Miniature single-frequency faraday laser with ultra-large tunable range and implementation method thereof

Abstract

This invention discloses a miniature single-frequency Faraday laser with an ultra-wide tunable range and its implementation method, comprising: a laser diode coated with an antireflection film as a seed source for the Faraday laser; a collimation module including a collimating lens and a corresponding fixing structure; a miniature Faraday atom filter to filter the laser emitted from the laser diode, the final output laser being determined by the transmission spectrum of the filter; a reflecting cavity mirror with a preset reflection ratio to reflect the filtered laser back into the resonant cavity, forming oscillations and generating stable laser light, the remaining laser light being transmitted out of the laser through the reflecting cavity mirror; and a temperature control module consisting of a TEC semiconductor cooler and a temperature feedback control circuit for adjusting the operating temperature of the laser diode. The laser designed in this invention is much smaller than that of mainstream Faraday lasers, has better mechanical stability and frequency stability of the output laser, and is more portable, enabling it to play an important role in laser technology, optical communication, optical networks, quantum communication, and other fields.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and in particular to a miniature single-frequency Faraday laser with an ultra-large tunable range and its implementation method. Background Technology

[0002] Under the influence of an external magnetic field, the atomic transition spectral lines in the alkali metal atom gas cell are induced to split, resulting in a difference in refractive index between the left-handed and right-handed circularly polarized light in the incident laser after passing through the atom gas cell. Therefore, a phase difference exists between the left-handed and right-handed circularly polarized light after passing through the gas cell, causing a rotation of the polarization state of the emitted laser; this is the Faraday rotation effect. Based on this effect, the Faraday anomalous dispersion atomic filter has advantages such as narrow bandwidth, high transmittance, and insensitivity to ambient temperature, and has been widely used for laser frequency selection since its inception.

[0003] External cavity semiconductor lasers using Faraday atom filters as frequency selection devices exhibit excellent immunity to changes in the operating current and temperature of the laser diode. For a Faraday laser that is already functioning normally, significant changes to the laser diode's operating current and temperature will not cause a large fluctuation in the output laser frequency, as long as the operating current remains above the threshold. For a Faraday laser that has been properly tuned, it can still operate near the target wavelength after prolonged use. Therefore, using Faraday atom filters as external cavity frequency selection devices can improve the problems of severe mode hopping and significant temperature drift in semiconductor laser diodes, enabling the creation of high-performance lasers with stable output laser frequency, strong anti-interference capabilities, and long-term stable operation. This method significantly improves laser performance at a low cost, providing a unique solution to the current situation where high-performance lasers cannot be built using low-performance semiconductor laser diodes.

[0004] When a Faraday laser made of pure alkali metal atomic gas cells is in operation, it cannot guarantee single-frequency laser output; furthermore, the transmission bandwidth of pure atomic filters is narrow, and the Faraday laser made from this is relatively weak in its ability to resist interference from changes in the operating current and temperature of the laser diode.

[0005] Filling the alkali metal atom gas chamber with a buffer gas can effectively improve the above problems, enabling the Faraday laser to achieve single-frequency output and broaden the transmission spectrum bandwidth of the atomic filter, thereby enhancing the anti-interference capability of the Faraday laser.

[0006] Currently, the mainstream Faraday lasers filled with buffer gas have a cavity length of 60 cm. On the one hand, their corresponding free spectral range is 250 MHz. Therefore, when using piezoelectric ceramics to change the cavity length to sweep the laser frequency, the sweep range is small, which cannot be applied to a series of scientific research and engineering applications that have strict requirements for the sweep range, such as detecting the transmission spectrum of filters. On the other hand, large cavity length lasers also have problems such as large size, relatively poor portability and mechanical stability. Summary of the Invention

[0007] This invention provides a miniature single-frequency Faraday laser with an ultra-wide tunable range and its implementation method. The invention provides a method for realizing a miniature Faraday atom filter filled with high-pressure buffer gas, a laser diode with antireflection coating and collimation, beam expansion, and temperature control modules, and a reflecting cavity mirror equipped with piezoelectric ceramics. The invention also provides a method for using this laser to stably output single-frequency laser light and perform wide-range laser tuning, as detailed below:

[0008] A miniature single-frequency Faraday laser with an ultra-wide tuning range, the Faraday laser comprising:

[0009] Laser diodes coated with antireflective coatings, as seed sources for Faraday lasers, have a wide range of emission wavelengths and a large divergence angle of the emitted laser.

