A full glass fiber collimator applied to gravitational wave detection

Abstract

The application relates to a full-glass optical fiber collimator applied to gravitational wave detection, which is sequentially provided with a pigtail protective sleeve, a titanium alloy stress relief block, a glass structural member and an aspheric lens; the titanium alloy stress relief block and the glass structural member are inserted together through a ceramic ferrule; the right end of the glass structural member is provided with a lens limiting end face; the left side face of the aspheric lens is in contact with the lens limiting end face; the center of the right side face of the aspheric lens is the coordinate origin; the ceramic ferrule is inserted into the glass structural member by adjusting the depth, and the distance between the ceramic ferrule and the left side face of the aspheric lens is adjusted, so that the focusing of the full-glass optical fiber collimator is completed. The full-glass optical fiber collimator applied to gravitational wave detection can meet multiple different working distances at the same time in an inter-satellite laser interferometric measurement system, and the effective spot diameter of a Gaussian light beam is completely smaller than the diameter of a photoelectric detector. The wavefront difference of the Gaussian light beam at each different working distance meets the interference condition of a coherent light beam, and interference phenomenon is generated.

Description

Technical Field

[0001] This invention relates to the fields of gravitational wave measurement, optical design, and interferometry, and particularly to an all-glass fiber collimator for gravitational wave detection. Background Technology

[0002] Ground-based gravitational wave detection is constrained by factors such as the Earth's radius of curvature, gravitational gradient noise, earthquakes, and tsunamis. Furthermore, the sources of gravitational waves are extremely limited. To overcome these limitations and obtain more gravitational wave sources, researchers have begun developing space-based gravitational wave detection.

[0003] When detecting gravitational waves in space, an inter-satellite laser interferometry (LIFE) optical system is required. The optical component of this system mainly consists of a gravitational wave telescope and a laser interferometer platform. The Gaussian beam generated from the laser, after exiting through the optical fiber, cannot be directly used by the all-glass laser interferometer platform. To ensure that the beam emitted from the laser's optical fiber meets the requirements of the all-glass laser interferometer, an all-glass fiber optic collimator (FIOS) needs to be designed and manufactured according to specific conditions.

[0004] The design and manufacture of fiber optic collimators that meet the requirements of practical use involve fields such as gravitational wave detection, optical communication technology, optical design, and optical assembly.

[0005] To detect gravitational waves in space, an inter-satellite laser interferometry optical system is required. To ensure that the inter-satellite laser interferometry optical system can achieve measurement accuracy at the picometer level, the optical path stability of the optical system must be strictly required.

[0006] Fiber collimators are used in all-glass laser interferometers. Since the all-glass fiber collimator is tightly bonded to the substrate of the all-glass laser interferometer and is an important component of the laser interference optical path, the stability of the fiber collimator is also highly demanded.

[0007] Because microcrystalline glass has good low expansion properties, it is used to manufacture all-glass fiber collimators (FIOS).

[0008] Typically, a Gaussian beam in an optical fiber, after passing through a collimating lens, operates only at a specific receiving end, thus requiring a collimator optical system designed for a single working distance. However, in an all-glass laser interferometer, the all-glass fiber optic collimator (FIOS) simultaneously offers 10 different working distances.

[0009] Because the all-glass laser interferometer internally includes a reference interference path, a test quality interference path, and a scientific interference path, the first FIOS (FIOSⅠ in the image) emits a beam from the last aspherical surface of the collimating lens. After a series of beam splitting and combining, the beam is incident on two photodetectors, with corresponding beam path lengths of 1100mm and 1145mm. The second FIOS (FIOSⅡ in the image) emits a beam from the last aspherical surface of the collimating lens. After a series of beam splitting and combining, the beam is incident on two photodetectors, with corresponding path lengths of 480mm and 525mm. Figure 1 As shown.

