An ultrastable cavity with optical fiber as cavity

Abstract

The present invention belongs to the field of laser frequency stabilization technology and discloses an ultrastable cavity using optical fiber as a cavity. The cavity comprises an optical fiber cavity component, which includes an optical fiber, with both ends of the optical fiber coated with a highly reflective coating, and optical fiber connectors are provided at both ends of the optical fiber along its length. The ultrastable cavity of the present invention utilizes optical fiber and an optical fiber optical path, is independent of vacuum, and effectively reduces the size of the ultrastable cavity. It can eliminate the dependence of the PDH frequency stabilization system on the polarization characteristics of the optical path, eliminate the need for complex cavity mode coupling, avoid tedious mode matching and optical path adjustment, and simplify operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser frequency stabilization, and in particular relates to an ultra-stable cavity using an optical fiber as a cavity. Background Art

[0002] Pound-Drever-Hall (PDH) frequency stabilization technology is an active frequency stabilization technology and is one of the best performing methods in current laser frequency stabilization systems.

[0003] Ultrastable cavities are primarily used in PDH frequency stabilization systems. Light to be frequency-stabilized is injected into the cavity. The laser frequency is scanned while the reflected light intensity from the cavity is monitored. The minimum reflected light intensity can be detected, and the PDH frequency stabilization system can then stabilize the laser frequency at the point where the reflected light intensity is minimized. To ensure mode stability, the cavity is typically insulated and vacuum-treated.

[0004] Existing ultrastable cavities use a highly sealed vacuum chamber to maintain their internal vacuum, resulting in a relatively large volume. Furthermore, because spatial light propagates virtually unrestricted, its transverse mode can be any, while only one transverse mode can fully match the ultrastable cavity. To ensure that the transverse mode of the spatial light matches that of the ultrastable cavity, a specially designed optical path is required to shape the spatial light. During cavity mode matching, only light whose transverse and longitudinal modes simultaneously match the ultrastable cavity mode can pass through the cavity. This makes successful mode matching difficult to visualize, and to some extent, complicates optical path adjustment.

[0005] like Figure 1 As shown, the existing ultra-stable cavity optical path is entirely spatial light. To ensure that the incident light can be coupled into the ultra-stable cavity, it is necessary to select a suitable collimator 1 and ensure that the distance between the collimator 1 and the cavity mirror 5 is just the right distance. In most cases, a single collimator 1 cannot guarantee cavity mode coupling. It is necessary to add a lens or lens group 2, a polarization beam splitter prism 3, and a photodetector 6 to the optical path, and ensure that the distance between the lens or lens group 2 and the cavity mirror 5 is appropriate. At the same time, after ensuring that the collimator 1 and the lens or lens group 2 are in the correct position, it is also necessary to adjust the reflector 4 to ensure that the spatial light is completely incident on the cavity mirror 5, ensuring that the base film transmittance reaches the highest.

[0006] In summary, existing ultrastable cavities rely on a vacuum environment, are large in size, and the mode matching and spatial optical path adjustment are cumbersome, time-consuming, and labor-intensive. Summary of the Invention

[0007] To address the above problems, the present invention provides an ultrastable cavity with an optical fiber as the cavity, which adopts the following technical solutions:

[0008] An ultrastable cavity with an optical fiber as a cavity comprises an optical fiber cavity component, wherein the optical fiber cavity component comprises an optical fiber, both ends of the optical fiber are plated with high reflection films, and both ends of the optical fiber in the length direction are provided with optical fiber connectors.

[0009] Furthermore, it also includes installing a fixing component and a heat-insulating component;

[0010] The optical fiber is arranged inside the mounting and fixing component, both ends of the optical fiber in the length direction extend to the outside of the mounting and fixing component, the optical fiber connector is fixedly connected to the mounting and fixing component, and the heat-insulating component is arranged on the mounting and fixing component;

[0011] The optical fiber cavity component further includes a protective layer, which is coated on the outside of the optical fiber.

[0012] Furthermore, both ends of the optical fiber in the length direction are sleeved with connecting posts, and one end of each connecting post close to the protective layer is fixedly connected to the protective layer.

