Fabry-Perot cavity with length compensation

Abstract

The invention discloses a Fabry-Perot cavity with length compensation. The Fabry-Perot cavity comprises a first cavity mirror, a second cavity mirror, a first compensation piece, a first fixing piece and a cavity body. And the thermal expansion coefficient of a manufacturing material of the cavity is different from that of a manufacturing material of the first compensation piece. The first fixing piece is fixed on the outer side of the first end of the cavity; a hollow area penetrating through the cavity is arranged in the center of the first fixing part in the optical axis direction of the cavity, and fine threads are arranged on the edge of the inner side of the hollow area. The second end of the first compensation piece penetrates through the hollow area of the first fixing piece and extends into the cavity, and the side face of the first compensation piece is connected with the first fixing piece through fine threads. The first cavity mirror is fixed at the second end of the first compensation piece; and the second endoscope is fixed at the second end of the cavity. According to the FP cavity provided by the invention, the influence of the thermal expansion and cold contraction effect of the cavity body and the cavity mirror material caused by the environment temperature change on the cavity length is remarkably reduced, and the FP cavity can stably work under different temperature conditions.

Description

Technical Field

[0001] The present application relates to the field of optical technology, and in particular to a length-compensated Fabry-Perot cavity. Background Art

[0002] The Fabry-Perot cavity (FP cavity) is a key optical resonant cavity structure, which is widely used in fields such as ultra-precision laser spectroscopy and quantum precision measurement. The FP cavity consists of two parallel high-reflectivity mirrors and a transparent medium (such as air, glass, etc.) in the middle. After the light enters the FP cavity, it is reflected and superimposed multiple times between the mirrors, forming an interference effect; when the wavelength of light meets specific resonance conditions, a stable resonant mode will be formed in the FP cavity, with efficient transmission and discrete transmission peaks at the output end.

[0003] The thermal expansion and contraction effect of the cavity and mirror materials caused by changes in ambient temperature will cause the cavity length of the FP cavity to change, thereby affecting the stability of the FP cavity. How to design a FP cavity that can work stably under different temperature conditions has become one of the technical problems that need to be solved in the field of optical technology. Summary of the invention

[0004] Based on the above problems, the present application provides a length-compensated Fabry-Perot cavity, which significantly reduces the impact of the thermal expansion and contraction effects of the cavity and cavity mirror materials caused by ambient temperature changes on the stability of the FP cavity. It is a FP cavity that can operate stably under different temperature conditions.

[0005] The present application discloses a length-compensated Fabry-Perot cavity, comprising: A first cavity mirror, a second cavity mirror, a first compensating member, a first fixing member and a cavity; the thermal expansion coefficient of a material making the cavity is different from the thermal expansion coefficient of a material making the first compensating member; The first fixing member is fixed to the outside of the first end of the cavity; a hollow area penetrating the first fixing member is provided at the center of the first fixing member along the optical axis direction of the cavity, and a fine thread is provided at the inner edge of the hollow area of ​​the first fixing member; The first end of the first compensating member is outside the first fixing member, the second end of the first compensating member passes through the hollow area of ​​the first fixing member and extends into the interior of the cavity, and the first compensating member is connected to the first fixing member through a fine thread on the inner edge of the hollow area of ​​the first fixing member; The first cavity mirror is fixed to the second end of the first compensation member; the second cavity mirror is fixed to the second end of the cavity.

[0006] In an optional implementation, the length of the cavity is L0, the distance between the second end of the first compensation member and the first end of the cavity is L1, the thermal expansion coefficient of the material of the cavity is α0, and the thermal expansion coefficient of the material of the first compensation member is α1; The L0, the L1, the α0 and the α1 satisfy a first constraint formula; the first constraint formula is: α0×L0=2×α1×L1.

[0007] In an optional implementation, the second laparoscope is fixed to the second end of the cavity, specifically: the second laparoscope is bonded to the second end of the cavity.