[0010] For the scientific interferometer, only the beam emitted by the first FIOS was used. This beam was split or combined in a series of steps and then incident on two photodetectors. The path lengths of the two beams on the two photodetectors were 550 mm and 520 mm, respectively. Figure 2 As shown.

[0011] For the reference interferometer optical path, the first FIOS emits a beam from the last surface of the collimating mirror. After a series of beam splitting and combining, the beam is incident on two photodetectors, with corresponding beam path lengths of 510 mm and 540 mm. For example... Figure 3 As shown, after the second FIOS emits a beam from the last surface of the collimating lens, it undergoes a series of beam splitting and combining before being incident on the two photodetectors, with corresponding path lengths of 485mm and 515mm.

[0012] Each interferometer uses a Gaussian beam emitted by a fiber optic collimator, so the all-glass fiber optic collimator (FIOS) must be able to achieve optical interference conditions at multiple different working distances.

[0013] Since the effective working area diameter of the photodetector used is 1.2 mm, the effective diameter of the Gaussian beam is required to not exceed 1.2 mm to ensure that the entire spot within the diameter of the Gaussian beam illuminates the photodetector.

[0014] The Rayleigh distance of the fiber optic collimator (FIOS) must be long enough, and the waist position must be appropriate to ensure that multiple working distances fall within the Rayleigh distance range of the FIOS. Furthermore, unlike metal structures, the FIOS requires consideration of fabrication feasibility and ease of assembly.

[0015] For the all-glass fiber optic collimator FIOS, foreign-designed finished products such as... Figure 4 , Figure 5 As shown, it is applied in the LISAPathfinder laser interferometer.

[0016] The specific assembly and adjustment method is as follows: Figure 4 , Figure 5 The working distances of the all-glass fiber optic collimator (FIOS) in the model are 765.41 mm and 406.58 mm. During the manufacturing of the FIOS, due to potential height discrepancies between the aspherical lens and the ceramic ferrule end face, it is necessary to repeatedly grind the aspherical lens glass support or square glass support block to ensure that the optical axis of the aspherical lens is at the same height as the central axis of the ceramic ferrule. Then, the distance between the collimating lens and the ceramic ferrule end face needs to be adjusted to control the distribution of the system beam energy. Furthermore, the pitch and yaw angles of the aspherical lens must be adjusted to ensure that the FIOS meets the final performance requirements. The assembly and adjustment process involves numerous variables that are difficult to control.

[0017] A physical image of the domestically designed all-glass fiber optic collimator FIOS, as shown below. Figure 6 As shown. This all-glass fiber optic collimator (FIOS) consists of an aspherical lens, two trapezoidal glass blocks, a titanium alloy stress-relieving block, and a pigtail protective sleeve. It is simpler than the all-glass fiber optic collimator (FIOS) designed abroad, but it has major defects in the assembly and adjustment method: 1. The problem of center alignment between the fiber ceramic ferrule and the aspherical lens; 2. The problem of focusing the aspherical lens.

[0018] Figure 7 This is a model diagram of the system. The focusing method involves changing the relative positions of two small trapezoidal glass blocks, thereby altering the distance between the lens and the ceramic ferrule end face, and ultimately adjusting the FIOS to meet the specified requirements. Figure 7 The diagram illustrates adjusting an aspherical lens to bring it closer to the ceramic ferrule. The trapezoidal glass block is moved upwards while the aspherical lens is moved downwards, bringing it closer to the ceramic ferrule. However, this adjustment method requires the aspherical lens to be installed first and aligned with the center of the ceramic ferrule before the optical characteristics of the FIOS can be measured. If the optical characteristics are unsatisfactory, the displacement of the two trapezoidal blocks needs to be readjusted to change the distance between the aspherical lens and the end face of the ceramic ferrule. However, moving the trapezoidal blocks causes the axis of the aspherical lens to shift from the center of the ceramic ferrule, requiring readjustment of the coaxiality between the ceramic ferrule and the aspherical lens. Therefore, the aspherical lens cannot be limited at the trapezoidal blocks. Consequently, it is difficult to align the axis of the aspherical lens with the center of the ceramic ferrule. There is also no limiting device between the two trapezoidal blocks, making position control difficult during movement. Meanwhile, during the dispensing and curing process, since there are no limiting positions for any of the components, it is difficult to maintain a stable relative position between the two trapezoidal blocks and between the trapezoidal block and the aspherical lens. This greatly increases the difficulty of assembling and adjusting FIOS and reduces the success rate of assembly and adjustment. Summary of the Invention