[0013] Furthermore, the installation and fixing component includes a fixing seat and a cavity fixing frame;

[0014] In which, the cavity fixing frame has a accommodating cavity, the fixing seat and the optical fiber cavity component are both arranged in the accommodating cavity, the fixing seat is covered on the outside of the protective layer, the insulation component is covered on the outside of the cavity fixing frame, and the connecting column is detachably connected to the fixing seat through an optical fiber connector.

[0015] Furthermore, the optical fiber connector includes an optical fiber flange and an adapter;

[0016] In which, the optical fiber flange includes a flange plate, a stud and an elastic sleeve, and the two side surfaces of the flange plate parallel to the fixing seat are provided with bosses, and the flange plate and the bosses on the two side surfaces are provided with penetrating internal threaded holes, the external thread on the outer side of the stud is threadedly connected to the internal threaded hole, the stud is axially provided with a second through hole, the elastic sleeve is arranged in the second through hole, and the elastic sleeve is sleeved on the connecting column; the flange plate is detachably connected to the adapter, and the adapter is detachably connected to the fixing seat.

[0017] Furthermore, the fixing seat includes an upper fixing block and a lower fixing block;

[0018] The top surface of the upper fixing block and the bottom surface of the lower fixing block are both provided with grooves along the length direction of the protective layer. The grooves of the upper fixing block and the lower fixing block form a cavity matching the protective layer. The protective layer is located in the cavity. The grooves of the upper fixing block and the lower fixing block are both provided with baffles at both ends of the protective layer; the upper fixing block, the lower fixing block and the adapter are detachably connected.

[0019] Furthermore, the adapter includes a connecting plate, a concave platform is provided at the center of the outer side surface of the connecting plate, a positioning hole is provided at the center of the concave platform, the flange plate is located in the concave platform, and the boss on the inner side surface of the flange plate is located in the positioning hole;

[0020] The flange plate is provided with a first countersunk hole at the corner of the outer side of the boss, and the interior of the recessed platform is provided with a third through hole corresponding to the position of the first countersunk hole along the circumference of the positioning hole;

[0021] The upper fixing block and the lower fixing block are both provided with threaded blind holes on two side surfaces perpendicular to the center line of the optical fiber, and a plurality of fourth through holes are provided on the connecting plate, the fourth through holes on the upper part of the connecting plate correspond to the positions of the threaded blind holes on the upper fixing block, and the fourth through holes on the lower part of the connecting plate correspond to the positions of the threaded blind holes on the lower fixing block.

[0022] Furthermore, the upper fixing block is provided with a first blind hole at a corner of the top side parallel to the centerline of the optical fiber, and the lower fixing block is provided with a second blind hole at a corner of the bottom side parallel to the centerline of the optical fiber.

[0023] Furthermore, mounting holes are provided on the four sides and the top surface of the cavity fixing frame, the thermal insulation component includes a heating plate and an insulation layer, a heating plate is provided on each side of the fixing seat, and the insulation layer is embedded in each mounting hole.

[0024] Furthermore, the fixing seat is fixed in the accommodating cavity of the cavity fixing frame, and there is a gap between the fixing seat and the cavity fixing frame.

[0025] Beneficial effects of the present invention:

[0026] The ultrastable cavity of the present invention adopts optical fiber and uses an optical fiber optical path, is independent of vacuum, effectively reduces the volume of the ultrastable cavity, can get rid of the dependence of the PDH frequency stabilization system on the polarization characteristics of the optical path, does not need to perform complex cavity mode coupling, avoids tedious mode matching and optical path adjustment, and is easy to operate.

[0027] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 A schematic diagram of the optical path structure of an ultrastable cavity according to the prior art is shown;

[0030] Figure 2 An axonometric diagram of an ultrastable cavity using an optical fiber as a cavity according to an embodiment of the present invention is shown;

[0031] Figure 3 A schematic structural diagram of an optical fiber cavity component according to an embodiment of the present invention is shown;

[0032] Figure 4 It shows a schematic structural diagram of the installation and fixing component according to an embodiment of the present invention;

[0033] Figure 5 A schematic diagram of the installation of a protective layer and mounting and fixing components according to an embodiment of the present invention is shown;

[0034] Figure 6 A schematic structural diagram of an optical fiber flange according to an embodiment of the present invention is shown;

[0035] Figure 7 It shows a schematic structural diagram of a fixing base according to an embodiment of the present invention;

[0036] Figure 8 It shows a schematic structural diagram of an adapter according to an embodiment of the present invention;

[0037] Figure 9 It shows a schematic structural diagram of a cavity fixing frame according to an embodiment of the present invention;

[0038] Figure 10 A schematic diagram of the installation of a fixing base and a heating plate according to an embodiment of the present invention is shown;

[0039] Figure 11 A schematic structural diagram of a shock-absorbing plate according to an embodiment of the present invention is shown;

[0040] Figure 12A schematic diagram of the optical path structure of an ultrastable cavity using an optical fiber as a cavity according to an embodiment of the present invention is shown.