[0008] In an optional implementation, the first fixing member is fixed to the outer side of the first end of the cavity, specifically: the side surface of the first fixing member perpendicular to the optical axis of the cavity is bonded to the outer side of the first end of the cavity; The first cavity mirror is fixed to the second end of the first compensation member, specifically: the second end of the first compensation member is bonded to the bottom of the first cavity mirror.

[0009] In an optional implementation, the thermal expansion coefficient of the material of which the cavity is made is smaller than the thermal expansion coefficient of the material of which the first compensation piece is made.

[0010] In an optional implementation, the cavity is made of a material including: fused quartz, ULE or ceramic.

[0011] In an optional implementation, the Fabry-Perot cavity further includes: a second compensating member and a second fixing member; the thermal expansion coefficient of the material of the second compensating member is different from the thermal expansion coefficient of the material of the cavity; The second cavity mirror is fixed to the second end of the cavity, specifically: The second fixing member is fixed to the outside of the second end of the cavity; a hollow area penetrating the second fixing member is provided at the center of the second fixing member along the optical axis direction of the cavity, and a fine thread is provided at the inner edge of the hollow area of ​​the second fixing member; The first end of the second compensating member passes through the hollow area of ​​the second fixing member and extends into the interior of the cavity, and the second compensating member is connected to the second fixing member through a fine thread on the inner edge of the hollow area of ​​the second fixing member; the second end of the second compensating member is located outside the second fixing member; The second cavity mirror is fixed to the first end of the second compensation member.

[0012] In an optional implementation, the length of the cavity is L0, the distance between the second end of the first compensation member and the first end of the cavity is L1, the thermal expansion coefficient of the material of the cavity is α0, and the thermal expansion coefficient of the material of the first compensation member is α1; the distance between the first end of the second compensation member and the second end of the cavity is L2, and the thermal expansion coefficient of the material of the second compensation member is α2; The L0, the L1, the L2, the α0, the α1 and the α2 satisfy a second constraint formula; the second constraint formula is: α0×L0=2×α1×L1+2×α2×L2.

[0013] In an optional implementation, the second fixing member is fixed to the outer side of the second end of the cavity, specifically: the side surface of the second fixing member perpendicular to the optical axis of the cavity is bonded to the outer side of the second end of the cavity; The second cavity mirror is fixed to the first end of the second compensation member, specifically: the first end of the second compensation member is bonded to the bottom of the second cavity mirror.

[0014] In an optional implementation, the thermal expansion coefficient of the material of which the cavity is made is smaller than the thermal expansion coefficient of the material of which the first compensation piece is made, and smaller than the thermal expansion coefficient of the material of which the second compensation piece is made.

[0015] Compared with the prior art, this application has the following beneficial effects: In the Fabry-Perot cavity disclosed in the present application, the first cavity mirror is fixedly connected to the second end of the first compensating member, and the first compensating member is connected to the first fixing member through a fine thread. When the change in ambient temperature causes the thermal expansion and contraction effect of the cavity body and the cavity mirror material, resulting in a change in the cavity length of the FP cavity, the distance between the first cavity mirror and the second cavity mirror can be changed by adjusting the length of the second end of the first compensating member penetrating into the cavity, thereby changing the cavity length of the FP cavity, compensating for the effect of the ambient temperature change on the cavity length change, and improving the stability of the FP cavity; further, since the cavity material and the first compensating member used in the present application have different thermal expansion coefficients, the adjustment range of the equivalent zero expansion temperature point of the FP cavity is expanded, which is also conducive to improving the stability and accuracy of the FP cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0017] Figure 1 A cross-sectional view of a length-compensated Fabry-Perot cavity provided in an embodiment of the present application; Figure 2 A side view of a first fixing member provided in an embodiment of the present application; Figure 3 A cross-sectional view of another length-compensated Fabry-Perot cavity provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] The FP cavity is a key optical resonant cavity structure, which is widely used in fields such as ultra-precision laser spectroscopy and quantum precision measurement. The FP cavity consists of two parallel high-reflectivity mirrors and a transparent medium (such as air, glass, etc.) in the middle. After the light enters the FP cavity, it is reflected and superimposed multiple times between the mirrors, forming an interference effect; when the wavelength of light meets specific resonance conditions, a stable resonance mode will be formed in the FP cavity, with efficient transmission and discrete transmission peaks at the output end.

