A dual-cavity coupling integrated structure frequency stabilizer based on a fabry-perot cavity and a preparation method thereof

Abstract

The application provides a dual-cavity coupling integrated structure frequency stabilizer based on a Fabry-Perot cavity and a preparation method, and belongs to the technical field of laser frequency stabilization. The dual-cavity coupling integrated structure frequency stabilizer comprises a Fabry-Perot cavity module and an atomic gas chamber cavity module, and the Fabry-Perot cavity module is located above the atomic gas chamber cavity module. The Fabry-Perot cavity module comprises a first plane glass, a second plane glass, a cylindrical glass cylinder, a ring-shaped piezoelectric ceramic sheet, a plane cavity mirror, a vacuum chamber and a concave cavity mirror. The atomic gas chamber cavity module comprises a cylindrical silicon gas chamber wall, the second plane glass, a piece of plane borosilicate glass and an atomic gas chamber cavity. The second plane glass is shared by the Fabry-Perot cavity module and the atomic gas chamber cavity module. A predetermined alkali compound material is arranged in the atomic gas chamber cavity and corresponds to a laser central wavelength. By integrating the functions of the Fabry-Perot cavity module and the atomic gas chamber cavity module, the number of components is reduced, and the cost is lowered.

Description

Technical Field

[0001] This invention belongs to the field of laser frequency stabilization technology, and particularly relates to a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity and its fabrication method. Background Technology

[0002] In modern optics and quantum physics research, the generation and application of narrow-linewidth lasers is an important research direction. Narrow-linewidth lasers possess high coherence and high frequency stability, and are widely used in high-resolution spectral analysis, atomic clocks, quantum information processing, precision measurement, and nonlinear optics. However, traditional lasers typically have large output linewidths, making it difficult to meet the demands of high-precision experiments and applications. Meanwhile, with the development of integrated photonics, miniaturized and integrated optical path systems have become the mainstream. Therefore, how to effectively narrow the laser linewidth to obtain laser sources with high integration, high coherence, and high stability has become one of the core research topics in optical technology. The Fabry-Perot (FP) cavity, as a high-precision optical device, uses two high-reflectivity mirrors to form a resonant cavity, performing multiple reflections and interferences of light to achieve highly selective transmission of specific wavelengths. The Fabry-Perot cavity has extremely high frequency resolution; its free spectral range and spectral fineness can be adjusted by the cavity length and mirror reflectivity, thereby effectively narrowing the input laser linewidth. The laser output light is injected into a Fabry-Perot cavity, and the resonant characteristics of the Fabry-Perot cavity are used to select a laser beam of a specific frequency, resulting in an output laser with extremely narrow linewidth and higher coherence. On the other hand, the atomic gas chamber, as an important device for studying the interaction between atoms and light, can provide an absolute frequency reference for laser frequency locking. The gaseous atoms (such as rubidium, cesium, or other alkali metal atoms) filling the chamber have specific energy level transition characteristics, and their absorption or emission spectral lines can serve as a reference for laser frequency locking. By inputting a narrow-linewidth laser into the atomic gas chamber and detecting the atomic absorption or emission signals, precise laser frequency locking can be further achieved, thereby obtaining a laser output with extremely high frequency stability.

[0003] Chinese patent publication CN113178774A discloses a method for locking a semiconductor laser frequency to a high-precision Fabry-Royce cavity. This method employs optical feedback, using a combination of a half-wave plate, a polarizing beam-splitting prism, and a quarter-wave plate. By adjusting the feedback coefficient, a wide range of adjustments can be made without sacrificing the intensity of the incident light. The feedback phase is controlled by adjusting the stretching of a piezoelectric ceramic bonded to a reflector, thus avoiding optical feedback caused by direct reflection. This method can achieve stable locking of a semiconductor laser to a high-precision Fabry-Royce optical cavity and can be applied to laser linewidth reduction and high-sensitivity cavity-enhanced spectroscopy. Compared to traditional optical feedback cavity locking systems, the use of a linear optical cavity instead of a V-shaped cavity allows for the construction of a more precise optical cavity, thereby achieving more sensitive laser spectroscopy.

[0004] Chinese Patent Publication CN114442009A discloses a frequency stabilization method and system for an atomic magnetometer based on FP cavity frequency stabilization, comprising: adjusting the frequency of a pump laser to minimize the intensity of a first pump laser passing through the atomic gas chamber cavity; adjusting the frequency of a detection laser to minimize the intensity of a first detection laser passing through the atomic gas chamber cavity; a frequency reference laser, a second pump laser, and a second detection laser jointly entering the FP cavity; applying a set sweep voltage to the FP cavity; detecting the resonant transmission signals of the frequency reference laser, the second pump laser, and the second detection laser; stabilizing the frequency of the pump laser based on the transmission peak position difference between the second pump laser and the frequency reference laser; and stabilizing the frequency of the detection laser based on the transmission peak position difference between the second detection laser and the frequency reference laser.

