer, where the local oscillator signal entering the mixer and the radio frequency signal of the electro-optical modulator are both generated by the signal generator and have the same signal frequency. The mixed electrical signal is demodulated to obtain an error signal. The error signal outputs a feedback signal through a proportional-integral-differential controller. The servo loop feedback system divides the feedback signal into three paths and feeds it back to the laser's fast reverse current, slow reverse current and piezoelectric ceramics to adjust the cavity length of the laser resonant cavity, thereby controlling the laser frequency.

[0029] Furthermore, the temperature control module in the laser diode driving power supply includes a thermistor, a semiconductor cooler TEC and a temperature control feedback circuit, which can accurately control the laser diode.

[0030] Furthermore, the output laser of the Faraday laser is determined by the transmission spectrum of the Faraday atomic filter, and the transmission spectrum changes with the temperature and magnetic field strength of the atomic gas chamber. Through a large number of experimental verifications, the stable 780nm laser output, the magnetic field strength of the atomic gas chamber is 3500Gs, and the gas chamber temperature is between 70-80℃.

[0031] Furthermore, the first polarization beam splitter prism and the second polarization beam splitter prism of the Faraday atomic filter are orthogonal to each other.

[0032] Furthermore, a high-pass filter is placed after the photodetector to allow high-frequency signals in the signal to pass through, thereby suppressing low-frequency noise.

[0033] Furthermore, a polarization controller is used to change the polarization state of light entering the whispering gallery microcavity.

[0034] Furthermore, the atomic frequency-selective Faraday laser is an L-shaped resonant cavity of 15.6 cm, and the size of the laser can be adjusted by changing the length of the resonant cavity and using a partially reflecting cavity mirror to convert the L-shaped resonant cavity into a straight cavity.

[0035] Furthermore, the high-reflection cavity mirror used in the atomic frequency-selective Faraday laser can be a corner-cone reflector to further improve the laser frequency stability.

[0036] Furthermore, the output wavelength of the atomic frequency-selective Faraday laser is 780nm. By changing the optically active medium in the Faraday atomic filter, Faraday lasers with different wavelengths such as 770nm, 776nm, 795nm, 852nm, and 894nm can be realized as a PDH frequency-stabilized light source.

[0037] Furthermore, whispering gallery microcavities composed of different crystal materials such as SiO2, Si, Si3N4, CaF2, MgF2, and LiNbO3 are used as optical reference cavities.

[0038] Furthermore, whispering gallery microcavities of different morphological structures, shapes and sizes, such as microsphere cavity, microdisk cavity, microring core cavity and microring cavity, are used as optical reference cavities.

[0039] Furthermore, the optical cavity is a whispering gallery mode microcavity, and other forms of microcavities such as a micro FP cavity, an on-chip whispering gallery mode optical microcavity, etc. can also be used as a reference cavity.

[0040] Compared with the prior art, the present invention has the following positive effects:

[0041] Compared with the prior art, the present invention is the first to use atomic frequency-selective Faraday lasers and whispering gallery microcavities for PDH frequency stabilization. The first laser light source selected is an atomic frequency-selective Faraday laser. Compared with other semiconductor lasers, the laser wavelength of the Faraday laser automatically corresponds to quantum transitions, which is ready for use and highly robust. The external cavity is combined with a narrow-bandwidth atomic filter for frequency selection, which makes the Faraday laser have a narrow linewidth and high frequency stability. In addition, for the first time, the Faraday laser is stabilized on a high-precision whispering gallery microcavity through PDH frequency stabilization technology. Compared with traditional ultra-high-precision optical resonant cavities, the system has simple results, low cost, and superior performance. The frequency-selective Faraday laser based on microcavity frequency stabilization further narrows the linewidth of the Faraday laser, improves frequency stability, and realizes a high-stability, small-scale integrated narrow-linewidth laser light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the structure of a Faraday laser that selects frequencies for atoms.

[0043] Figure 2 Schematic diagram of the structure of the atom-selective Faraday laser based on microcavity PDH frequency stabilization.