[0019] The present invention aims to solve the technical problems in the prior art and provide an all-glass fiber collimator for gravitational wave detection.

[0020] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0021] An all-glass fiber optic collimator for gravitational wave detection includes, from left to right, the following components arranged sequentially along the optical path: a pigtail protective sleeve, a titanium alloy stress-relieving block, a glass structural component, and an aspherical lens; the pigtail protective sleeve, the titanium alloy stress-relieving block, and the glass structural component each have a hollowed-out center to allow light to pass through.

[0022] The titanium alloy stress-relieving block and the glass structural component are connected together by a ceramic insert.

[0023] The right end of the glass structure is provided with a lens limiting end face; the left side of the aspherical lens is in contact with the lens limiting end face; the center of the right side of the aspherical lens is the origin of the coordinate system.

[0024] The ceramic ferrule adjusts its depth of insertion into the glass structure and its distance from the left side of the aspherical lens to achieve focusing of the all-glass fiber optic collimator.

[0025] In the above technical solution, the bottom surface of the glass structure is a plane.

[0026] In the above technical solution, the titanium alloy stress relief block is provided with a protrusion that restricts the insertion position of the tail fiber protective sleeve.

[0027] In the above technical solution, the hole at the right end of the glass structure where the aspherical lens is installed is coaxial with the hole at the left end where the ceramic insert is installed.

[0028] The present invention has the following beneficial effects:

[0029] The all-glass fiber collimator of this invention, applied to gravitational wave detection, can simultaneously satisfy multiple different working distances in an inter-satellite laser interferometry system, and the effective spot diameter of the Gaussian beam is completely smaller than the diameter of the photodetector. The wavefront difference of the Gaussian beam at each different working distance satisfies the interference conditions of a coherent beam, resulting in interference phenomena. Attached Figure Description

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0031] Figure 1 This is a schematic diagram of the internal interference optical path for testing the quality of an all-glass laser interferometer in the prior art.

[0032] Figure 2This is a schematic diagram of the internal optical path of the first FIOS-emitted beam used in existing technology within a scientific interferometer.

[0033] Figure 3 This is a schematic diagram of the optical path of a reference interferometer in an existing all-glass laser interferometer.

[0034] Figure 4 and Figure 5 These are schematic diagrams of the FIOS (Fiber Optic Optical System), a finished all-glass fiber collimator designed abroad in the existing technology.

[0035] Figure 6 This is a schematic diagram of the FIOS, a domestically designed all-glass fiber optic collimator in the existing technology.

[0036] Figure 7 This is a model diagram of the FIOS, a domestically designed all-glass fiber optic collimator in the existing technology.

[0037] Figure 8 and Figure 9 These are the interference pattern diagrams of the two photodetectors on the reference interference optical path.

[0038] Figure 10 and Figure 11 These are interference pattern images of the two photodetectors on the interference optical path used for testing quality.

[0039] Figure 12 and Figure 13 The images show the light spot patterns observed on the photodetector when the received flat-top beam is deflected by 0.1°.

[0040] Figure 14 This is a schematic cross-sectional view of the all-glass FIOS of the present invention.

[0041] Figure 15 This is a model diagram of the all-glass fiber collimator FIOS of the present invention.

[0042] Figure 16 and Figure 17 The images shown are actual photos of the all-glass fiber optic collimator FIOS from different angles.

