Ultra-stable cavity with optical fiber as cavity body

Abstract

The invention belongs to the technical field of laser frequency stabilization, and discloses an ultra-stable cavity with an optical fiber as a cavity, which comprises an optical fiber cavity component, the optical fiber cavity component comprises an optical fiber, the two ends of the optical fiber are plated with high-reflection films, and the two ends of the optical fiber in the length direction are provided with optical fiber connecting pieces. The ultra-stable cavity provided by the invention adopts the optical fiber, uses the optical fiber optical path, does not depend on vacuum, effectively reduces the volume of the ultra-stable cavity, can get rid of the dependence of a PDH frequency stabilization system on the polarization characteristic of the optical path, does not need to carry out complex cavity-mode coupling, avoids tedious mode matching and optical path adjustment, and is simple and convenient to operate.

Description

Technical Field

[0001] The 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 one of the best performing methods in current laser frequency stabilization systems.

[0003] Ultrastable cavities are mainly used in PDH frequency stabilization systems. Light that needs to be frequency stabilized is injected into the ultrastable cavity. The reflected light intensity of the cavity is monitored while scanning the laser frequency. The minimum value of the reflected light intensity can be seen, and then the laser frequency can be stabilized at the point where the reflected light intensity is the minimum through the PDH frequency stabilization system. In order to ensure the mode stability of the ultrastable cavity, the ultrastable cavity is usually insulated and vacuum treated.

[0004] The existing ultra-stable cavity uses a highly sealed vacuum cavity to maintain its internal vacuum, which is relatively large in size. Since the propagation of spatial light is basically not restricted by any restrictions, its transverse mode can be any transverse mode, and there is only one transverse mode that can fully match the ultra-stable cavity. In order to match the transverse mode of the spatial light with the transverse mode of the ultra-stable cavity, a specially designed optical path is required to shape the spatial light. When performing cavity mode matching, since only light whose transverse mode and longitudinal mode simultaneously match the ultra-stable cavity mode can pass through the ultra-stable cavity, it is not particularly intuitive to see the phenomenon of successful mode matching, which also increases the difficulty of optical path adjustment to a certain extent.

[0005] like Figure 1 As shown, the existing ultra-stable cavity optical path is all spatial light path. If you want to ensure that the incident light can be coupled into the ultra-stable cavity, you need 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 ensure 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, and to ensure that the base film transmittance reaches the highest.

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

[0007] In view of the above problems, the present invention provides an ultra-stable cavity with optical fiber as the cavity, adopting the following technical solutions:

[0008] An ultra-stable 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 preservation component is arranged on the mounting and fixing component;

[0011] The optical fiber cavity component further includes a protective layer, and the protective layer is coated on the outer side 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] Among them, 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 thermal 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] Further, the optical fiber connector includes an optical fiber flange and an adapter;

[0016] Among them, the optical fiber flange includes a flange plate, a stud and an elastic sleeve, and the flange plate is provided with bosses on both sides parallel to the fixing seat, and the flange plate and the bosses on the two sides are provided with penetrating internal threaded holes, the external thread on the outer side of the stud is threadedly connected with the internal threaded hole, the stud is provided with a second through hole along the axial direction, 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] Further, the fixing seat includes an upper fixing block and a lower fixing block;

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

[0019] Further, the adapter comprises a connecting plate, a concave platform is arranged at the center of the outer side surface of the connecting plate, a positioning hole is arranged 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 inside 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 fixed block and the lower fixed block are both provided with threaded blind holes on two side surfaces perpendicular to the center line of the optical fiber, and the connecting plate is provided with a plurality of fourth through holes, the fourth through holes on the upper part of the connecting plate correspond to the positions of the threaded blind holes on the upper fixed 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 fixed 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 arranged on the four sides and the top surface of the cavity fixing frame, the heat-insulating component comprises a heating plate and a heat-insulating layer, a heating plate is arranged on each side of the fixing seat, and the heat-insulating 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 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 cumbersome 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 partly become obvious from the description, or be understood by implementing 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 briefly introduces 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 creative work.