[0019] At present, a problem faced by the FP cavity during use is that the thermal expansion and contraction effect of the cavity and cavity mirror materials caused by changes in ambient temperature will cause the cavity length of the FP cavity to change, thereby affecting the stability of the FP cavity. Therefore, how to design a FP cavity that can work stably under different temperature conditions has become one of the technical problems that need to be solved in the field of optical technology.

[0020] Based on the above problems, the present application discloses a length-compensated Fabry-Perot cavity, comprising: a first cavity mirror, a second cavity mirror, a first compensating member, a first fixing member and a cavity. The thermal expansion coefficient of the material of the cavity is different from the thermal expansion coefficient of the material of the first compensating member. The first fixing member is fixed to the outside of the first end of the cavity; the center position of the first fixing member is provided with a hollow area passing through it along the optical axis direction of the cavity, and the inner edge of the hollow area is provided with a fine thread; the second end of the first compensating member extends into the interior of the cavity through the hollow area of ​​the first fixing member, and the side of the first compensating member is connected to the first fixing member by a fine thread; the first cavity mirror is fixed to the second end of the first compensating member; the second cavity mirror is fixed to the second end of the cavity.

[0021] Since the first cavity mirror and the first compensating member in the Fabry-Perot cavity disclosed in the present application are fixedly connected, and the first compensating member is connected to the first fixing member through a fine thread. When the change in ambient temperature causes the thermal expansion and contraction effect of the cavity body and cavity mirror materials, resulting in a change in the cavity length of the FP cavity, the cavity length of the FP cavity can be changed by adjusting the length of the second end of the first compensating member penetrating into the cavity, changing the distance between the first cavity mirror and the second cavity mirror, thereby compensating for the effect of the change in ambient temperature on the change in cavity length and improving the stability of the FP cavity; further, since the cavity material and the first compensating member used in the present application have different thermal expansion coefficients, the adjustment range of the equivalent zero expansion temperature point of the FP cavity is expanded, which is also conducive to improving the stability and accuracy of the FP cavity.

[0022] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0023] Figure 1 A cross-sectional view of a length-compensated Fabry-Perot cavity provided in an embodiment of the present application. Figure 1 As shown, the Fabry-Perot cavity disclosed in the present application has a first compensating member, a first fixing member, a first cavity mirror, a cavity and a second cavity mirror placed in sequence along the optical axis direction of the cavity of the FP cavity.

[0024] To facilitate understanding of the technical solution in this application, Figure 1 Taking the Fabry-Perot cavity shown in as an example, the definitions of the two ends of each device involved in the present application are explained.

[0025] Figure 1 The optical axis direction of the cavity is given in . For any device in the FP cavity, the end in the negative direction of the optical axis of the cavity is defined as the first end of the optical device; the end in the positive direction of the optical axis of the cavity is defined as the second end of the optical device.

[0026] For example, for the cavity, the end close to the first compensation piece is the first end of the cavity, and the end close to the second cavity mirror is the second end of the cavity.

[0027] Figure 1The specific structure of the Fabry-Perot cavity described in the invention is as follows: a first fixing member is fixed to the outside of the first end of the cavity; a hollow area penetrating the first fixing member is provided at the center position of the first fixing member along the optical axis direction of the cavity, and a fine thread is provided on the inner edge of the hollow area of ​​the first fixing member; a first end of the first compensating member is outside the first fixing member, a second end of the first compensating member passes through the hollow area of ​​the first fixing member and extends into the interior of the cavity, and the first compensating member is connected to the first fixing member through the fine thread on the inner edge of the hollow area of ​​the first fixing member; a first laparoscope is fixed to the second end of the first compensating member; a second laparoscope is fixed to the second end of the cavity; and the first laparoscope and the second laparoscope are placed in parallel.