[0043] The reference numerals in the figure are:

[0044] 1-Fiber optic protective sleeve; 2-Titanium alloy stress relief block; 3-Ceramic ferrule; 4-Glass structural component; 5-Aspherical lens; 6-Bottom surface of glass structural component; 7-Lens limiting end face; 8-Coordinate origin. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings.

[0046] To verify the design's suitability, physical optics simulation was used to examine the interference phenomenon of the two all-glass FIOS optical systems after multiple beam splitting and combining. The simulation also demonstrated the interference fringes of the two interfering beams on different photodetectors. Furthermore, the assembly and adjustment method for the all-glass fiber optic collimator (FIOS) was outlined, enabling convenient and rapid product design and installation. Based on the design requirements, the optical parameters of the designed optical system are as follows:

[0047] Table 1 Optical parameters of the optical system

[0048]

[0049]

[0050] The design results are shown in Table 2.

[0051] Table 2

[0052]

[0053] For the working distances in Table 2, the origin is taken as the vertex of the second surface of the aspherical lens, and the direction of light propagation is positive. Figure 14 As shown, calculate the light spot information at 10 distances between the position of the photodetector and the two vertices of the surface.

[0054] The beam waist position is indicated by marking the beam waist position relative to the photoelectric detection surface at the corresponding working distance, with the direction of beam propagation being positive. A negative sign indicates the beam waist to the left of the photoelectric detection surface, and a positive sign indicates the beam waist to the right of the photoelectric detection surface.

[0055] The Gaussian spot radius refers to the effective radius of the Gaussian beam at 1 / e of the peak energy of the Gaussian beam on the photosensitive surface of the photodetector at the working distance.

[0056] The wavefront curvature of a Gaussian beam refers to the radius of the wavefront surface formed by the equiphase surfaces of the Gaussian beam at the corresponding working distance.

[0057] The calculation results show that the effective radius of the Gaussian beam at 10 different working distances is less than 0.6 mm, which meets the design requirements of the optical system.

[0058] When two interfering beams meet and interfere on the photosensitive surface of a photodetector, one of the Gaussian beams is incident perpendicularly to the center of the photodetector and used as the reference beam. The other interfering beam is tilted at 0.05° and used as the measurement beam, interfering with the reference beam on the photosensitive surface of the photodetector.

[0059] Simulation results of interference beams: Interference phenomena on 6 photodetectors at 10 different working distances were simulated. The interference fringes on the photosensitive surface are shown in the following figures: The interference spots of the two photodetectors in the reference interference path are shown in the following figures. Figure 8-11 As shown.

[0060] The interference spots on the two photodetectors in the scientific interference optical path. When the received flat-top beam is deflected by 0.1°, the observed spot pattern on the photodetectors is as follows. Figure 12 and Figure 13 As shown.

[0061] Significant interference was observed on all six photodetectors, meeting the usage requirements. The optical system design was satisfactory.

[0062] A cross-sectional view of the all-glass fiber collimator (all-glass FIOS) for gravitational wave detection of the present invention is shown below. Figure 14 As shown.

[0063] The all-glass fiber collimator of the present invention for gravitational wave detection, such as Figure 14 As shown, the structure includes, in the optical path direction from left to right: a fiber optic protective sleeve 1, a titanium alloy stress-relieving block 2, a glass structural component 4, and an aspherical lens 5; the center of the fiber optic protective sleeve 1, the titanium alloy stress-relieving block 2, and the glass structural component 4 are all hollow structures to allow light to pass through; the hole at the right end of the glass structural component 4 where the aspherical lens 5 is installed is coaxial with the hole at its left end where the ceramic ferrule 3 is installed.

[0064] The titanium alloy stress-relieving block 2 and the glass structural component 4 are connected together by a ceramic ferrule 3; the right end of the glass structural component 4 is provided with a lens limiting end face 7; the left side of the aspherical lens 5 is in contact with the lens limiting end face 7; the center of the right side of the aspherical lens 5 is the coordinate origin 8; the ceramic ferrule 3 adjusts its distance from the left side of the aspherical lens 5 by adjusting the depth of insertion into the glass structural component 4, so as to complete the focusing of the all-glass fiber collimator.