[0010] The collimation module, comprising a collimating lens and a corresponding fixing structure, is used to collimate the laser diode;

[0011] A miniature Faraday atom filter filters the laser light emitted from a laser diode. The output laser light of a miniature Faraday laser is determined by the transmission spectrum of the miniature Faraday atom filter.

[0012] A reflective cavity mirror with 80% reflectivity reflects the laser light filtered by the atomic filter back into the resonant cavity, forming oscillations and generating stable laser light. 20% of the laser light will be transmitted out of the laser from the reflective cavity mirror. Therefore, the reflective cavity mirror is also the output window of the miniature Faraday laser.

[0013] The integrated mechanical structure of the laser mainly includes: a laser base, four side plates and a cover plate, which are used to fix the components in the laser and assemble the various components into a whole.

[0014] Furthermore, a temperature control module consisting of a TEC semiconductor cooler and a temperature feedback control circuit is used to adjust the operating temperature of the laser diode, with a temperature control accuracy of 0.1 degrees Celsius; a collimation module is used to collimate the laser emitted from the laser diode, reducing the divergence angle of the emitted laser to 0.1 degrees.

[0015] Furthermore, the miniature Faraday atom filter includes:

[0016] The alkali metal atom gas cell is a glass gas cell with a length of 3 to 10 mm, which is filled with alkali metal atoms and a buffer gas for transmission spectrum broadening and shaping. The type of buffer gas is generally an inert gas, such as xenon or argon. The buffer gas pressure is preferably 20 to 50 Torr.

[0017] The magnetic field generator is a specially designed ring-shaped permanent magnet that can generate a magnetic field with a uniformity of over 95% along the laser transmission direction in an atomic gas chamber. By designing different permanent magnet sizes, the magnetic field strength can be varied from 100 to 3500 Gauss, with the preferred magnetic field strength being 1000 to 2000 Gauss.

[0018] The temperature control module monitors and provides feedback control of the temperature of the alkali metal atom gas chamber. The temperature control range is 30-200 degrees Celsius, the temperature control accuracy is 0.01 degrees Celsius, and the preferred temperature is 60-120 degrees Celsius.

[0019] The polarization filter module consists of two polarization splitters with orthogonal polarization directions, located on both sides of the alkali metal atom gas cell, to filter laser light whose polarization direction rotates under the action of a magnetic field.

[0020] Furthermore, a piezoelectric ceramic is attached to the back of the reflecting cavity mirror, which allows the laser cavity length to be changed during laser operation, thereby achieving frequency adjustment of the output laser. This process is known as the laser's frequency sweep process. The piezoelectric ceramic has a stroke of 3.3 μm, and the frequency sweep range is related to the laser cavity length and the operating wavelength.

[0021] Furthermore, a reflective cavity mirror with piezoelectric ceramic attached is mounted on a mirror mount. By changing the position of the mirror mount, the cavity length of the laser can be adjusted. The cavity length range of the miniature Faraday laser is 10–80 mm, corresponding to a free spectral range of 15–1.875 GHz.

[0022] Secondly, a method for realizing a miniature single-frequency Faraday laser with an ultra-large tuning range, the method comprising:

[0023] A laser diode with a temperature control module and a collimation module is mounted on a laser base. The position of the lens in the collimation module is adjusted to minimize the divergence angle of the laser emitted from the collimation module.

[0024] A miniature Faraday atom filter, equipped with a temperature control module and a magnetic field generator, is mounted on the laser base. The polarization directions of the two polarizers are set to be parallel, and the temperature control module is turned off.