[0028] It should be emphasized that Figure 1 The FP cavity in the cavity is symmetrical up and down along the optical axis of the cavity. Figure 1 It is a cross-sectional view of the FP cavity, in which the black solid long strip placed along the optical axis of the cavity is the first compensation piece; the white solid long strip perpendicular to the optical axis of the cavity is the first fixing piece; the gray solid long strip placed along the optical axis of the cavity is the cavity; the long strips with oblique stripes perpendicular to the optical axis of the cavity are the first cavity mirror and the second cavity mirror respectively.

[0029] Figure 2 A side view of a first fixing member provided in an embodiment of the present application. Figure 2 As shown, it can be seen more clearly that a hollow area penetrating the first fixing member is provided at the center of the first fixing member, and a fine thread is provided at the inner edge of the hollow area of ​​the first fixing member.

[0030] In an optional implementation, the first cavity mirror is fixed to the second end of the first compensation member, which means that the second end of the first compensation member is bonded to the bottom of the first cavity mirror.

[0031] In an optional implementation, the first fixing member is fixed to the outer side of the first end of the cavity, which means that a side surface of the first fixing member perpendicular to the optical axis of the cavity is bonded to the outer side of the first end of the cavity.

[0032] In an optional implementation, the second cavity mirror is fixed at the second end of the cavity, which means that the second cavity mirror is bonded to the second end of the cavity.

[0033] The advantage of using "bonding" in the present application, rather than "mechanical clamping" or "embedded fixing" to fix the first cavity mirror to the second end of the first compensation member, the first fixing member to the outside of the first end of the cavity, and the second cavity mirror to the second end of the cavity, is that the number of components can be reduced and the processing difficulty can be reduced, thereby making the structure of the FP simpler, easier to process and assemble, and lower in cost.

[0034] The thermal expansion coefficient of the material of the cavity is different from the thermal expansion coefficient of the material of the first compensation member. The cavity can be made of any one of fused quartz, ULE (Ultra-Low Expansion, ultra-low expansion coefficient glass) or ceramic.

[0035] The thermal expansion coefficient of the material for making the cavity selected in the present application is smaller than the thermal expansion coefficient of the material for making the first compensation member. For example, in the present application, fused quartz among the materials with low thermal expansion coefficient is selected as the material for making the cavity.

[0036] For example, Figure 1 The parameters of each device in the FP cavity can be: the cavity length of the FP cavity is 10 cm; the first cavity mirror and the second cavity mirror have the same size (both have a diameter of 0.5 inches); the first fixing member and the first compensating member are both made of copper-tungsten alloy; the length of the first fixing member is 10 mm; the length of the first compensating member is 20 mm.

[0037] Combination Figure 1 As shown, the length of the cavity is defined in this application as L0, the distance between the second end of the first compensation part and the first end of the cavity is L1, the thermal expansion coefficient of the material making the cavity is α0, and the thermal expansion coefficient of the material making the first compensation part is α1; L0, L1, α0 and α1 satisfy the first constraint formula; the first constraint formula is: α0×L0=2×α1×L1.

[0038] Among them, the derivation process of the first constraint formula is: The relationship between the change in cavity length ΔL of the Fabry-Perot cavity and the change in temperature ΔT of the operating environment of the Fabry-Perot cavity can be expressed by formula (1).

[0039] Formula (1) is specifically: △L=0.5×△T×α0×L0-△T×α1×L1+cavity mirror expansion (1) Since the thickness of the two cavity mirrors in the Fabry-Perot cavity is very small and the thermal expansion coefficient of the cavity mirrors is low, the expansion of the cavity mirrors can be ignored. In this way, formula (1) is simplified to formula (2).

[0040] Formula (2) is specifically: △L=0.5×△T×α0×L0-△T×α1×L1 (2) If the change △L of the cavity length of the Fabry-Perot cavity is to be zero when the ambient temperature changes, the first constraint formula is obtained, that is, α0×L0=2×α1×L1.