[0041] Figure: 1, collimator; 2, lens group; 3, polarization beam splitter prism; 4, reflector; 5, cavity mirror; 6, photodetector; 7, optical fiber cavity component; 8, mounting and fixing component; 9, thermal insulation component; 10, optical fiber; 11, optical fiber connector; 12, protective layer; 13, first through hole; 14, high reflective film; 15, connecting column; 16, fixing seat; 17, cavity fixing frame; 18, accommodating cavity; 19, optical fiber flange; 20, adapter; 21, flange plate; 22, stud; 23, elastic sleeve; 24, boss; 25, second through hole Hole; 26, notch; 27, upper fixing block; 28, lower fixing block; 29, groove; 30, baffle; 31, threaded blind hole; 32, connecting plate; 33, recessed platform; 34, positioning hole; 35, first countersunk hole; 36, third through hole; 37, fourth through hole; 38, first blind hole; 39, second blind hole; 40, mounting hole; 41, heating plate; 42, insulation layer; 43, first threaded hole; 44, base; 45, second countersunk hole; 46, shock-absorbing plate; 47, second threaded hole; 48, third countersunk hole; 49, fiber optic circulator. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0043] It should be noted that the terms "first", "second" etc. in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the application described herein. In this application, the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "center", "vertical", "horizontal", "lateral", "longitudinal" etc. are based on the directions or positional relationships shown in the accompanying drawings.

[0044] The present invention provides an ultrastable cavity with an optical fiber as a cavity, which is independent of vacuum, reduces the volume of the device, avoids tedious mode matching and optical path adjustment, and is easy to operate.

[0045] like Figure 2 As shown, an ultra-stable cavity with an optical fiber as the cavity includes an optical fiber cavity component 7, a mounting and fixing component 8 and a heat preservation component 9.

[0046] The optical fiber cavity component 7 is arranged inside the mounting and fixing component 8, and the optical fiber cavity component 7 includes an optical fiber 10. Both ends of the optical fiber 10 in the length direction extend to the outside of the mounting and fixing component 8. As an external interface, both end faces of the optical fiber (10) are plated with a high-reflection film (14), and both ends of the optical fiber (10) in the length direction are provided with an optical fiber connector (11), and the optical fiber connector 11 is fixedly connected to the mounting and fixing component 8.

[0047] The heat preservation component 9 is arranged on the mounting and fixing component 8 and is used to heat and keep the optical fiber 10 warm. The optical signal input end is connected to the optical fiber 10 through the optical fiber connector 11 so that the cavity can be used as an ultra-stable cavity.

[0048] like Figure 3 As shown, for example, the optical fiber cavity component 7 further includes a protective layer 12, which is coated on the outside of the optical fiber 10. The protective layer 12 is used to protect the optical fiber 10 from deformation. For example, the material of the protective layer 12 can be quartz glass, microcrystalline glass, zero expansion glass (Ultra-Low Expansion, ULE) or ceramics.

[0049] For example, the optical fiber 10 is a single-mode optical fiber, and the length of the optical fiber 10 is determined by the required free spectral range (FSR), as follows:

[0050] vFSR=C / 2nL

[0051] Wherein, vFSR represents the free spectral range, C represents the speed of light, n represents the core refractive index of the optical fiber 10, and L represents the length of the optical fiber 10.

[0052] For example, the protective layer 12 is cylindrical, and a first through hole 13 is axially arranged at the center of the protective layer 12. The optical fiber 10 is arranged in the first through hole 13. The two ends of the optical fiber 10 in the length direction are located outside the protective layer 12. High-reflection films 14 are applied on both end faces of the optical fiber 10.