[0005] Existing Fabry-Perot cavities are mostly used for frequency stabilization of reflected light (Pound-Drever-Hall, PDH) or Fabry-Perot interferometers, and are large, heavy, and costly. Frequency stabilization techniques using atomic gas chambers for saturated absorption or atomic transitions face the problem of large size, making miniaturization and integration impossible. Furthermore, Fabry-Perot cavities and atomic gas chambers require separate tuning and control during operation, increasing the system's operational complexity. Therefore, existing frequency stabilization technologies cannot meet the technical requirements for miniaturized laser frequency stabilization. An integrated, ultra-stable frequency stabilizer is needed as an optical frequency standard locking device, especially one using micro / nano fabrication technology to achieve a miniature, ultra-stable frequency stabilizer fabricated in a single integrated unit. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the first aspect of the present invention proposes a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity, wherein the dual-cavity coupled integrated structure frequency stabilizer includes: a Fabry-Perot cavity module and an atomic gas chamber module, wherein the Fabry-Perot cavity module is located above the atomic gas chamber module; The Fabry-Perot cavity module includes: a first planar glass, a second planar glass, a cylindrical glass tube, an annular piezoelectric ceramic sheet, a planar cavity mirror, a vacuum chamber, and a concave cavity mirror; The first planar glass is sealed to the upper end of the cylindrical glass tube, and the second planar glass is sealed to the lower end of the cylindrical glass tube. A cavity is formed by the inner surfaces of the first and second planar glass and the inner surface of the cylindrical glass tube. Within this cavity, from bottom to top, are the concave cavity mirror, the vacuum chamber, the planar cavity mirror, and the annular piezoelectric ceramic sheet. The upper side of the annular piezoelectric ceramic sheet is sealed to the inner surface of the first planar glass. The lower side of the annular piezoelectric ceramic sheet is sealed to the upper side of the planar cavity mirror. The vacuum chamber is formed by the lower side of the planar cavity mirror, the inner surface of the cylindrical glass tube, and one concave side of the concave cavity mirror. The concave surface of the concave cavity mirror faces the vacuum chamber, and the planar side of the concave cavity mirror is sealed to the inner surface of the second planar glass. The atomic gas chamber module includes: a cylindrical silicon gas chamber wall, a second planar glass, a planar borosilicate glass, and an atomic gas chamber; the second planar glass is shared by the Fabry-Perot cavity module and the atomic gas chamber module; The upper end of the cylindrical silicon gas chamber wall is sealed to the outer surface of the second planar glass, and the lower end of the cylindrical silicon gas chamber wall is sealed to the inner surface of a planar borosilicate glass. An atomic gas chamber is formed by the inner surface of the cylindrical silicon gas chamber wall, the outer surface of the second planar glass, and the inner surface of the planar borosilicate glass. A predetermined alkali metal compound material is placed in the atomic gas chamber. The laser wavelength absorbed or emitted by the predetermined alkali metal compound material corresponds to the laser center wavelength stabilized by the Fabry-Perot cavity module.

[0007] As described in the first aspect of the present invention, the integrated structure frequency stabilizer comprises a first planar glass plate coated with an antireflection film targeting the center wavelength of the incident laser beam in the direction facing the incident laser beam; and a second planar glass plate coated with an antireflection film targeting the center wavelength of the incident laser beam on the side facing the atomic gas chamber cavity; the transmittance of the antireflection film is ≥90%, and the first planar glass, the cylindrical glass tube, and the second planar glass are all made of ultra-low expansion coefficient glass, wherein the expansion coefficient of the ultra-low expansion coefficient glass at room temperature is less than 1×10⁻⁶. -8 K -1 .

[0008] As described in the first aspect of the present invention, in the integrated structure frequency stabilizer, the Fabry-Perot cavity module has a semi-permeable film coated on the surface of both the planar cavity mirror and the concave cavity mirror, which is directed to the center wavelength of the incident laser beam. The surfaces of the semi-permeable film are arranged in the opposite direction of the planar cavity mirror and the concave cavity mirror. The reflectivity of the semi-permeable film at the center wavelength of the laser is 30-70%, and the loss rate is <10 ppm. The semi-permeable film is a high-reflectivity film for light wavelengths other than the center wavelength of the laser, and the reflectivity of the high-reflectivity film is ≥99.99%, and the loss rate is <10 ppm. The semi-permeable film and the high-reflectivity film are composed of alternating stacks of silicon oxide and tantalum pentoxide.

[0009] As described in the first aspect of the present invention, the sealing connection methods for the various parts of the Fabry-Perot cavity module and the atomic gas chamber module include: bonding, welding and bonding.

[0010] As described in the first aspect of the present invention, in the integrated structure frequency stabilizer, the electrode leads of the annular piezoelectric ceramic sheet are led out from inside the Fabry-Perot cavity module through a first planar glass.

[0011] As described in the first aspect of the present invention, in the integrated structure frequency stabilizer, the alkali metal of the predetermined alkali metal compound material in the atomic gas chamber is one of rubidium, potassium, or cesium.

[0012] A second aspect of the present invention provides a method for fabricating a frequency stabilizer based on a Fabry-Perot cavity dual-cavity coupled integrated structure as described in any of the preceding claims, comprising: Step 1: Fabricate a planar cavity mirror on the first planar glass; including: An antireflective coating targeting the center wavelength of the incident laser beam is deposited on the outer surface of the first planar glass. An annular piezoelectric ceramic sheet is bonded to the inner surface of the first planar glass. A planar cavity mirror is bonded to the other side of the annular piezoelectric ceramic sheet. Multiple layers of silicon oxide film and tantalum pentoxide film are alternately deposited on the cavity mirror surface of the planar cavity mirror to form a semi-permeable film targeting the incident laser beam. Step 2: Fabricate a concave cavity mirror on the second planar glass; Step 3: The first planar glass, the cylindrical glass tube, the second planar glass, the annular piezoelectric ceramic sheet, the planar cavity mirror, and the concave cavity mirror are connected in a sealed manner to form a Fabry-Perot cavity module; Step 4: Fabricate the cylindrical silicon gas chamber wall; Step 5: The second planar glass, the cylindrical silicon gas chamber wall, and a piece of planar borosilicate glass are connected in a sealed manner to form an atomic gas chamber; and a predetermined alkali metal compound material is placed inside the atomic gas chamber. Step 6: Use ultraviolet light to irradiate the atomic gas chamber to generate gaseous alkali metal atoms, and fabricate a micro dual-cavity coupled integrated structure frequency stabilizer.