[0041] In summary, FIG1 discloses a length-compensated FP cavity of an asymmetric material structure. In the FP cavity, the first compensating member and the first fixing member are connected by fine-pitch threads, the second end of the first compensating member extends into the cavity of the FP cavity, and the end is bonded to the bottom of the first cavity mirror. During use, the actual temperature of the use environment of the FP cavity can be determined first; then the thermal expansion coefficient α0 of the material making the FP cavity body and the thermal expansion coefficient α1 of the material making the first compensating member can be determined at this actual temperature; after obtaining the thermal expansion coefficients of the two devices and the cavity length L0 of the FP cavity, the specific value of the distance L1 between the second end of the first compensating member and the first end of the cavity is calculated according to the first constraint formula; finally, the fine-pitch threads between the first fixing member and the first compensating member are rotated (screwed in or out) to adjust so that the distance of the second end of the first compensating member extending into the cavity is the calculated value of L1. In this way, when the temperature of the environment in which the FP cavity is located changes, the cavity temperature changes accordingly, and the first compensation component will drive the position of the first cavity mirror to change, thereby changing the distance between the first cavity mirror and the second cavity mirror, and then changing the cavity length of the FP cavity, and finally adjusting the equivalent zero expansion temperature point of the FP cavity to near the target temperature.

[0042] Figure 3 A cross-sectional view of another length-compensated Fabry-Perot cavity provided in an embodiment of the present application. Figure 3 As shown, the Fabry-Perot cavity disclosed in the present application has a first compensating member, a first fixing member, a first cavity mirror, a cavity, a second cavity mirror, a second fixing member and a second compensating member placed in sequence along the optical axis direction of the cavity of the FP cavity.

[0043] It should be noted that Figure 3 The definition of the first end and the second end of each device in the FP cavity; as well as the device names represented by different long strips, refer to the above Figure 1 The introduction of relevant contents will not be repeated here.

[0044] Figure 3The specific structure of the Fabry-Perot cavity is as follows: a first fixing member is fixed on the outside of the first end of the cavity; a hollow area penetrating the first fixing member is provided at the center position of the first fixing member along the optical axis direction of the cavity, and a fine thread is provided on the inner edge of the hollow area of ​​the first fixing member; a first end of the first compensating member is on the outside of the first fixing member, a second end of the first compensating member passes through the hollow area of ​​the first fixing member and extends into the interior of the cavity, and the first compensating member is connected to the first fixing member through the fine thread on the inner edge of the hollow area of ​​the first fixing member; and a first cavity mirror is fixed on the second end of the first compensating member. The second fixing piece is fixed on the outer side of the second end of the cavity; a hollow area penetrating the second fixing piece is provided at the center position of the second fixing piece along the optical axis direction of the cavity, and a fine thread is provided on the inner edge of the hollow area of ​​the second fixing piece; the first end of the second compensating piece passes through the hollow area of ​​the second fixing piece and extends into the interior of the cavity, and the second compensating piece is connected to the second fixing piece through the fine thread on the inner edge of the hollow area of ​​the second fixing piece; the second end of the second compensating piece is located on the outer side of the second fixing piece; the second laparoscope is fixed on the first end of the second compensating piece; the first laparoscope and the second laparoscope are placed in parallel.

[0045] It should be noted that Figure 3 The detailed structure of the first fixing member and the second fixing member can be found in Figure 2 The relevant introduction in will not be repeated here.

[0046] It should be noted that Figure 3 The first laparoscope being fixed at the second end of the first compensation piece means that the second end of the first compensation piece is bonded to the bottom of the first laparoscope; the second laparoscope being fixed at the first end of the second compensation piece means that the first end of the second compensation piece is bonded to the bottom of the first laparoscope.

[0047] Figure 3 The first fixing member being fixed to the outer side of the first end of the cavity means that the side of the first fixing member perpendicular to the optical axis of the cavity is bonded to the outer side of the first end of the cavity; the second fixing member being fixed to the side of the second end of the cavity means that the side of the second fixing member perpendicular to the optical axis of the cavity is bonded to the outer side of the second end of the cavity.

[0048] It should be noted that Figure 3 The thermal expansion coefficient of the material of the cavity is smaller than the thermal expansion coefficient of the material of the first compensation member, and smaller than the thermal expansion coefficient of the material of the second compensation member. Exemplarily, the material of the cavity includes: fused quartz, ULE or ceramic.