[0065] The bottom surface 6 of the glass structural component 4 is flat, making it suitable for bonding to the interferometer glass substrate. The titanium alloy stress-relieving block 2 has a protrusion that restricts the insertion position of the fiber optic protective sleeve 1.

[0066] In the all-glass fiber optic collimator for gravitational wave detection of this invention, during fabrication, it is necessary to ensure that the hole for mounting the aspherical lens 5 in the glass structure 4 is coaxial with the circular hole for mounting the ceramic ferrule 3. During assembly, the aspherical lens 5 is installed in the designated position in the glass structure 4. Since the glass structure 4 has a limit on the aspherical lens 5, fine-tuning the position of the aspherical lens 5 ensures that the axis of the collimating lens is in a reasonable position. The axis of the aspherical lens 5 is aligned with the axis of the cylindrical hole in the glass structure 4 where the ceramic ferrule 3 is placed; at this point, adhesive is applied to fix the aspherical lens 5. The ceramic ferrule 3 is inserted into the designated position in the glass structure 4, ensuring that the center of the ceramic ferrule 3 coincides with the axis of the aspherical lens 5. By adjusting the insertion depth of the ceramic ferrule 3 into the glass structure 4, the focusing of the fiber optic collimator is completed. After changing the distance between the end face of the ceramic ferrule 3 and the rear surface of the aspherical lens 5, and ensuring that the optical technical specifications of the all-glass fiber optic collimator (FIOS) meet the usage requirements, adhesive is applied to fix the ceramic ferrule 3. Install titanium alloy stress-relieving blocks 2 and fix them with adhesive; install pigtail protective sleeve 1 and fix it with adhesive. The completed model of the all-glass fiber optic collimator FIOS is shown below. Figure 15 As shown, the actual product images are as follows: Figure 16 and Figure 17 As shown.

[0067] The all-glass fiber collimator of this invention, applied to gravitational wave detection, can simultaneously satisfy multiple different working distances in an inter-satellite laser interferometry system, and the effective spot diameter of the Gaussian beam is completely smaller than the diameter of the photodetector. The wavefront difference of the Gaussian beam at each different working distance satisfies the interference conditions of a coherent beam, resulting in interference phenomena.

[0068] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An all-glass fiber collimator for gravitational wave detection, characterized in that, The optical path includes, from left to right, the following components arranged sequentially: a fiber optic protective sleeve (1), a titanium alloy stress-relieving block (2), a glass structural component (4), and an aspherical lens (5); the center of the fiber optic protective sleeve (1), the titanium alloy stress-relieving block (2), and the glass structural component (4) are hollow structures to allow light to pass through; The titanium alloy stress-relieving block (2) and the glass structural component (4) are connected together by a ceramic insert (3); The glass structure (4) has a lens limiting end face (7) on its right end; the left side of the aspherical lens (5) is in contact with the lens limiting end face (7); the center of the right side of the aspherical lens (5) is the origin of coordinates (8). The ceramic ferrule (3) adjusts its depth of insertion into the glass structure (4) and its distance from the left side of the aspherical lens (5) to complete the focusing of the all-glass fiber collimator.

2. The all-glass fiber collimator for gravitational wave detection according to claim 1, characterized in that, The bottom surface (6) of the glass structural component (4) is a plane.

3. The all-glass fiber collimator for gravitational wave detection according to claim 1, characterized in that, The titanium alloy stress relief block (2) is provided with a protrusion that restricts the insertion position of the tail fiber protective sleeve (1).

4. The all-glass fiber collimator for gravitational wave detection according to any one of claims 1-3, characterized in that, The hole at the right end of the glass structure (4) where the aspherical lens (5) is installed is coaxial with the hole at the left end where the ceramic ferrule (3) is installed.

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