[0053] like Figure 3 As shown, for example, both ends of the optical fiber 10 in the length direction are provided with connecting posts 15, and one end of each connecting post 15 close to the protective layer 12 is fixedly connected to the protective layer 12. For example, the material of the connecting post 15 can be ceramic, or quartz glass, microcrystalline glass or zero expansion glass (Ultra-Low Expansion, ULE).

[0054] Pass the optical fiber 10 through the first through hole 13 in the center of the protective layer 12, then pass both ends of the optical fiber 10 through the center of the connecting column 15, polish the end face of the connecting column 15 to make the optical fiber 10 and the end face of the connecting column 15 smooth, embed the connecting column 15 into the protective layer 12 and perform a firm bond, and finally plate a high-reflectivity high-reflection film 14 on the polished end face of the optical fiber 10 to obtain the optical fiber cavity component 7.

[0055] For example, the high-reflection film 14 is not applied to the two end faces of the optical fiber 10. By irradiating the two ends of the optical fiber 10 with ultraviolet light, a fiber Bragg grating Fabry-Perot cavity is obtained. Specifically, ultraviolet light is irradiated to the two ends of the optical fiber 10, so that the refractive index in the optical fiber 10 changes periodically, and a fiber Bragg grating (FBG) is formed inside the optical fiber 10. The central wavelength of the fiber Bragg grating is determined to be the wavelength to be locked, and a fiber Bragg grating Fabry-Perot cavity is obtained, which is used as an ultra-stable cavity.

[0056] like Figure 4 As shown, for example, the installation and fixing component 8 includes a fixing seat 16 and a cavity fixing frame 17, wherein the cavity fixing frame 17 has an accommodating cavity 18, the fixing seat 16 and the optical fiber cavity component 7 are both arranged in the accommodating cavity 18, the fixing seat 16 is covered on the outside of the protective layer 12, the insulation component 9 is covered on the outside of the cavity fixing frame 17, and the connecting columns 15 at both ends of the length direction of the optical fiber 10 are detachably connected to the fixing seat 16 through the optical fiber connector 11.

[0057] For example, the fixing seat 16 is made of Invar, which has good ductility and a small linear expansion coefficient, and can better protect the protective layer 12 .

[0058] like Figure 5 As shown, for example, the optical fiber connector 11 includes an optical fiber flange 19 and an adapter 20, wherein Figure 6 As shown, the fiber flange 19 includes a flange plate 21, a stud 22, and an elastic sleeve 23. Bosses 24 are provided at the center of both sides of the square flange plate 21 parallel to the fixing base 16. Internally threaded holes are provided through the flange plate 21 and the bosses 24 on both sides. External threads matching the internally threaded holes are provided on the outer sides of the stud 22, which are threadedly connected to the internally threaded holes. A second through hole 25 is provided axially along the stud 22, and the elastic sleeve 23 is disposed within the second through hole 25. The elastic sleeve 23 is sleeved onto the connecting post 15. The inner diameter of the elastic sleeve 23 matches the outer diameter of the connecting post 15, allowing the optical fiber 10 wrapped by the connecting post 15 to be aligned.

[0059] The flange plate 21 is detachably connected to the adapter 20, and the adapter 20 is detachably connected to the fixing base 16. For example, the stud 22 is provided with notches 26 at both ends in the length direction.

[0060] like Figure 4 and Figure 7 As shown, for example, the fixing seat 16 and the accommodating cavity 18 are both square, and the fixing seat 16 includes an upper fixing block 27 and a lower fixing block 28. The top surface of the upper fixing block 27 and the bottom surface of the lower fixing block 28 are both provided with semicircular grooves 29 along the length direction of the protective layer 12. The semicircular grooves 29 of the upper fixing block 27 and the lower fixing block 28 form a circular cavity matching the protective layer 12. The protective layer 12 is located in the cavity. The grooves 29 of the upper fixing block 27 and the grooves 29 of the lower fixing block 28 are both provided with semicircular ring baffles 30 at both ends of the protective layer 12. The baffles 30 position the protective layer 12.

[0061] The upper fixing block 27 and the lower fixing block 28 are detachably connected to the adapter 20. For example, the upper fixing block 27 and the lower fixing block 28 are provided with threaded blind holes 31 on two side surfaces perpendicular to the center line of the optical fiber 10. For example, two threaded blind holes 31 are provided on each side surface. The specification of the threaded blind holes 31 is M4. The bolts pass through the adapter 20 and are threadedly connected to the threaded blind holes 31, so that the adapter 20 is detachably connected to the upper fixing block 27 and the lower fixing block 28.