[0049] like Figure 3As shown, the length of the FP cavity is L0, the distance between the second end of the first compensation part and the first end of the cavity is L1, the thermal expansion coefficient of the material making the cavity is α0, and the thermal expansion coefficient of the material making the first compensation part is α1; the distance between the first end of the second compensation part and the second end of the cavity is L2, and the thermal expansion coefficient of the material making the second compensation part is α2.

[0050] Among them, L0, L1, L2, α0, α1 and α2 satisfy the second constraint formula. The second constraint formula is: α0×L0=2×α1×L1+2×α2×L2.

[0051] It should be noted that in addition to the thermal expansion coefficients of the material making the first compensation part being α1 and the thermal expansion coefficients of the material making the second compensation part being α2, the distance between the second end of the first compensation part and the first end of the cavity being L1 and the distance between the first end of the second compensation part and the second end of the cavity being L2 may also be different.

[0052] The derivation process of the second constraint formula is as follows: The relationship between the change in cavity length ΔL of the Fabry-Perot cavity and the change in temperature ΔT of the operating environment of the Fabry-Perot cavity can be expressed by formula (3).

[0053] Formula (3) is specifically: △L=0.5×△T×α0×L0-△T×α1×L1+cavity mirror expansion-△T×α2×L2 (3) Since the thickness of the two cavity mirrors in the Fabry-Perot cavity is very small and the thermal expansion coefficient of the cavity mirrors is low, the expansion of the cavity mirrors can be ignored. In this way, formula (3) is simplified to formula (4).

[0054] Formula (4) is specifically: △L=0.5×△T×α0×L0-△T×α1×L1-△T×α2×L2 (4) If the change △L of the cavity length of the Fabry-Perot cavity is to be zero when the ambient temperature changes, the second constraint formula is obtained, namely α0×L0=2×α1×L1+2×α2×L2.

[0055] In summary, a length-compensated FP cavity of an asymmetric material structure is disclosed in Fig. 3. In the FP cavity, the first compensating member and the first fixing member are connected by fine-pitch threads, the second end of the first compensating member extends into the FP cavity, and the end is bonded to the bottom of the first cavity mirror; the second compensating member and the second fixing member are connected by fine-pitch threads, the first end of the second compensating member extends into the FP cavity, and the end is bonded to the bottom of the second cavity mirror. During use, the actual temperature of the use environment of the FP cavity can be determined first; then the thermal expansion coefficient α0 of the material of the FP cavity, the thermal expansion coefficient α1 of the material of the first compensation member, and the thermal expansion coefficient α2 of the material of the second compensation member under this actual temperature are determined; after obtaining these three thermal expansion coefficients and the cavity length L0 of the FP cavity, the values ​​of the distance L1 between the second end of the first compensation member and the first end of the cavity and the distance L2 between the first end of the second compensation member and the second end of the cavity are calculated according to the second constraint formula; finally, by rotating the fine thread between the first fixing member and the first compensation member, and the fine thread between the second fixing member and the second compensation member, L1 and L2 are adjusted to the corresponding values ​​calculated. In this way, when the cavity temperature of the FP cavity changes with the ambient temperature, the first compensation member will drive the position of the first cavity mirror to change, and the second compensation member will drive the position of the second cavity mirror to change, thereby changing the distance between the first cavity mirror and the second cavity mirror, and then changing the cavity length of the FP cavity, and finally adjusting the equivalent zero expansion temperature point of the FP cavity to near the target temperature.