[0025] The mirror mount containing the reflective cavity mirror and piezoelectric ceramic is assembled onto the laser base. By adjusting the pitch of the mirror mount, the pitch of the reflective cavity mirror is changed, so that the laser reflected at the cavity mirror returns along its original path, maximizing the feedback of the resonant cavity and causing the laser to oscillate.

[0026] When the polarizer of the rotating atomic filter is placed close to the mirror of the reflecting cavity, its polarization direction is made orthogonal to that of another polarizer. At this time, the loss of the resonant cavity is too large, and the laser cannot start oscillating.

[0027] Turn on the temperature control module of the atomic filter and raise the temperature to a suitable level. The polarization direction of the laser near the atomic transition frequency rotates by 90° under the Faraday rotation effect, so that the laser near this frequency can be emitted from the orthogonal polarizer. The resonant cavity loss decreases, the laser restarts, and the frequency of the output laser is near the atomic transition frequency.

[0028] By changing the voltage across the piezoelectric ceramic, its thickness can be altered, thereby changing the cavity length of the laser and thus altering its output frequency. This method is known as laser tuning for Faraday lasers. The tunable range of a laser is determined by the smaller of the laser's free spectral range and the transmission bandwidth of the atomic filter. If the free spectral range is large, during laser tuning, it will be observed that when the operating frequency exceeds the transmission bandwidth of the atomic filter, the cavity loss of the laser becomes too high, causing the laser to shut down. Therefore, the tunable range is limited by the transmission bandwidth of the atomic filter. Conversely, if the transmission bandwidth of the atomic filter is large, when the operating frequency exceeds one boundary of the free spectral range, the operating frequency will immediately jump to the other boundary of the free spectral range.

[0029] The beneficial effects of the technical solution provided by this invention are:

[0030] 1. This invention reduces the cavity length of the Faraday laser to a minimum of 1 / 60 of the mainstream size, and the volume of the laser is also much smaller than that of the mainstream Faraday laser. It has better mechanical stability and frequency stability of output laser, and better portability. It can play an important role in laser technology, optical communication, optical network, quantum communication and other fields.

[0031] 2. The cavity length of the miniature Faraday laser of the present invention can be as small as 10 mm, corresponding to a free spectral range of 15 GHz, which is greater than the transmission bandwidth of conventional Faraday atomic filters. This ensures that only one longitudinal mode exists within the transmission spectral bandwidth of the atomic filter, achieving stable single-frequency output and preventing dual-frequency output.

[0032] 3. This invention significantly improves the transmission bandwidth of the micro Faraday atom filter by filling the atomic gas chamber with a high-pressure buffer gas, making it match the free spectral range of the micro Faraday laser. This increases the tunable range of the Faraday laser from 250MHz to 15GHz, greatly expanding the application scenarios of the Faraday laser. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a miniature Faraday laser.

[0034] The components include: 1. a laser diode with a temperature control module; 2. a collimating lens; 3. a miniature Faraday atom filter; 4. a reflecting cavity mirror; and 5. piezoelectric ceramics. The arrows in the diagram indicate the direction of the magnetic field, and the thick black line represents the laser transmission path.

[0035] Figure 2 The transmission spectrum of an atomic filter filled with high-pressure buffer gas when the cavity length is 1 cm;

[0036] Figure 3 The transmission spectrum of an atomic filter filled with high-pressure buffer gas when the cavity length is 60cm;

[0037] Figure 4 This is a flowchart illustrating the implementation and tuning method of a miniature Faraday laser. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below.

[0039] Example 1

[0040] A miniature Faraday laser, see Figure 1 The Faraday laser includes:

[0041] A laser diode 1 with an antireflection coating and a temperature control module is capable of exciting wavelengths in the range of 830-880 nm, operating at a temperature of 15–40 degrees Celsius, preferably with a maximum operating current of 200 mA and a corresponding maximum output power of 100 mW. The reflectivity of the window with the antireflection coating is preferably 1 × 10⁻⁶. -4 To prevent the laser diode from spontaneously generating an internal cavity mode, which could affect the laser's output performance, the fast-axis divergence angle of the emitted laser is 14-30°, and the slow-axis divergence angle is 7-10°. A semiconductor cooler combined with a temperature control module is used to control the temperature of the laser diode, with an optimal accuracy of 0.1 degrees Celsius.