[0013] As described in the second aspect of the present invention, step 2 includes the following sub-steps; Step 2.1: Deposit an antireflective coating on one plane of the second planar glass to the center wavelength of the incident laser beam; Step 2.2: Photolithographically etch the outer contour of the concave cavity mirror onto another plane of the second planar glass; Step 2.3: Photolithographically create the target pattern of the concave mirror on the outer contour surface of the concave cavity mirror; Step 2.4: Use a hot air gun to blow the center of the concave mirror target pattern to melt the glass and make a smooth concave cavity mirror surface. While the glass is melting, adjust the mirror cavity radius of the concave mirror by adjusting the air speed of the hot air gun. Step 2.5: Alternately deposit silicon oxide film and tantalum pentoxide film on the concave cavity mirror to form a semi-permeable film that is sensitive to the center wavelength of the incident laser beam. Step 2.6 The concave cavity mirror is polished by single-sided polishing and chemical mechanical polishing techniques in sequence to obtain a concave cavity mirror with high reflectivity, wherein the high reflectivity is: reflectivity ≥ 99.99%.

[0014] As described in the second aspect of the present invention, step 4, fabricating the cylindrical silicon gas chamber wall, includes the following sub-steps: Step 4.1: Spin-coat a layer of photoresist onto the silicon wafer and use photolithography to obtain a gas cell pattern; Step 4.2: Ion etching is used on the silicon wafer until the silicon wafer is penetrated to form a cylindrical silicon gas chamber wall.

[0015] As described in the second aspect of the present invention, step 5 includes: selecting a predetermined alkali metal compound material and placing it into the atomic gas chamber cavity according to the laser center wavelength of the incident laser beam.

[0016] The method of the present invention has the following advantages: This invention discloses a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity. By introducing a ring-shaped piezoelectric ceramic sheet into the Fabry-Perot cavity, the cavity length is adjusted through reflected light feedback, thereby adjusting the resonant frequency of the Fabry-Perot cavity.

[0017] This invention discloses a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity. The Fabry-Perot cavity and the atomic gas chamber are functionally integrated, reducing additional optical components and control systems, and lowering overall manufacturing costs. The dual-cavity coupled integrated structure frequency stabilizer based on the Fabry-Perot cavity can extend its operating wavelength range to the D1 / D2 line saturation absorption of rubidium atoms (795 / 780 nm), the D1 / D2 line saturation absorption of cesium atoms (894 / 852 nm), and the D1 / D2 line saturation absorption of potassium atoms (770 / 776 nm). Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity according to the present invention; Figure 2a-2k This is a schematic diagram of steps S1-S11 of the fabrication method of a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity according to the present invention. Figure 3l-3r This is a schematic diagram of steps S12-S18 of the fabrication method of a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity according to the present invention. Figure 4s-4v This is a schematic diagram of steps S19-S22 of the fabrication method of a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity according to the present invention. Figure 5 This is a schematic diagram illustrating a two-photon transition frequency stabilization implementation method for a dual-cavity coupled integrated structure frequency stabilizer based on a Brie-Perot cavity according to the present invention.

[0019] Among them, 1. Ring-shaped piezoelectric ceramic sheet; 2. Planar cavity mirror; 3. Vacuum chamber; 4. Cylindrical glass tube; 5-1. First planar glass; 5-2. Second planar glass; 6. Concave cavity mirror; 7. Cylindrical silicon gas chamber wall; 8. Atomic gas chamber cavity; 9. Planar borosilicate glass; 10. Electrode leads.

[0020] 2-1 Semiconductor laser; 2-2 Optical isolator; 2-3 Phase modulator; 2-4 Photodetector; 2-5 Optical beam splitter; 2-6 Fabry-Perot cavity dual-cavity coupled integrated structure frequency stabilizer; 2-7 10 nm filter; 2-8 Photomultiplier tube; 2-9 First frequency locking module; 2-10 Second frequency locking module. Detailed Implementation

[0021] This invention relates to a Fabry-Perot cavity-based dual-cavity coupled integrated structure frequency stabilizer and its fabrication method. The Fabry-Perot cavity-based dual-cavity coupled integrated structure frequency stabilizer is used for laser frequency stabilization. This dual-cavity coupled integrated structure frequency stabilizer is small in size and lightweight, and is fabricated using micro-nano technology. It can be applied to on-chip atomic optical clocks, on-chip optical frequency standards, integrated photonics, and other products.

[0022] This invention utilizes the characteristic of Fabry-Perot cavities to significantly narrow the linewidth of the wide-linewidth laser beam output by a laser, and provides an absolute frequency reference through an atomic gas chamber 8. Using micro-nano fabrication technology, an optical frequency standard locking frequency stabilizer with a micro dual-cavity coupled integrated structure is achieved through integrated fabrication.

[0023] This dual-cavity coupled integrated frequency stabilizer based on a Fabry-Perot cavity combines a Fabry-Perot cavity with an atomic gas chamber, significantly reducing size and weight and meeting the demands of miniaturized frequency stabilizer applications. The integrated physical structure design reduces optical path drift and environmental noise, improving the system's environmental robustness.

[0024] This invention discloses a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity. By introducing a ring-shaped piezoelectric ceramic sheet 1 within the Fabry-Perot cavity, the cavity length is adjusted via reflected light feedback, thereby regulating the resonant frequency of the Fabry-Perot cavity. Simultaneously, the Fabry-Perot cavity and the atomic gas chamber 8 are functionally integrated into one unit, reducing additional optical components and control systems, and lowering the overall manufacturing cost.

[0025] The present invention discloses a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity, the operating wavelength range of which can be extended to the saturated absorption of rubidium atoms D1 / D2 lines (795 / 780 nm), cesium atoms D1 / D2 lines (894 / 852 nm), and potassium atoms D1 / D2 lines (770 / 776 nm).