[0044] Figure numerals: 1-Faraday laser; 2-optical isolator; 3-electro-optic modulator; 4-polarization controller; 5-whispering gallery microcavity module; 6-photodetector; 7-amplifier; 8-mixer; 9-signal generator; 10-low-pass filter; 11-proportional integral differential controller; 01-laser diode driving power supply; 02-laser diode coated with anti-reflection film; 03-collimating lens; 04-first polarization beam splitter prism; 05-atomic gas chamber; 06-permanent magnet; 07-temperature control module; 08-second polarization beam splitter prism; 09-high reflection cavity mirror; 010-piezoelectric ceramics. DETAILED DESCRIPTION

[0045] In order to make the objectives, features and advantages of the technical solutions of the present invention more clear, specific implementation schemes are now described in detail with reference to the accompanying drawings.

[0046] The small integrated narrow-linewidth atom frequency-selective Faraday laser based on microcavity frequency stabilization mainly comprises: an atom frequency-selective Faraday laser system, a PDH frequency stabilization system based on microcavity and a servo circuit feedback system.

[0047] Example 1

[0048] Atom-selective Faraday lasers, see Figure 1 The laser structure includes a laser diode driving power supply 01, a laser diode coated with an anti-reflection film 02, a collimating lens 03, a first polarization beam splitter prism 04, an atomic gas chamber 05, a permanent magnet 06, a temperature control module 07, a second polarization beam splitter prism 08, a high-reflection cavity mirror 09, and a piezoelectric ceramic 010; the implementation steps are as follows:

[0049] Step 1: When driven by the laser diode driving power supply 01, the anti-reflection film-coated laser diode 02 emits light with a wide wavelength range and a large divergence angle. The laser divergence angle is adjusted by the collimating lens 03, and the light spot is calibrated before entering the Faraday atomic filter.

[0050] Step 2: The light entering the Faraday atomic filter passes horizontally through the atomic gas chamber 05 in the permanent magnet 06 after passing through the first polarization beam splitter prism 04. The temperature of the atomic gas chamber 05 is adjusted by the temperature control module 07. Under the Faraday optical rotation effect, the polarization direction of the light passing through the atomic gas chamber 05 rotates. Only the light with a polarization direction rotated by 90° can pass through the second polarization beam splitter prism 08 for frequency selection. At a specific magnetic field strength and temperature of the atomic gas chamber, the transmission spectrum of the Faraday atomic filter is optimized based on the Faraday optical rotation effect. When the collimated laser passes through the Faraday atomic filter, it accurately corresponds to the cesium atomic transition wavelength.

[0051] Step 3: The reflected light from the second polarization beam splitter prism 08 hits the high-reflection cavity mirror 09 with a reflectivity of >99.98% and then returns to the anti-reflection film-coated laser diode 02 to form a resonant cavity with its front end face. By adjusting the piezoelectric ceramic 010 installed behind the high-reflection cavity mirror 09, the length of the laser resonant cavity is adjusted, thereby adjusting the laser frequency and finally outputting a specific laser frequency. The transmitted light from the second polarization beam splitter prism 08 is used as the output laser.

[0052] Example 2

[0053] PDH frequency stabilization system based on whispering gallery microcavity, see Figure 2 The main structure of the system includes a Faraday laser 1, an optical isolator 2, an electro-optic modulator 3, a polarization controller 4, a whispering gallery microcavity module 5, a photodetector 6, an amplifier 7, a mixer 8, a signal generator 9, a low-pass filter 10, and a proportional-integral-differential controller 11.

[0054] The frequency stabilization steps are as follows:

[0055] Step 1: The output laser of Faraday laser 1 passes through optical isolator 2, which can make the optical path transmission direction unidirectional, reduce the influence of the subsequent optical path on the laser output light, and improve the signal-to-noise ratio. The spatial light is coupled to the 50:50 polarization-maintaining fiber beam splitter through the fiber coupling head, and the laser is divided into two beams, one of which is used for testing and the other is used as a frequency-stabilized light source based on microcavity PDH.

[0056] Step 2: The electro-optic modulator 3 is driven by the RF signal generated by the signal generator 9. After the stabilized laser passes through the electro-optic modulator 3, sideband signals are modulated on both sides. The distance and size of the sideband signals from the stabilized laser are determined by the frequency and amplitude of the RF signal. The modulated stabilized laser passes through the polarization controller 4 and enters the whispering gallery microcavity module 5. The polarization state of the light entering the whispering gallery microcavity is changed by adjusting the polarization controller.