[0056] It is understandable that the above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A length-compensated Fabry-Perot cavity, characterized in that: include: A first cavity mirror, a second cavity mirror, a first compensating member, a first fixing member and a cavity; the thermal expansion coefficient of a material making the cavity is different from the thermal expansion coefficient of a material making the first compensating member; The first fixing member is fixed to the outside of the first end of the cavity; a hollow area penetrating the first fixing member is provided at the center of the first fixing member along the optical axis direction of the cavity, and a fine thread is provided at the inner edge of the hollow area of ​​the first fixing member; The first end of the first compensating member is outside the first fixing member, the second end of the first compensating member passes through the hollow area of ​​the first fixing member and extends into the interior of the cavity, and the first compensating member is connected to the first fixing member through a fine thread on the inner edge of the hollow area of ​​the first fixing member; The first cavity mirror is fixed to the second end of the first compensation member; the second cavity mirror is fixed to the second end of the cavity.

2. The Fabry-Perot cavity according to claim 1, characterized in that: The length of the cavity is L0, the distance between the second end of the first compensating member and the first end of the cavity is L1, the thermal expansion coefficient of the material of the cavity is α0, and the thermal expansion coefficient of the material of the first compensating member is α1; The L0, the L1, the α0 and the α1 satisfy a first constraint formula; The first constraint formula is: α0×L0=2×α1×L1.

3. The Fabry-Perot cavity according to claim 1, characterized in that: The second cavity mirror is fixed to the second end of the cavity, specifically: The second cavity mirror is bonded to the second end of the cavity.

4. The Fabry-Perot cavity according to claim 1, characterized in that: include: The first fixing member is fixed to the outside of the first end of the cavity, specifically: The side surface of the first fixing member perpendicular to the optical axis of the cavity is bonded to the outer side of the first end of the cavity; The first cavity mirror is fixed to the second end of the first compensation member, specifically: The second end of the first compensation member is bonded to the bottom of the first cavity mirror.

5. The Fabry-Perot cavity according to any one of claims 1 to 4, characterized in that: The thermal expansion coefficient of the material of which the cavity is made is smaller than the thermal expansion coefficient of the material of which the first compensation piece is made.

6. The Fabry-Perot cavity according to any one of claims 1 to 4, characterized in that: The cavity is made of materials including fused quartz, ULE or ceramics.

7. The Fabry-Perot cavity according to claim 1, characterized in that: Also includes: a second compensating member and a second fixing member; the thermal expansion coefficient of the material of the second compensating member is different from the thermal expansion coefficient of the material of the cavity; The second cavity mirror is fixed to the second end of the cavity, specifically: The second fixing member is fixed to the outside of the second end of the cavity; a hollow area penetrating the second fixing member is provided at the center of the second fixing member along the optical axis direction of the cavity, and a fine thread is provided at the inner edge of the hollow area of ​​the second fixing member; The first end of the second compensating member passes through the hollow area of ​​the second fixing member and extends into the interior of the cavity, and the second compensating member is connected to the second fixing member through a fine thread on the inner edge of the hollow area of ​​the second fixing member; the second end of the second compensating member is located outside the second fixing member; The second cavity mirror is fixed to the first end of the second compensation member.

8. The Fabry-Perot cavity according to claim 7, characterized in that: The length of the cavity is L0, the distance between the second end of the first compensating member and the first end of the cavity is L1, the thermal expansion coefficient of the material of the cavity is α0, and the thermal expansion coefficient of the material of the first compensating member is α1; the distance between the first end of the second compensating member and the second end of the cavity is L2, and the thermal expansion coefficient of the material of the second compensating member is α2; The L0, the L1, the L2, the α0, the α1 and the α2 satisfy a second constraint formula; The second constraint formula is: α0×L0=2×α1×L1+2×α2×L2.

9. The Fabry-Perot cavity according to claim 7, characterized in that: include: The second fixing member is fixed to the outside of the second end of the cavity, specifically: The side surface of the second fixing member perpendicular to the optical axis of the cavity is bonded to the outer side of the second end of the cavity; The second cavity mirror is fixed to the first end of the second compensation member, specifically: The first end of the second compensation member is bonded to the bottom of the second cavity mirror.

10. The Fabry-Perot cavity according to any one of claims 7 to 9, characterized in that: The thermal expansion coefficient of the material of which the cavity is made is smaller than the thermal expansion coefficient of the material of which the first compensation member is made, and is smaller than the thermal expansion coefficient of the material of which the second compensation member is made.

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