[0062] like Figure 8 As shown, for example, the adapter 20 includes a square connecting plate 32, a square recess 33 is provided at the center of the outer side surface of the connecting plate 32, a positioning hole 34 is provided at the center of the recess 33, the flange plate 21 is located in the recess 33, and the boss 24 on the inner side surface of the flange plate 21 is located in the positioning hole 34, thereby realizing the positioning of the flange plate 21 and the connecting plate 32.

[0063] The flange plate 21 is provided with first countersunk holes 35 at the four corners on the outer side of the boss 24, and four third through holes 36 corresponding to the positions of the first countersunk holes 35 are provided inside the recess 33 along the circumference of the positioning hole 34. Bolts pass through the third through holes 36 and are connected to nuts to detachably connect the flange plate 21 and the connecting plate 32.

[0064] A plurality of fourth through holes 37 are provided on the connecting plate 32, wherein the two fourth through holes 37 on the upper portion of the connecting plate 32 correspond to the positions of the two threaded blind holes 31 on the upper fixing block 27, and the two fourth through holes 37 on the lower portion of the connecting plate 32 correspond to the positions of the two threaded blind holes 31 on the lower fixing block 28; bolts pass through the fourth through holes 37 and are threadedly connected to the threaded blind holes 31, so that the connecting plate 32 and the fixing seat 16 are detachably connected.

[0065] For example, the upper fixing block 27 is provided with a first blind hole 38 at the corner of the top side parallel to the center line of the optical fiber 10, and the lower fixing block 28 is provided with a second blind hole 39 at the corner of the bottom side parallel to the center line of the optical fiber 10. The first blind hole 38 and the second blind hole 39 are used to install the temperature control probe.

[0066] For example, four first blind holes 38 and four second blind holes 39 are provided, and the four first blind holes 38 and the four second blind holes 39 are symmetrically arranged along the center line of the optical fiber 10. Two first blind holes 38 are provided on each of the two parallel edges of the top side surface of the upper fixing block 27; the angle between the center line of the first blind hole 38 and the vertical side surface of the upper fixing block 27 is 45°; the bottom side surface of the lower fixing block 28 is provided with two first blind holes 38 on each of the two parallel edges, and the angle between the center line of the second blind hole 39 and the vertical side surface of the lower fixing block 28 is 45°, thereby ensuring uniform temperature control.

[0067] like Figure 9 As shown, for example, the cavity fixing frame 17 is square, and the four sides and the top surface of the cavity fixing frame 17 are provided with square mounting holes 40, and the heat preservation component 9 includes a heating plate 41 and a heat preservation layer 42, as shown in FIG. Figure 10 As shown, each side of the fixing seat 16 is provided with a heating plate 41. The shape of the heating plate 41 is set according to the side shape of the fixing seat 16. The heating plate 41 is provided with a avoidance hole to facilitate the installation of the optical fiber connector 11. Figure 2 As shown, a thermal insulation layer 42 is embedded in each mounting hole 40 .

[0068] For example, the heating plate 41 is made of a flexible printed circuit (FPC). Conventional methods, whether using air conditioning or a TEC (Technical Electron Cooler) for heat preservation, inevitably introduce fan vibration. Therefore, a flexible printed circuit (FPC) is used for heating, allowing the cavity to maintain a stable temperature above room temperature. The heating plate 41 is fixed to the surface of the mounting base 16 with adhesive, covering as large an area as possible.

[0069] For example, the thermal insulation layer 42 is made of EVA foam material with a relatively large number of cavities, which can be embedded in the cavity fixing frame 17 to completely block the internal cavity from contact with the outside world as much as possible.

[0070] For example, the cavity fixing frame 17 is made of stainless steel to ensure structural strength and stability.