[0057] Step 3: A large part of the laser light of the Faraday laser in the scanning state is coupled to the whispering gallery microcavity module 5, and finally the laser output enters the photodetector 6, where the optical signal is converted into an electrical signal to realize photoelectric conversion. The electrical signal from the photodetector 6 is then divided into two paths, one of which is connected to an oscilloscope for monitoring, where an obvious resonant spectrum can be seen, and the other enters the servo feedback circuit system.

[0058] Step 4: After the electrical signal output by the photodetector 6 enters the servo feedback circuit system, it is amplified by the amplifier 7. The amplified electrical signal is mixed with the local oscillator signal by the mixer 8. The local oscillator signal entering the mixer and the radio frequency signal of the electro-optical modulator 3 are both generated by the signal generator 9 and have the same frequency.

[0059] Step 5: The mixer 8 mixes the modulated frequency-stabilized laser with the intrinsic signal to achieve frequency conversion, obtain an error signal, and pass it through a low-pass filter 10 to suppress high-frequency signals.

[0060] The proportional-integral-differential controller 11 outputs a feedback signal through the input error signal, and divides the feedback signal into three paths, which are respectively fed back to the fast reverse current, slow reverse current and piezoelectric ceramic of the laser to adjust the cavity length of the laser resonant cavity, thereby controlling the laser frequency. Finally, the atomic frequency-selective Faraday laser based on the PDH frequency stabilization of the whispering gallery microcavity is realized.

[0061] Furthermore, the temperature control module in the laser diode driving power supply includes a thermistor, a semiconductor cooler TEC and a temperature control feedback circuit, which can accurately control the laser diode.

[0062] Furthermore, the output laser of the Faraday laser is determined by the transmission spectrum of the Faraday atomic filter, and the transmission spectrum changes with the temperature and magnetic field strength of the atomic gas chamber. Through a large number of experimental verifications, the stable 780nm laser output, the magnetic field strength of the atomic gas chamber is 3500Gs, and the gas chamber temperature is between 70-80℃.

[0063] Furthermore, the first polarization beam splitter prism and the second polarization beam splitter prism of the Faraday atomic filter are orthogonal to each other.

[0064] Furthermore, a high-pass filter is placed after the photodetector to allow high-frequency signals in the signal to pass through, thereby suppressing low-frequency noise.

[0065] Furthermore, the polarization controller can adjust the extinction ratio of the laser coupled into the whispering gallery microcavity.

[0066] Furthermore, the atomic frequency-selective Faraday laser is an L-shaped resonant cavity of 15.6 cm, and the size of the laser can be adjusted by changing the length of the resonant cavity and using a partially reflecting cavity mirror to convert the L-shaped resonant cavity into a straight cavity.

[0067] Furthermore, the high-reflection cavity reflector used in the atomic frequency-selective Faraday laser can be a corner cube reflector to further improve the laser frequency stability.

[0068] Furthermore, the output wavelength of the atomic frequency-selective Faraday laser is 780nm. By changing the optically active medium in the Faraday atomic filter, Faraday lasers with different wavelengths such as 770nm, 776nm, 795nm, 852nm, and 894nm can be realized as a PDH frequency-stabilized light source.

[0069] Furthermore, the whispering gallery microcavity crystal material is MgF2. Whispering gallery microcavities made of different crystal materials such as SiO2, Si, Si3N4, CaF2, LiNbO3, etc. can all be used as optical reference cavities.

[0070] Furthermore, the whispering gallery microcavity is a microdisk cavity, a microsphere cavity, a microring core cavity, a microring cavity, and other whispering gallery microcavities of different morphological structures, shapes and sizes can all be used as optical reference cavities.

[0071] Furthermore, the optical cavity is a whispering gallery mode microcavity, and other forms of microcavities such as a micro FP cavity, an on-chip whispering gallery mode optical microcavity, etc. can also be used as a reference cavity.