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention. Other embodiments obtained based on the embodiments of the present invention without creative effort are also within the protection scope of the present invention.

[0027] One embodiment of the present invention provides a frequency stabilizer based on a Fabry-Perot cavity dual-cavity coupled integrated structure, the specific structure of which is shown in the attached figure. Figure 1 As shown.

[0028] A dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity, the dual-cavity coupled integrated structure frequency stabilizer comprising: a Fabry-Perot cavity module and an atomic gas chamber module; The Fabry-Perot cavity module includes: a first planar glass 5-1, a second planar glass 5-2, a cylindrical glass tube 4, an annular piezoelectric ceramic sheet 1, a planar cavity mirror 2, a vacuum chamber 3, and a concave cavity mirror 6; The first planar glass 5-1 is sealed to the upper end of the cylindrical glass tube 4, and the second planar glass 5-2 is sealed to the lower end of the cylindrical glass tube 4. The inner side of the first planar glass 5-1, the upper side of the second planar glass 5-2, and the inner side of the cylindrical glass tube 4 together form a cavity. From bottom to top, the cavity contains the concave cavity mirror 6, the vacuum chamber 3, the planar cavity mirror 2, and the annular piezoelectric ceramic sheet 1. The upper side of the annular piezoelectric ceramic sheet 1 is sealed to the inner side of the first planar glass 5-1. The lower side of the annular piezoelectric ceramic sheet 1 is sealed to the upper side of the planar cavity mirror 2. The lower side of the planar cavity mirror 2, the inner side of the cylindrical glass tube 4, and the concave surface of the concave cavity mirror 6 together form the vacuum chamber 3. The concave surface of the concave cavity mirror 6 faces the vacuum chamber 3, and the planar side of the concave cavity mirror 6 is sealed to the upper side of the second planar glass 5-2. The atomic gas chamber module includes: a cylindrical silicon gas chamber wall 7, a second planar glass 5-2, a planar borosilicate glass 9, and an atomic gas chamber 8; The second planar glass 5-2 is shared by the Fabry-Perot cavity module and the atomic gas chamber module; The upper end of the cylindrical silicon gas chamber wall 7 is sealed to the lower side of the second planar glass 5-2, and the lower end of the cylindrical silicon gas chamber wall 7 is sealed to the inner side of a planar borosilicate glass 9. The inner side of the cylindrical silicon gas chamber wall 7, the lower side of the second planar glass 5-2, and the inner side of the planar borosilicate glass 9 form an atomic gas chamber cavity 8, in which a predetermined alkali metal compound material is placed. The laser wavelength absorbed or emitted by the predetermined alkali metal compound material corresponds to the laser center wavelength stabilized by the Fabry-Perot cavity module.

[0029] The first planar glass 5-1, the second planar glass 5-2, and the cylindrical glass tube 4 mentioned above are all made of ultra-low expansion coefficient glass, which has an expansion coefficient of less than 1×10⁻⁶ at room temperature. -8 K -1 .

[0030] See attached document Figure 5This diagram illustrates the two-photon transition frequency stabilization mechanism of a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity. The incident laser generated by semiconductor laser 2-1 enters the Fabry-Perot cavity through the first planar glass 5-1. The incident laser undergoes multiple reflections between the planar cavity mirror 2 and the concave cavity mirror 6, forming multiple beams. These beams superimpose and interfere. When the optical path length satisfies the cavity's resonance condition, the light wave passes through the Fabry-Perot cavity; other light waves that do not meet the resonance condition are reflected. The transmitted light enters the atomic gas chamber 8 through the second planar glass 5-2. In the atomic gas chamber 8, the transmitted light is absorbed by atoms, causing transitions. A photodetector / photomultiplier tube detects the transition signal and mixes it using an externally modulated reference frequency. An error signal is then fed back to the laser to stabilize its frequency. The light waves reflected in the Fabry-Perot cavity are detected by a photodetector and mixed by an externally modulated reference frequency to form an error signal that is fed back to the controller (not shown). The controller outputs a control voltage to the annular piezoelectric ceramic plate 1 in the Fabry-Perot cavity. This control voltage adjusts the elongation or shortening deformation of the annular piezoelectric ceramic plate 1 to adjust the cavity length of the Fabry-Perot cavity, thereby controlling the resonant frequency / center wavelength of the Fabry-Perot cavity.

[0031] As described in the integrated structure frequency stabilizer of this invention, the first planar glass 5-1 facing the incident laser beam is coated with an anti-reflection film against the center wavelength of the incident laser beam; the second planar glass 5-2 facing the atomic gas chamber 8 is coated with an anti-reflection film against the center wavelength of the incident laser beam; the transmittance of the anti-reflection film is ≥90%, and the first planar glass 5-1, the cylindrical glass tube 4, and the second planar glass 5-2 are all made of ultra-low expansion coefficient glass, which has an expansion coefficient of less than 1×10 at room temperature. -8 K -1 .

[0032] In the integrated structure frequency stabilizer described in this invention, the Fabry-Perot cavity module has a semi-transparent film coated on the surface of both the planar cavity mirror 2 and the concave cavity mirror 6, which is oriented towards the center wavelength of the incident laser beam. The surfaces of the semi-transparent film are arranged in the opposite direction of the planar cavity mirror 2 and the concave cavity mirror 6. The reflectivity of the semi-transparent film at the center wavelength of the laser is 30-70%, and the loss rate is <10 ppm. The semi-transparent film is a high-reflectivity film for wavelengths other than the center wavelength of the laser, and the reflectivity of the high-reflectivity film is ≥99.99%, and the loss rate is <10 ppm. The semi-transparent film and the high-reflectivity film are composed of alternating stacks of silicon oxide and tantalum pentoxide.