[0042] A collimating lens 2, fixed in a sleeve, is used for collimating and expanding the laser beam. The collimated laser divergence angle is preferably 0.1°, and the spot diameter is preferably 2 mm. The distance between the end face of the collimating lens and the emitting end face of the laser diode is preferably 4.57 mm; therefore, the cavity length of the miniature Faraday laser must be greater than 4.57 mm.

[0043] A miniature Faraday atom filter 3 mainly consists of an alkali metal atom gas cell filled with a buffer gas and a polarizer with a preferred thickness of 0.22 mm. The arrows on the polarizers indicate their polarization directions, and the two polarizers are orthogonal to each other. Both polarizers are coated with an antireflection film, preferably with a transmittance greater than 91.3% and an extinction ratio greater than 10000:1. The arrows in the figure represent the direction of the magnetic field B, the magnitude of which can vary in the range of 100–2000 Gauss, preferably 800–1200 Gauss. The atom gas cell also includes a temperature control module, which can achieve temperature control with an accuracy of 0.01 degrees Celsius.

[0044] A reflecting cavity mirror 4 is preferably configured with a transmittance-to-reflection ratio of 8:2, meaning that 80% of the laser light is reflected back into the resonant cavity at the end face of the cavity mirror, and 20% of the laser light passes through the cavity mirror 4, thus achieving laser emission. The cavity length of the laser is the distance from the emitting end face of the laser diode 1 to the emitting end face of the cavity mirror 4.

[0045] A piezoelectric ceramic 5, assembled with a reflecting cavity mirror, can be used to fine-tune the cavity length to achieve laser tuning. The preferred stroke of this piezoelectric ceramic is 3.3 μm, the maximum voltage is 200 V, and the accuracy of the corresponding voltage control circuit is preferably 0.002 V. When the cavity length is preferably 10 mm, the tuning accuracy of the piezoelectric ceramic is 1.16 MHz, and the tunable range is the smaller of the free spectral range and the transmission bandwidth of the atomic filter.

[0046] Furthermore, the miniature Faraday laser also includes a laser housing and a base, with all components mounted on the base. The reflecting cavity mirror 4 and the piezoelectric ceramic 5 can be fixed at different positions on the base, so the cavity length of the laser can be adjusted between 10 mm and 80 mm.

[0047] The values ​​of the above-mentioned devices are all preferred values. The embodiments of the present invention are only used as examples for illustration. In specific implementation, the embodiments of the present invention do not limit these values.

[0048] This invention significantly increases the transmission bandwidth of the atomic filter by increasing the buffer gas pressure in the alkali metal atom gas cell, enabling it to cover the hyperfine energy level transition lines of the alkali metal atom ground state. This reduces the difficulty of subsequent frequency locking. The increased transmission bandwidth also further enhances the Faraday laser's resistance to interference from changes in laser operating current and temperature. By compressing the cavity length of the Faraday laser to a limit of 1 cm, single-frequency output is achieved while simultaneously increasing the laser's free spectral range to 14.65 GHz, greatly expanding the laser's sweep range and broadening its application scope. This miniature Faraday laser solves the problems of subsequent frequency locking difficulties, small sweep range, and large size of mainstream large-cavity Faraday lasers, significantly improving the output laser performance and portability of Faraday lasers and broadening their applications in semiconductor laser-related fields such as optical communication, optical computing, and lidar.

[0049] Example 2

[0050] The following is combined with Figure 2 and Figure 3 The solution in Example 1 will be further described below:

[0051] Figure 1 This is a schematic diagram of a miniature Faraday laser designed for an embodiment of the present invention. The laser consists of: a laser diode 1, a collimating lens 2, a miniature Faraday atom filter 3, a reflecting cavity mirror 4, and a piezoelectric ceramic 5.