[0072] The present invention proposes a miniature narrow-linewidth atomic frequency-selective Faraday laser based on microcavity frequency stabilization. The Faraday atomic filter is used for frequency selection, and the laser wavelength automatically corresponds to the quantum transition, which is ready for use. Compared with other semiconductor lasers, the Faraday laser has a strong anti-interference ability to the output laser frequency due to external vibrations, temperature changes and current fluctuations. A micro-optical cavity is selected as the frequency reference, and the PDH frequency stabilization technology is used to lock the Faraday laser to the microcavity, thereby realizing a small integrated narrow-linewidth laser frequency stabilization system with superior performance, simple system, low cost and easy handling. Those skilled in the art should fully understand that, without departing from the technical principles of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A micro-narrow linewidth atomic frequency-selective Faraday laser based on micro-cavity frequency stabilization, characterized in that: It comprises a Faraday laser (1), an electro-optic modulator (3), a whispering gallery microcavity module (5), a photodetector (6), a signal generator (9) and a servo loop feedback system; The laser light output by the Faraday laser (1) is split into two beams by a beam splitter, one beam is modulated by the electro-optic modulator (3) and then input into the whispering gallery microcavity module (5), and the other beam is output as a frequency-stabilized laser light; The electro-optic modulator (3) is connected to the signal generator (9) and is used to modulate the incident laser according to the radio frequency driving signal input by the signal generator (9); The whispering gallery microcavity module (5) stabilizes the input laser frequency to the whispering gallery microcavity; The photoelectric detector (6) is used to convert the optical signal output by the whispering gallery microcavity module (5) into an electrical signal and input it into the servo loop feedback system; The servo loop feedback system controls the Faraday laser (1) respectively according to the input signal.

2. The miniature narrow linewidth atomic frequency-selective Faraday laser according to claim 1, characterized in that: The laser light outputted by the atomic frequency-selective Faraday laser is sequentially divided into two beams by an optical isolator (2) and a polarization-maintaining optical fiber beam splitter.

3. The miniature narrow linewidth atomic frequency-selective Faraday laser according to claim 2, characterized in that: The servo loop feedback system comprises an amplifier (7), a mixer (8), a low-pass filter (10) and a proportional-integral-differential controller (11); The signal generator (9) is used to generate a driving signal which is input to the radio frequency port of the electro-optic modulator (3), and an eigensignal with the same frequency as the driving signal which is input to the mixer (8); The electro-optic modulator (3) modulates the input laser light according to the driving signal, and the laser light passes through a polarization controller (4) to adjust the polarization state of the light before entering the whispering gallery microcavity module (5); The electrical signal output by the photodetector (6) is amplified by the amplifier (7) and then input into the mixer (8); The mixer (8) is used to mix the input amplified electrical signal with the intrinsic signal generated by the signal generator to demodulate the error signal, and then process it in sequence through the low-pass filter (10) and the proportional-integral-differential controller (11) to generate a feedback signal which is input into the Faraday laser (1), thereby achieving PDH frequency stabilization of the Faraday laser (1) based on the whispering gallery microcavity; wherein the intrinsic signal has the same frequency as the drive signal.

4. The miniature narrow linewidth atomic frequency-selective Faraday laser according to claim 3, characterized in that: The proportional-integral-differential controller (11) divides the feedback signal into three paths to respectively feedback-control the fast reverse current, the slow reverse current and the piezoelectric ceramic of the Faraday laser (1) to adjust the cavity length of the resonant cavity of the Faraday laser (1), thereby controlling the laser frequency of the Faraday laser (1).

5. The miniature narrow linewidth atomic frequency-selective Faraday laser according to claim 1, 2 or 3, characterized in that: The magnetic field strength of the atomic gas chamber of the Faraday laser is 3500 Gs and the temperature is between 70-80°C.

6. The miniature narrow linewidth atomic frequency-selective Faraday laser according to claim 1, 2 or 3, characterized in that: The whispering gallery microcavity crystal material of the whispering gallery microcavity module (5) is MgF2, SiO2, Si, Si3N4, CaF2 or LiNbO3.

7. The miniature narrow linewidth atomic frequency-selective Faraday laser according to claim 1, 2 or 3, characterized in that: The whispering gallery microcavity of the whispering gallery microcavity module (5) is a microdisk cavity, a microsphere cavity, a microring core cavity or a microring cavity.

8. The miniature narrow linewidth atomic frequency-selective Faraday laser according to claim 1, characterized in that: The signal output by the photodetector (6) is input into the amplifier (7) via a high-pass filter. The high-pass filter is used to allow high-frequency signals in the input signal to pass through, thereby suppressing low-frequency noise.

9. The miniature narrow linewidth atomic frequency-selective Faraday laser according to claim 1, characterized in that: The output frequency of the Faraday laser (1) is 766 nm, 770 nm, 780 nm, 795 nm or 852 nm.

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