[0033] As described in this invention, the sealing connection methods for the various parts of the Fabry-Perot cavity module and the atomic gas chamber module include: bonding, welding, and bonding.

[0034] As described in the integrated structure frequency stabilizer of the present invention, the electrode lead 10 of the annular piezoelectric ceramic sheet 1 passes through the first planar glass 5-1 and is led out from inside the Fabry-Perot cavity module.

[0035] As described in the first aspect of the present invention, in the integrated structure frequency stabilizer, the alkali metal of the predetermined alkali metal compound material of the atomic gas chamber 8 is one of rubidium, potassium or cesium.

[0036] A second aspect of the present invention provides a method for fabricating a frequency stabilizer based on a Fabry-Perot cavity dual-cavity coupled integrated structure as described in any of the preceding claims, comprising: Step 1: Fabricate a planar cavity mirror 2 on the first planar glass 5-1; including: An antireflective coating for the center wavelength of the incident laser beam is deposited on one plane of the first planar glass 5-1. One side of the annular piezoelectric ceramic sheet 1 is bonded to the other plane of the first planar glass 5-1. A planar cavity mirror 2 is bonded to the other side of the annular piezoelectric ceramic sheet 1. Multilayer silicon oxide film and tantalum pentoxide film are alternately deposited on the mirror surface of the planar cavity mirror 2 to form a semi-permeable film for the incident laser beam. Step 2: Fabricate a concave cavity mirror 6 on the second planar glass 5-2; Step 3: Use a sealing connection method to form a Fabry-Perot cavity by connecting the first flat glass 5-1, the cylindrical glass tube 4, and the second flat glass 5-2. Step 4: Fabricate the cylindrical silicon gas chamber wall 7; Step 5: The second planar glass 5-2, the cylindrical silicon gas chamber wall 7, and a piece of planar borosilicate glass 9 are connected in a sealed manner to form an atomic gas chamber 8; and a predetermined alkali metal compound material is placed in the atomic gas chamber 8. Step 6: Use ultraviolet light to irradiate the atomic gas chamber 8 to generate gaseous alkali metal atoms, and fabricate a micro dual-cavity coupled integrated structure frequency stabilizer.

[0037] The method for fabricating a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity proposed in this invention is shown in Figures 2-4. The fabrication of the Fabry-Perot cavity includes the following steps: S1. As shown in Figure 2a, prepare a second planar glass 5-2 with an anti-reflection coating on one side of the incident laser wavelength. S2. As shown in Figure 2b, a layer of photoresist is spin-coated on the second planar glass 5-2. The photomask is a concave cavity mirror 6 pattern. After the concave cavity mirror 6 pattern is photolithographically formed, a layer of aluminum is deposited on the concave cavity mirror 6 pattern as an etching stop layer using physical vapor deposition. S3. As shown in Figure 2c, the deposited second planar glass 5-2 is stripped of adhesive and aluminum in a stripping solution; only the aluminum etching stop layer is preserved. S4. As shown in Figure 2d, the second planar glass 5-2 is etched using deep reactive ion etching to form the outer contour of the concave cavity mirror 6. S5. As shown in Figure 2e, after forming the outer contour of the concave cavity mirror 6, the aluminum etching stop layer is removed by wet method. S6. As shown in Figure 2f, a layer of photoresist is spin-coated on the outer contour of the concave cavity mirror 6. The mask is a target pattern smaller than the outer contour of the concave cavity mirror 6. After photolithography of the target pattern, an aluminum etch stop layer is deposited on the outside of the target pattern by physical vapor deposition. The photoresist and aluminum are removed in the photoresist remover solution. Only the aluminum etch stop layer on the outside of the target pattern is preserved. S7. As shown in g in Figure 2, the target pattern area of ​​the second planar glass 5-2 is etched by deep reactive ion etching, forming a concave "U" shape with the periphery of the concave cavity mirror 6. S8. As shown in h in Figure 2, remove the aluminum etching stop layer using a wet method; S9. As shown in Figure 2i, a 1000℃ high-temperature hot air gun is used to blow the center of the "U"-shaped configuration area, so that the second plane glass 5-2 melts to form a smooth concave mirror surface, thus making a concave mirror; when making the concave mirror, the radius of the concave cavity mirror 6 is adjusted by adjusting the wind speed of the hot air gun. S10. As shown in Figure 2j, silicon oxide and tantalum pentoxide films are alternately deposited on the concave cavity mirror 6 to form an ultra-low loss optical multilayer dielectric film. The optical multilayer dielectric film is a semi-transparent film at the laser center wavelength, and the reflectivity of the semi-transparent film at the laser center wavelength is 30-70%. The ultra-low loss requires a loss rate of <10 ppm. The semi-transparent film is a high-reflectivity film for light wavelengths other than the laser center wavelength. Then, the mirror surface is polished sequentially using single-sided polishing and chemical mechanical polishing techniques to obtain an ultra-high reflectivity cavity mirror. The ultra-high reflectivity requirements are: reflectivity ≥99.99% and loss rate <10 ppm. S11. As shown in Figure 2k, the cylindrical glass tube 4 is bonded to the second planar glass 5-2 / concave cavity mirror 6 without adhesive. S12. As shown in Figure 3l, the wire of the annular piezoelectric ceramic sheet 1 passes through the through hole on the first planar glass 5-1, leaving a length for welding / conductive bonding between the wire and the annular piezoelectric ceramic sheet 1 at the cavity end. The glass is slowly heated to above the glass softening temperature in an inert atmosphere or clean air, allowing the glass material of the first planar glass 5-1 to flow and wet the hole wall and the wire, filling the gap and removing air bubbles. The temperature is maintained until the morphology of the first planar glass 5-1 is stable. The first planar glass 5-1 is bonded to one side of the annular piezoelectric ceramic sheet 1, and the planar cavity mirror 2 is attached to the other side of the annular piezoelectric ceramic sheet 1. An ultra-low loss optical multilayer dielectric film is deposited on the planar cavity mirror 2. This dielectric film is semi-transparent to the laser center wavelength and highly reflective to other wavelengths. The reflectivity of the semi-transparent film at the laser center wavelength is 30-70%, and the required loss rate is <10 ppm. The semi-transparent film is highly reflective to wavelengths other than the laser center wavelength, and the reflectivity requirement for the high-reflective film is ≥99.99%, and the loss rate is <10 ppm.