[0052] In this embodiment of the invention, a laser diode 1 with a typical wavelength of 860nm and a gain range of 830–880nm is used as an example. In specific implementations, other types of laser diodes can be selected, such as laser diodes with a typical wavelength of 780nm. This embodiment of the invention does not impose any limitations on this. A semiconductor cooler with a rated voltage of 12V and a cooling power of 76.3W is placed immediately below the laser diode. The cold side of the cooler contacts the copper base that holds the laser diode, and the hot side contacts the laser base. The copper base serves two purposes: securing the laser diode and increasing the contact area between the laser diode and the semiconductor cooler, thereby increasing heat dissipation. The semiconductor cooler and a thermistor placed inside the copper base are connected to an external temperature control circuit to detect and control the temperature.

[0053] In this embodiment of the invention, the alkali metal atom gas chamber in the micro Faraday atom filter 3 is illustrated using a cesium atom gas chamber filled with 50 Torr argon gas as an example. Other types of atom gas chambers can be selected in specific implementations, and this embodiment of the invention does not impose any limitations on this. The cesium atom gas chamber has a diameter of 7 mm and a length of 3, 5, 8, or 10 mm. This embodiment of the invention uses a 3 mm long cesium atom gas chamber made of quartz. Anti-reflection films are coated at both ends of the gas chamber, achieving a laser transmittance of 96% at a wavelength of 852 nm. The cesium atom gas chamber, magnetic field generating device, temperature control module, and two polarizers are assembled together by a special outer shell with a thickness of 5 mm in the laser propagation direction (3 mm for the gas chamber length plus 2 mm for the outer shell thickness). Considering the distance of 4.57mm between the collimating lens 2 and the laser diode 1, the minimum cavity length of the miniature Faraday laser is 9.57mm. The cavity length can be increased by increasing the distance between the reflecting cavity mirror 4 and the end face of the laser diode 1. This embodiment of the invention takes a cavity length of 10mm as an example for explanation. Other cavity lengths can also be selected for specific implementation.

[0054] Furthermore, the transmission spectrum of the miniature Faraday atom filter 3, which uses a 3mm long cesium atom gas cell filled with 50 Torr argon gas, is as follows: Figure 2As shown, its transmission bandwidth is 14.65 GHz, and its maximum transmittance is 24.65%. For a miniature Faraday laser with a cavity length of 10 mm, its free spectral range is 15 GHz, i.e., the longitudinal mode spacing is 15 GHz. Figure 2 The two straight lines represent two adjacent longitudinal modes of the laser. Therefore, when the laser is tuned using the piezoelectric ceramic 5, only one longitudinal mode exists within the transmission bandwidth of the atomic filter 3, resulting in single-frequency laser output. For a Faraday laser with a cavity length of 300 mm and a longitudinal mode spacing of 0.5 GHz, its longitudinal mode distribution is as follows... Figure 3 As shown, there are 29 longitudinal modes within the bandwidth of atomic filter 3, making it easy for the laser to produce dual-frequency or even multi-frequency laser output.

[0055] The reflector mirror 4 is attached to the piezoelectric ceramic 5. The thickness of the piezoelectric ceramic 5 is changed by altering the voltage applied to it, thereby changing the laser cavity length for laser tuning. The piezoelectric ceramic 5 has a maximum voltage of 200V and a maximum stroke of 3.3μm, which is greater than half the laser output wavelength, thus allowing for a tunable range with a longitudinal mode spacing of 15GHz. The voltage source for the piezoelectric ceramic 5 has a maximum voltage of 150V, divided into 65534 steps, each step being 2.28mV, corresponding to a frequency change of 1.16MHz. The reflector mirror 4 and the piezoelectric ceramic 5 are attached together to a mirror mount. The mount can be either a screw-type mount for pitch adjustment or a screwless mount for pitch adjustment. The screwless mount uses a steel shim to change the pitch of the reflector mirror. Generally, a screw-type mount is more convenient for adjustment, while a screwless mount offers better mechanical stability; therefore, a screwless mount is preferred.