[0029] Figure 1 A schematic diagram of the optical path structure of an ultra-stable 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 an 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 an installation and fixing component 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 A schematic structural diagram of a fixing base according to an embodiment of the present invention is shown;

[0036] Figure 8 A schematic structural diagram of a transition piece according to an embodiment of the present invention is shown;

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

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

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

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

[0041] In the 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, insulation component; 10, optical fiber; 11, optical fiber connector; 12, protective layer; 13, first through hole; 14, high reflection 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, recess; 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, optical fiber circulator. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

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

[0044] The present invention provides an ultra-stable cavity using an optical fiber as a cavity, which is independent of vacuum, reduces the volume of the device, avoids cumbersome 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 a cavity comprises 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, and 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 optical fiber connectors (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 for heating and heat preservation of the optical fiber 10; the optical signal input end is connected to the optical fiber 10 through the optical fiber connector 11, and it can be used as an ultra-stable cavity.

[0048] like Figure 3 As shown, for example, the optical fiber cavity component 7 also 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] In the formula, 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, 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, both ends of the optical fiber 10 in the length direction are located outside the protective layer 12, and high-reflection films 14 are applied on both end surfaces 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 material, 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, and then pass the two 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 end faces of the optical fiber 10 and the connecting column 15 smooth, embed the connecting column 15 into the protective layer 12 and firmly bond it, 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, and a fiber Bragg grating Fabry-Perot cavity is obtained by irradiating the two ends of the optical fiber 10 with ultraviolet light. 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, and this 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 a 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 coated on the outside of the protective layer 12, the heat preservation component 9 is coated 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 optical fiber flange 19 includes a flange plate 21, a stud 22 and an elastic sleeve 23. The central positions of the two side surfaces of the square flange plate 21 parallel to the fixing seat 16 are provided with bosses 24. The flange plate 21 and the bosses 24 on the two side surfaces are provided with internal threaded holes. The outer side of the stud 22 is provided with external threads matching the internal threaded holes. The external threads of the stud 22 are threadedly connected with the internal threaded holes. The stud 22 is provided with a second through hole 25 along the axial direction. The elastic sleeve 23 is provided in the second through hole 25. The elastic sleeve 23 is sleeved on the connecting column 15. The inner diameter of the elastic sleeve 23 matches the outer diameter of the connecting column 15. The optical fiber 10 wrapped by the connecting column 15 can be aligned through the elastic sleeve 23.

[0059] The flange plate 21 is detachably connected to the adapter 20, and the adapter 20 is detachably connected to the fixing seat 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, 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, and 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, and the specification of the threaded blind holes 31 is M4. 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 the inside of the recess 33 is provided with four third through holes 36 corresponding to the positions of the first countersunk holes 35 along the circumference of the positioning hole 34. Bolts pass through the third through holes 36 and are connected to nuts, so that the flange plate 21 and the connecting plate 32 are detachably connected.

[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 of the upper fixing block 27; the angle between the center line of the first blind hole 38 and the vertical side of the upper fixing block 27 is 45°; the bottom side 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 of the lower fixing block 28 is 45°, so as to ensure the uniformity of temperature control.

[0067] like Fig. 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. Fig.10 As shown, each side of the fixing seat 16 is provided with a heating plate 41, and 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 an 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 sheet 41 uses a flexible printed circuit board (FPC). In the prior art, whether an air conditioner or a semiconductor refrigerator (TEC) is used for heat preservation, the vibration of the fan will inevitably be introduced. Therefore, a flexible printed circuit board (FPC) is selected for heating so that the cavity can be temperature-stabilized at a temperature higher than room temperature. The heating sheet 41 is fixed to the surface of the fixing seat 16 by adhesive and covers as large an area as possible.