[0071] For example, the fixing seat 16 is fixed to the center position of the accommodating cavity 18 of the cavity fixing frame 17, and a gap is provided between the fixing seat 16 and the cavity fixing frame 17, thereby reducing the contact between the fixing seat 16 and the cavity fixing frame 17 and reducing unnecessary heat transfer. For example, the four edges of the cavity fixing frame 17 parallel to the center line of the optical fiber 10 are provided with first threaded holes 43. For example, three first threaded holes 43 are provided on each edge of the cavity fixing frame 17 parallel to the center line of the optical fiber 10, and the specification of the first threaded holes 43 can be M4. The fixing seat 16 is threadedly connected to the first threaded holes 43 by bolts, and multiple bolts abut against the four edges of the fixing seat 16, thereby fixing the fixing seat 16 to the center of the accommodating cavity 18 of the cavity fixing frame 17, and providing a gap between the fixing seat 16 and the cavity fixing frame 17, thereby minimizing the contact between the fixing seat 16 and the cavity fixing frame 17.

[0072] like Figure 9 As shown, for example, a square base 44 is further provided at the bottom of the mounting and fixing component 8, the top of the base 44 is fixedly connected to the bottom of the cavity fixing frame 17, and second countersunk holes 45 are provided at the four corners of the base 44. For example, the specification of the second countersunk holes 45 is M6, and the base 44 is fixed to the optical platform by passing bolts through the second countersunk holes 45.

[0073] like Figure 2 As shown, for example, the ultra-stable cavity further includes a square shock-absorbing plate 46 , and the bottom of the base 44 is detachably connected to the shock-absorbing plate 46 . The ultra-stable cavity adopts a passive shock-absorbing method to isolate it from the outside world and achieve a shock-absorbing effect.

[0074] For example, the shock-absorbing plate 46 is made of marble. Since marble has a uniform structure and completely eliminates internal stress, it is not easy to deform and has excellent shock-absorbing performance.

[0075] like Figure 11 As shown, for example, the shock absorbing plate 46 is provided with a second threaded hole 47 at a position corresponding to the second countersunk hole 45 of the base 44. For example, the specification of the second threaded hole 47 is M6. The shock absorbing plate 46 is fixedly connected to the base 44 by a bolt passing through the second countersunk hole 45 and threadedly connected to the second threaded hole 47.

[0076] like Figure 11 As shown, for example, the vibration-absorbing plate 46 is further provided with a plurality of third countersunk holes 48 , for example, six third countersunk holes 48 are provided, and the vibration-absorbing plate 46 is fixed to the optical platform by passing bolts through the third countersunk holes 48 .

[0077] like Figure 12As shown, when the ultra-stable cavity of the present invention is in use, the optical signal input end is connected to the optical fiber 10 through the optical fiber flange 19 to be used as an ultra-stable cavity, the a end of the optical fiber circulator 49 is connected to the optical signal input end, the b end of the optical fiber circulator 49 is connected to one of the optical fiber flanges 19, and the c end of the optical fiber circulator 49 is connected to the photodetector 6, and it can be used by passing light. The optical fiber 10 is a solid structure, which can eliminate the dependence of the ultra-stable cavity on vacuum. Being separated from the vacuum cavity can effectively reduce the volume of the ultra-stable cavity. Using the optical fiber circulator 49 to monitor the return light can get rid of the dependence of the PDH system on the polarization characteristics of the optical path. Using the optical fiber optical path, there is no need to perform complex cavity mode coupling.

[0078] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultrastable cavity with an optical fiber as the cavity, characterized in that: The optical fiber cavity component (7) includes an optical fiber (10), both ends of the optical fiber (10) are coated with a high-reflection film (14), and both ends of the optical fiber (10) in the longitudinal direction are provided with optical fiber connectors (11); Both ends of the optical fiber (10) in the longitudinal direction are sleeved with connecting posts (15), and one end of each connecting post (15) close to the protective layer (12) is fixedly connected to the protective layer (12); The optical fiber connector (11) comprises an optical fiber flange (19) and an adapter (20), wherein the optical fiber flange (19) comprises a flange plate (21), and the adapter (20) comprises a connecting plate (32), wherein a concave platform (33) is provided at the center of the outer side surface of the connecting plate (32), and a positioning hole (34) is provided at the center of the concave platform (33), wherein the flange plate (21) is located in the concave platform (33), and the boss (24) on the inner side surface of the flange plate (21) is located in the positioning hole (34); The flange plate (21) is provided with a first countersunk hole (35) at the corner outside the boss (24), and a third through hole (36) corresponding to the position of the first countersunk hole (35) is provided inside the recess (33) along the circumference of the positioning hole (34); The upper fixing block (27) and the lower fixing block (28) are both provided with threaded blind holes (31) on two side surfaces perpendicular to the center line of the optical fiber; a plurality of fourth through holes (37) are provided on the connecting plate (32); the fourth through holes (37) on the upper portion of the connecting plate (32) correspond to the positions of the threaded blind holes (31) on the upper fixing block (27); and the fourth through holes (37) on the lower portion of the connecting plate (32) correspond to the positions of the threaded blind holes (31) on the lower fixing block (28).