[0038] The first planar glass 5-1, the second planar glass 5-2, and the cylindrical glass tube 4 mentioned above are all made of ultra-low expansion coefficient glass, and the expansion coefficient of ultra-low expansion coefficient glass at room temperature is less than 1×10-8K-1.

[0039] S13. As shown in Figure 3m, an ultra-low loss optical multilayer dielectric film is formed on the mirror surface of the planar cavity mirror 2 by alternating vapor deposition of silicon oxide film and tantalum pentoxide film. Then, the mirror surface of the planar cavity mirror 2 is polished by single-sided polishing and chemical mechanical polishing techniques in sequence to obtain a cavity mirror with ultra-high reflectivity. S14. As shown in Figure 3n, under a high vacuum environment, the combination of the first planar glass 5-1 / planar cavity mirror 2 with the cylindrical glass tube 4 and the second planar glass 5-2 / concave cavity mirror 6 is used to obtain the Fabry-Perot cavity module. The fabrication of the atomic gas chamber module includes the following steps: S15. As shown in Figure 3o, spin-coat a layer of photoresist onto the silicon wafer and photolithographically print the atomic gas chamber pattern. S16. As shown in Figure 3p, deposit an aluminum etching stop layer on the silicon wafer. S17. As shown in q in Figure 3, perform wet removal of resist and aluminum; leave an aluminum etching stop layer in the periphery of the silicon wafer. S18. As shown in Figure 3r, deep reactive ion etching is used on the silicon wafer until the silicon wafer is penetrated to form a cylindrical silicon gas chamber wall 7. The aluminum etching stop layer is then removed by wet etching. Figure 3r shows a cross-sectional view of the cylindrical silicon gas chamber wall 7 after etching is completed. S19. As shown in Figure 4s, the planar borosilicate glass 9 is bonded to the lower end of the cylindrical silicon gas chamber wall 7. S20. As shown in Figure 4t, an alkali metal compound is filled into the atomic gas chamber 8 formed by bonding the planar borosilicate glass 9 to the silicon wafer. S21. As shown in Figure 4, the second planar glass 5-2 of the Fabry-Perot cavity module made in step S14 is bonded to the upper end of the cylindrical silicon gas chamber wall 7. S22. As shown in Figure 4v, alkali metal atom gas is obtained by irradiating the gas chamber with ultraviolet light, and a dual-cavity coupled integrated structure frequency stabilizer based on Fabry-Perot cavity is fabricated.

[0040] After the Fabry-Perot cavity module is sealed and bonded, a vacuum chamber 3 needs to be formed by evacuation.

[0041] In summary, the fabrication process of the Fabry-Perot cavity module includes the following sub-steps; Step 2.1: Deposit an antireflective coating with the laser center wavelength on one plane of the second planar glass 5-2; In step 2.2, the outer contour of the concave cavity mirror 6 is photolithographically etched on another plane of the second planar glass 5-2; Step 2.3: Photolithographically create a concave target pattern on the outer contour of the concave cavity mirror 6; Step 2.4: Use a hot air gun to blow the center of the concave mirror to melt the glass and form a smooth concave cavity mirror 6. When the glass is melting, adjust the radius of the concave cavity mirror 6 by adjusting the air speed of the hot air gun. Step 2.5: Alternately vapor-deposit silicon oxide and tantalum pentoxide to form an optical multilayer dielectric film on the concave cavity mirror 6; Step 2.6: The concave cavity mirror 6 is mirror polished by single-sided polishing and chemical mechanical polishing techniques in sequence to obtain a concave cavity mirror 6 with ultra-high reflectivity, wherein the high reflectivity is: reflectivity ≥ 99.99%.

[0042] As described in the second aspect of the present invention, step 4, fabricating the cylindrical silicon gas chamber wall 7, includes the following sub-steps: Step 4.1: Spin-coat a layer of photoresist onto the silicon wafer and use photolithography to obtain the air cell pattern; Step 4.2: Ion etching is used to penetrate the silicon wafer 1, forming a cylindrical silicon gas chamber wall 7.

[0043] As described in the second aspect of the present invention, step 5 includes: selecting a predetermined alkali metal compound material and placing it into the atomic gas chamber 8 according to the laser center wavelength.

[0044] This invention provides several frequency stabilization methods, including the following: The 778.1 nm two-photon transition frequency stabilization scheme of the Fabry-Perot cavity dual-cavity coupled integrated structure frequency stabilizer is described below. Figure 5As shown, it includes a tunable external cavity semiconductor laser 2-1, an optical isolator 2-2, a phase modulator 2-3, a photodetector 2-4, an optical beam splitter 2-5, a frequency stabilizer based on a Fabry-Perot cavity dual-cavity coupled integrated structure 2-6, a 10 nm filter 2-7, a photomultiplier tube 2-8, a frequency locking module 2-9, and a frequency locking module 2-10.