[0056] Example 3

[0057] Figure 3 The above-mentioned method for realizing and tuning a miniature Faraday laser includes the following steps:

[0058] Step 101: Assemble the laser diode 1, the thermistor, and the semiconductor cooler onto the copper base. Assemble the temperature control module, the magnetic field generator, the cesium atom gas chamber filled with 50 Torr of argon gas, and the two polarizers into an atomic filter 3. Set the polarization directions of the two polarizers to be parallel. Attach the reflective cavity mirror 4 and the piezoelectric ceramic 5 to the mirror base. Finally, install the copper base containing the laser diode 1, the atomic filter 3, and the mirror base containing the reflective cavity mirror 4 onto the laser's base.

[0059] Step 102: By changing the pitch of the mirror mount by using a steel shim, the feedback of the laser is adjusted so that the cavity feedback of the laser reaches its maximum. The laser returns along the original path at the end face of the reflecting cavity mirror 4, and the laser output power reaches its maximum, with a wavelength of 830-880nm.

[0060] Step 103: Rotate the polarizer near the reflecting cavity mirror 4 in the atomic filter 3 so that the polarization directions of the two polarizers are orthogonal. At this time, the laser cannot pass through the atomic filter 3, the laser is turned off, and the output power of the laser is 0. Then, increase the temperature of the atomic gas chamber. Under the action of Faraday rotation, the polarization direction of the laser rotates in the atomic gas chamber. At a suitable temperature, the transmittance of the atomic filter 3 reaches its maximum, the laser is turned back on, the laser output power is at its maximum, and the laser wavelength is within the 14.65 GHz bandwidth of the atomic filter 3.

[0061] Step 104: Adjust the voltage of the piezoelectric ceramic 5 to change the laser cavity length and achieve tuning of the output laser. The wavelength of the laser varies within the transmission bandwidth of the atomic filter 3, which is 14.65 GHz.

[0062] In this embodiment of the invention, by using a thin-film polarizer to replace the large-volume polarizing beam splitter and Glan Taylor prism, using a self-designed atomic filter housing (i.e., including a laser base, four side plates, and a cover plate for fixing the components in the laser and assembling them into a whole) to fix the components while compressing the thickness along the laser transmission direction, and by making the collimating lens 2 and the reflecting cavity mirror 4 as close to the atomic filter as possible, the cavity length of the laser can be reduced to a minimum of 9.57 mm, thus improving the free spectral range of the Faraday atomic filter 3 by two orders of magnitude compared to the mainstream. Furthermore, by filling the atomic gas chamber with a high-pressure buffer gas, this embodiment of the invention increases the transmission bandwidth of the atomic filter 3 to 14.65 GHz, which is close to the 15 GHz free spectral range of the Faraday laser. On the one hand, by adjusting the piezoelectric ceramic 5, it is easy to make a single laser longitudinal mode exist within the transmission spectrum bandwidth at only one time, thus achieving stable single-frequency laser output. On the other hand, by adjusting the piezoelectric ceramic 5, the emitted laser can be tuned over a wide range, with a tunable range of 14.65 GHz, which is two orders of magnitude higher than the tunable range of mainstream Faraday lasers.

[0063] The above embodiments are only for illustrating the principle of the present invention. The parameters of the laser diode 1 in the miniature Faraday laser, the gas chamber size, buffer gas pressure, magnetic field strength, etc. in the atomic filter 3, the transmittance-to-reflection ratio of the reflecting cavity mirror 4, and the stroke of the piezoelectric ceramic can all be replaced, and are not limited to the embodiments of the present invention.

[0064] Unless otherwise specified, the model numbers of the various devices in this embodiment of the invention are not limited, and any device that can perform the above functions is acceptable.