2. The ultrastable cavity with the optical fiber as the cavity according to claim 1, characterized in that: It also includes a mounting and fixing component (8) and a heat-insulating component (9); The optical fiber (10) is arranged inside the mounting and fixing component (8), both ends of the optical fiber (10) in the length direction extend to the outside of the mounting and fixing component (8), the optical fiber connector (11) is fixedly connected to the mounting and fixing component (8), and the heat-insulating component (9) is arranged on the mounting and fixing component (8); The optical fiber cavity component (7) further comprises a protective layer (12), wherein the protective layer (12) is coated on the outside of the optical fiber (10).

3. The ultrastable cavity with optical fiber as cavity according to claim 2, characterized in that: The mounting and fixing component (8) comprises a fixing seat (16) and a cavity fixing frame (17); The cavity fixing frame (17) has a receiving cavity (18), the fixing seat (16) and the optical fiber cavity component (7) are both arranged in the receiving cavity (18), the fixing seat (16) is covered on the outside of the protective layer (12), the heat-insulating component (9) is covered on the outside of the cavity fixing frame (17), and the connecting column (15) is detachably connected to the fixing seat (16) through an optical fiber connector (11).

4. The ultrastable cavity with optical fiber as cavity according to claim 3, characterized in that: The optical fiber flange (19) further includes a stud (22) and an elastic sleeve (23), and bosses (24) are provided on both sides of the flange plate (21) and the fixed seat (16), and the flange plate (21) and the bosses (24) on the two sides are provided with through internal threaded holes, and the external thread on the outer side of the stud (22) is threadedly connected to the internal threaded hole, and the stud (22) is provided with a second through hole (25) along the axial direction, and the elastic sleeve (23) is provided in the second through hole (25), and the elastic sleeve (23) is sleeved on the connecting column (15); the flange plate (21) is detachably connected to the adapter (20), and the adapter (20) is detachably connected to the fixed seat (16).

5. The ultrastable cavity with optical fiber as cavity according to claim 4, characterized in that: The fixing seat (16) includes an upper fixing block (27) and a lower fixing block (28); The top surface of the upper fixing block (27) and the bottom surface of the lower fixing block (28) are both provided with grooves (29) along the length direction of the protective layer (12); the grooves (29) of the upper fixing block (27) and the lower fixing block (28) form a cavity matching the protective layer (12); the protective layer (12) is located in the cavity; the grooves (29) of the upper fixing block (27) and the grooves (29) of the lower fixing block (28) are both provided with baffles (30) at both ends of the protective layer (12); the upper fixing block (27), the lower fixing block (28) and the adapter (20) are detachably connected.

6. The ultrastable cavity with the optical fiber as the cavity according to claim 5, characterized in that: The upper fixing block (27) is provided with a first blind hole (38) at an edge corner of the top side parallel to the center line of the optical fiber (10), and the lower fixing block (28) is provided with a second blind hole (39) at an edge corner of the bottom side parallel to the center line of the optical fiber (10).

7. The ultrastable cavity with the optical fiber as the cavity according to any one of claims 3 to 6, characterized in that: The four side surfaces and the top surface of the cavity fixing frame (17) are provided with mounting holes (40); the heat-insulating component (9) includes a heating plate (41) and a heat-insulating layer (42); each side surface of the fixing seat (16) is provided with a heating plate (41); and each mounting hole (40) is embedded with the heat-insulating layer (42).

8. The ultrastable cavity with the optical fiber as the cavity according to any one of claims 3 to 5, characterized in that: The fixing seat (16) is fixed in the accommodating cavity (18) of the cavity fixing frame (17), and a gap is provided between the fixing seat (16) and the cavity fixing frame (17).

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