[0045] After the laser output from the 778.1 nm tunable external cavity semiconductor laser 2-1, it passes through an optical isolator 2-2, a phase modulator 2-3, an optical beam splitter 2-5, a frequency stabilizer 2-6 based on a Fabry-Perot cavity dual-cavity coupled integrated structure, and a 10 nm filter 2-7. The optical isolator 2-2 is used to isolate reflected light, the phase modulator 2-3 is used to adjust the phase of the laser input to the Fabry-Perot cavity module, the optical beam splitter 2-5 is used to split the laser beam and refract the reflected light from the Fabry-Perot cavity, and the 10 nm filter 2-7 is used to filter the 420 nm two-photon transition fluorescence signal and the reflected 778.1 nm laser to achieve rubidium-87 atom two-photon transition. The 420 nm two-photon transition fluorescence signal is detected by a photomultiplier tube 2-8.

[0046] If the center wavelength of the tunable external cavity semiconductor laser is around 795 nm, the frequency stabilizer based on the dual-cavity coupled integrated structure of the Fabry-Perot cavity is redesigned and optimized to adjust the center wavelength of the Fabry-Perot cavity to around 795 nm. The atomic gas chamber 8 is filled with rubidium 85 atoms and a saturated absorption optical path is used to lock the output frequency on the D1 transition line of rubidium atoms, thus obtaining a stable 795 nm laser output.

[0047] If the center wavelength of the tunable external cavity semiconductor laser is around 780 nm, the frequency stabilizer based on the dual-cavity coupled integrated structure of the Fabry-Perot cavity is redesigned and optimized to adjust the resonant frequency of the Fabry-Perot cavity to around 780 nm. The atomic gas chamber 8 is filled with rubidium 85 atoms and a saturated absorption optical path is used to lock the output frequency on the D2 transition line of rubidium atoms, thus obtaining a stable 780 nm laser output.

[0048] If the center wavelength of the tunable external cavity semiconductor laser is around 894 nm, the frequency stabilizer based on the Fabry-Perot cavity dual-cavity coupled integrated structure is redesigned and optimized to adjust the resonant frequency of the Fabry-Perot cavity to around 894 nm. The atomic gas chamber 8 is filled with cesium-133 atoms and a saturated absorption optical path is used to lock the output frequency on the D1 transition line of cesium atoms, thus obtaining a stable 894 nm laser output.

[0049] If the center wavelength of the tunable external cavity semiconductor laser is around 852 nm, the frequency stabilizer based on the Fabry-Perot cavity dual-cavity coupled integrated structure is redesigned and optimized to adjust the resonant frequency of the Fabry-Perot cavity to around 852 nm. The atomic gas chamber 8 is filled with cesium-133 atoms and a saturated absorption optical path is used to lock the output frequency on the D2 transition line of cesium atoms, thus obtaining a stable 852 nm laser output.

[0050] If the center wavelength of the tunable external cavity semiconductor laser is around 770 nm, the frequency stabilizer based on the Fabry-Perot cavity dual-cavity coupled integrated structure is redesigned and optimized to adjust the resonant frequency of the Fabry-Perot cavity to around 770 nm. The atomic gas chamber 8 is filled with potassium 39 atoms and a saturated absorption optical path is used to lock the output frequency on the potassium atom D1 transition line, thus obtaining a stable 770 nm laser output.

[0051] If the center wavelength of the tunable external cavity semiconductor laser is around 766 nm, the frequency stabilizer based on the Fabry-Perot cavity dual-cavity coupled integrated structure is redesigned and optimized to adjust the resonant frequency of the Fabry-Perot cavity to around 766 nm. The atomic gas chamber 8 is filled with potassium 39 atoms and a saturated absorption optical path is used to lock the output frequency on the potassium atom D2 transition line, thus obtaining a stable 766 nm laser output.

[0052] It will be apparent to those skilled in the art that the embodiments of the present invention are not limited to the details of the exemplary embodiments described above, and that the embodiments of the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the embodiments of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the embodiments of the present invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations falling within the meaning and scope of equivalents of the claims be encompassed within the embodiments of the present invention. The terms "first," "second," etc., are used to denote names and do not indicate any particular order.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and are not intended to limit them. Although the embodiments of the present invention have been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the embodiments of the present invention should not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency stabilizer based on a Fabry-Perot cavity dual-cavity coupled integrated structure, characterized in that, The dual-cavity coupled integrated structure frequency stabilizer includes: a Fabry-Perot cavity module and an atomic gas chamber module, wherein the Fabry-Perot cavity module is located above the atomic gas chamber module; The Fabry-Perot cavity module includes: a first planar glass, a second planar glass, a cylindrical glass tube, an annular piezoelectric ceramic sheet, a planar cavity mirror, a vacuum chamber, and a concave cavity mirror; The first planar glass is sealed to the upper end of the cylindrical glass tube, and the second planar glass is sealed to the lower end of the cylindrical glass tube. A cavity is formed by the inner side of the first planar glass, the upper side of the second planar glass, and the inner side of the cylindrical glass tube. Within this cavity, from bottom to top, are the concave cavity mirror, the vacuum chamber, the planar cavity mirror, and the annular piezoelectric ceramic sheet. The upper side of the annular piezoelectric ceramic sheet is sealed to the inner side of the first planar glass; the lower side of the annular piezoelectric ceramic sheet is sealed to the upper side of the planar cavity mirror. The vacuum chamber is formed by the lower side of the planar cavity mirror, the inner side of the cylindrical glass tube, and the concave surface of the concave cavity mirror. The concave surface of the concave cavity mirror faces the vacuum chamber, and the planar side of the concave cavity mirror is sealed to the upper side of the second planar glass. The atomic gas chamber module includes: a cylindrical silicon gas chamber wall, a second planar glass, a piece of planar borosilicate glass, and an atomic gas chamber. The second planar glass is shared by the Fabry-Perot cavity module and the atomic gas chamber module; The upper end of the cylindrical silicon gas chamber wall is sealed to the lower side of the second planar glass, and the lower end of the cylindrical silicon gas chamber wall is sealed to the inner side of a planar borosilicate glass. An atomic gas chamber is formed by the inner side of the cylindrical silicon gas chamber wall, the lower side of the second planar glass, and the inner side of the planar borosilicate glass. A predetermined alkali metal compound material is placed in the atomic gas chamber. The laser wavelength absorbed or emitted by the predetermined alkali metal compound material corresponds to the laser center wavelength stabilized by the Fabry-Perot cavity module.