[0065] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A miniature single-frequency Faraday laser with an ultra-large tunable range, characterized in that, The laser includes: A laser diode coated with an antireflection coating is used as a seed source for a Faraday laser. The collimation module, comprising a collimating lens and a corresponding fixing structure, is used to collimate the laser diode; A miniature Faraday atom filter filters the laser light emitted from a laser diode, and the final output laser light is determined by the transmission spectrum of the filter. Filling the atomic gas chamber with a high-pressure buffer gas increases the tunable range of the Faraday laser from 250 MHz to 15 GHz. A reflective cavity mirror with a preset reflectivity reflects the filtered laser light back into the resonant cavity, forming oscillations and generating stable laser light. The remaining laser light is transmitted out of the laser device through the reflective cavity mirror. The temperature control module, consisting of a TEC semiconductor cooler and a temperature feedback circuit, is used to regulate the operating temperature of the laser diode. The integrated mechanical structure of the laser includes: a base, four side plates and a cover plate, which are used to fix the components in the laser and assemble the components into a whole. The micro Faraday atom filter includes: Alkali metal atom gas chamber, filled with alkali metal atoms and buffer gas for transmission spectrum broadening and shaping; The magnetic field generating device is a ring-shaped permanent magnet; Another temperature control module monitors and provides feedback control of the temperature of the alkali metal atom gas chamber; The polarization filter module consists of two polarization splitters with orthogonal polarization directions, located on both sides of the alkali metal atom gas cell, to filter laser light whose polarization direction rotates under the action of a magnetic field; With a transmission bandwidth of 14.64 GHz, the cavity length of the Faraday laser is compressed to the limit of 1 cm, achieving single-frequency output while increasing the free spectral range of the laser to 14.65 GHz.

2. The miniature single-frequency Faraday laser with an ultra-large tunable range according to claim 1, characterized in that, The back of the reflective cavity mirror is attached with piezoelectric ceramic, which changes the laser cavity length when the laser is working, thereby adjusting the frequency of the output laser.

3. A miniature single-frequency Faraday laser with an ultra-large tunable range according to claim 1, characterized in that, The reflective cavity mirror is mounted on a mirror mount, and the cavity length of the laser is adjusted by changing the position of the mirror mount.

4. A method for single-frequency output of a miniature single-frequency Faraday laser with an ultra-large tunable range, characterized in that, The method is used in the miniature single-frequency Faraday laser with an ultra-large tunable range as described in any one of claims 1-3, and the method includes: A laser diode with a temperature control module and a collimation module is mounted on a laser base. The position of the lens in the collimation module is adjusted to minimize the divergence angle of the laser emitted from the collimation module. A miniature Faraday atom filter equipped with a temperature control module and a magnetic field generator is mounted on the laser base. The polarization directions of the two polarizers are set to be parallel, and the temperature control module is turned off. The mirror mount containing the reflective cavity mirror and piezoelectric ceramic is assembled onto the laser base. By adjusting the pitch of the mirror mount, the pitch of the reflective cavity mirror is changed, so that the laser reflected at the cavity mirror returns along the original path, so that the feedback of the resonant cavity reaches the maximum and the laser starts to oscillate. By rotating the polarizer near the reflecting cavity mirror, making its polarization direction orthogonal to that of another polarizer, the laser cannot oscillate. When the temperature control module of the atomic filter is turned on, the polarization direction of the laser near the atomic transition frequency rotates by 90° under the Faraday rotation effect, causing the laser near this frequency to be emitted from the orthogonal polarizer. The resonant cavity loss decreases, the laser restarts, and the frequency of the output laser is near the atomic transition frequency. Changing the voltage of the piezoelectric ceramic changes its thickness, which in turn changes the cavity length of the laser, thus altering the laser's output frequency.

5. The single-frequency output method of a miniature single-frequency Faraday laser with an ultra-large tunable range according to claim 4, characterized in that, The tunable range of a laser is determined by the smaller of the laser's free spectral range and the transmission bandwidth of the atomic filter. When the operating frequency exceeds the transmission bandwidth of the atomic filter, the laser cavity loss is too large and the laser is turned off. The tunable range is the transmission bandwidth of the atomic filter. When the operating frequency exceeds one boundary of the free spectral range, the operating frequency will jump to the other boundary of the free spectral range.

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