[0069] For example, the thermal insulation layer 42 selects EVA foam material with more cavities as the thermal insulation material, which can be embedded in the cavity fixing frame 17 to completely block the internal cavity from contact with the outside 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 there is a gap between the fixing seat 16 and the cavity fixing frame 17, so as to reduce the contact between the fixing seat 16 and the cavity fixing frame 17 and reduce unnecessary heat transfer. For example, the first threaded holes 43 are arranged on the four edges of the cavity fixing frame 17 parallel to the center line of the optical fiber 10, for example, three first threaded holes 43 are arranged 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 fixed to the center of the accommodating cavity 18 of the cavity fixing frame 17 by bolts being threadedly connected to the first threaded holes 43, and a plurality of bolts abut against the four edges of the fixing seat 16, so as to have a gap between the fixing seat 16 and the cavity fixing frame 17, so as to reduce the contact between the fixing seat 16 and the cavity fixing frame 17 as much as possible.

[0072] like Fig. 9 As shown, for example, a square base 44 is also 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 hole 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 damping plate 46, and the bottom of the base 44 is detachably connected to the damping plate 46. The ultra-stable cavity adopts a passive damping method to isolate it from the outside world and achieve a damping effect.

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

[0075] like Fig.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 bolts passing through the second countersunk hole 45 and threadedly connected to the second threaded hole 47.

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

[0077] like Fig.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 as long as light is passed through. The optical fiber 10 is a solid structure, which can eliminate the dependence of the ultra-stable cavity on vacuum. Leaving 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 substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultrastable cavity with optical fiber as cavity, characterized in that: The optical fiber cavity component (7) comprises an optical fiber (10), both ends of the optical fiber (10) are coated with high-reflection films (14), and both ends of the optical fiber (10) in the length direction are provided with optical fiber connectors (11).

2. The ultrastable cavity using 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 using the optical fiber as the cavity according to claim 2, characterized in that: Both ends of the optical fiber (10) in the length 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).

4. The ultrastable cavity using the optical fiber as the cavity according to claim 3, characterized in that: The installation and fixing component (8) comprises a fixing seat (16) and a cavity fixing frame (17); The cavity fixing frame (17) has a 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 coated on the outside of the protective layer (12), the heat preservation component (9) is coated on the outside of the cavity fixing frame (17), and the connecting column (15) is detachably connected to the fixing seat (16) via an optical fiber connector (11).

5. The ultrastable cavity using the optical fiber as the cavity according to claim 4, characterized in that: The optical fiber connector (11) comprises an optical fiber flange (19) and an adapter (20); The optical fiber flange (19) comprises a flange plate (21), a stud (22) and an elastic sleeve (23); the flange plate (21) and two side surfaces parallel to the fixing seat (16) are provided with bosses (24); the flange plate (21) and the bosses (24) on the two side surfaces are provided with penetrating internal threaded holes; the external thread on the outer side of the stud (22) is threadedly connected with the internal threaded hole; the stud (22) is provided with a second through hole (25) along the axial direction; the elastic sleeve (23) is arranged in the second through hole (25); 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 fixing seat (16).

6. The ultrastable cavity using the optical fiber as the cavity according to claim 5, characterized in that: The fixing seat (16) comprises 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) and the lower fixing block (28) are detachably connected to the adapter (20).

7. The ultrastable cavity using the optical fiber as the cavity according to claim 6, characterized in that: The adapter (20) comprises a connecting plate (32), a concave platform (33) is arranged at the center of the outer side surface of the connecting plate (32), a positioning hole (34) is arranged at the center of the concave platform (33), the flange plate (21) is located in the concave platform (33), and the convex platform (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 the inside of the recessed platform (33) is provided with a third through hole (36) corresponding to the position of the first countersunk hole (35) 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 in position to 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 in position to the threaded blind holes (31) on the lower fixing block (28).

8. The ultrastable cavity using the optical fiber as the cavity according to claim 6, 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).

9. An ultrastable cavity with an optical fiber as a cavity according to any one of claims 3 to 7, 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) comprises 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).

10. An ultrastable cavity with an optical fiber as a cavity according to any one of claims 4 to 7, 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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