2. The dual-cavity coupled integrated frequency stabilizer as described in claim 1, characterized in that, The first planar glass is coated with an antireflective film targeting the center wavelength of the incident laser beam in the direction facing the incident laser beam; the second planar glass is coated with an antireflective film targeting the center wavelength of the incident laser beam in the direction facing the atomic gas chamber; the transmittance of the antireflective film is ≥90%, and the first planar glass, the cylindrical glass tube, and the second planar glass are all made of ultra-low expansion coefficient glass, which has an expansion coefficient of less than 1×10 at room temperature. -8 K -1 .

3. The dual-cavity coupled integrated frequency stabilizer as described in claim 1, characterized in that, In the Fabry-Perot cavity module, both the planar and concave cavity mirrors are coated with a semi-permeable film corresponding to the center wavelength of the incident laser beam. The semi-permeable film is arranged in the opposite direction of the planar and concave cavity mirrors. The reflectivity of the semi-permeable film at the center wavelength of the laser is 30-70%, and the loss rate is <10 ppm. For light wavelengths other than the center wavelength of the laser, the semi-permeable film is a high-reflectivity film with a reflectivity ≥99.99% and a loss rate <10 ppm. The semi-permeable film is composed of alternating stacks of silicon oxide and tantalum pentoxide.

4. The dual-cavity coupled integrated frequency stabilizer as described in claim 1, characterized in that, The sealing connection methods for the various parts of the Fabry-Perot cavity module and the atomic gas chamber module include: bonding, welding and bonding.

5. The dual-cavity coupled integrated frequency stabilizer as described in claim 1, characterized in that, The electrode leads of the annular piezoelectric ceramic sheet are led out from inside the Fabry-Perot cavity module through the first planar glass.

6. The dual-cavity coupled integrated frequency stabilizer as described in claim 1, characterized in that, The alkali metal of the predetermined alkali metal compound material placed in the atomic gas chamber is one of rubidium, potassium, or cesium.

7. A method for fabricating a dual-cavity coupled integrated frequency stabilizer based on a Fabry-Perot cavity, characterized in that, The method is used to prepare a dual-cavity coupled integrated structure frequency stabilizer based on a Fabry-Perot cavity as described in any one of claims 1-6, comprising: Step 1: Fabricate a planar cavity mirror on the first planar glass; including: An antireflective coating targeting the center wavelength of the incident laser beam is deposited on the outer surface of the first planar glass. An annular piezoelectric ceramic sheet is bonded to the inner surface of the first planar glass. A planar cavity mirror is bonded to the other side of the annular piezoelectric ceramic sheet. Multiple layers of silicon oxide film and tantalum pentoxide film are alternately deposited on the cavity mirror surface of the planar cavity mirror to form a semi-permeable film targeting the incident laser beam. Step 2: Fabricate a concave cavity mirror on the second planar glass; Step 3: The first planar glass, the cylindrical glass tube, the second planar glass, the annular piezoelectric ceramic sheet, the planar cavity mirror, and the concave cavity mirror are connected in a sealed manner to form a Fabry-Perot cavity module; Step 4: Fabricate the cylindrical silicon gas chamber wall; Step 5: The second planar glass, the cylindrical silicon gas chamber wall, and a piece of planar borosilicate glass are connected in a sealed manner to form an atomic gas chamber module; and a predetermined alkali metal compound material is placed inside the atomic gas chamber. Step 6: Use ultraviolet light to irradiate the atomic gas chamber to generate gaseous alkali metal atoms, and fabricate a micro dual-cavity coupled integrated structure frequency stabilizer.

8. The method as described in claim 7, characterized in that, Step 2 includes the following sub-steps; Step 2.1: Deposit an antireflective coating on one plane of the second planar glass, targeting the center wavelength of the incident laser beam; Step 2.2: The outer contour of the concave cavity mirror is photolithographically formed on another plane of the second planar glass; Step 2.3: Photolithographically create the target pattern of the concave cavity mirror on the surface of the outer contour of the concave cavity mirror; Step 2.4: Use a hot air gun to blow the center of the target pattern of the concave cavity mirror to melt the glass and make a smooth concave cavity mirror surface. While the glass is melting, adjust the mirror cavity radius of the concave mirror by adjusting the air speed of the hot air gun. Step 2.5: Alternately deposit silicon oxide film and tantalum pentoxide film on the concave cavity mirror to form a semi-permeable film for the center wavelength of the incident laser beam; Step 2.6: The concave cavity mirror is polished by single-sided polishing and chemical mechanical polishing techniques in sequence to obtain a concave cavity mirror with high reflectivity, wherein high reflectivity means reflectivity ≥99.99%.

9. The method as described in claim 7, characterized in that, Step 4, fabricating the cylindrical silicon gas chamber wall, includes the following sub-steps: Step 4.1: Spin-coat a layer of photoresist onto the silicon wafer and obtain the air cell pattern through photolithography; Step 4.2: Ion etching is used on the silicon wafer until the silicon wafer is penetrated to form a cylindrical silicon gas chamber wall.

10. The method as described in claim 7, characterized in that, Step 5 includes: selecting a predetermined alkali metal compound material and placing it into the atomic gas chamber based on the center wavelength of the incident laser beam.

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