A non-magnetic polarization maintaining optical fiber collimator

Abstract

The utility model provides a non -magnetic polarization -maintaining fiber collimator can realize efficient collimation output of linearly polarized light, and is applicable to strong magnetic field environment. The collimator includes non -magnetic sleeve, polarization -maintaining fiber with glass capillary and lens assembly, wherein, polarization -maintaining fiber is fixed in one end of non -magnetic sleeve through glue, and the lens assembly for collimating output input beam and keeping linear polarization characteristic is arranged in the other end of non -magnetic sleeve, polarization -maintaining fiber is polarization -maintaining fiber with FC / APC jumper connector of specific wavelength 795nm, total length is greater than or equal to 6m, extinction ratio is greater than 22db, and insertion loss is less than 1db. The lens assembly adopts plano -convex lens. Non -magnetic polarization -maintaining fiber collimator improves coupling efficiency and system stability and consistency.

Description

Technical Field

[0001] This utility model relates to the fields of optical communication technology and quantum precision sensing, specifically to a non-magnetic polarization-maintaining fiber collimator, which is suitable for high-precision optical systems, such as quantum communication, atomic magnetometers and high-end fiber optic sensing. Background Technology

[0002] (1) In existing fiber optic collimator technology, traditional collimator components are usually encapsulated in metal, ceramic, or ordinary plastic materials. However, metal materials are prone to introducing magnetic field interference in high-precision magnetic field measurements and quantum optics experiments, while ordinary plastic materials have low high-temperature resistance and mechanical strength, making it difficult to meet the requirements of high-end applications. Therefore, PEEK material is introduced as the collimator sleeve because it is non-magnetic, high-temperature resistant (260℃), corrosion resistant, and has high hardness (Vickers hardness 20-30), ensuring its stable performance in collimator assembly.

[0003] (2) Existing fiber collimators have certain shortcomings in terms of optical axis alignment accuracy, adhesive curing uniformity, and assembly efficiency. For example, the shrinkage of adhesive volume during the curing process may cause the fiber end face to tilt, affecting the collimation quality of the beam. Here, epoxy resin AB glue—EPO-TEK353ND—is used to optimize the curing process of the glue (temperature gradient optimization), slowly release its stress, and increase the Tg point; in addition, a side-wall perforated eccentric sleeve is designed and processed, which improves efficiency by 177% and greatly reduces the difficulty of lens assembly. Furthermore, the eccentric sleeve (3.7°) matches the 8° end face of the capillary, improving its optical axis alignment accuracy and reducing the eccentricity to below 0.5.

[0004] (3) Some collimators are prone to optical axis shift under extreme temperature conditions, which reduces the stability of the system. The thermal expansion coefficient of PEEK material is more compatible with that of 353ND glue, which can reduce optical axis shift caused by temperature changes.

[0005] Therefore, developing a non-magnetic, high-temperature resistant, and high-precision polarization-maintaining fiber collimator has significant engineering value and application prospects. This invention provides a novel assembly process for a non-magnetic polarization-maintaining collimator, achieving close-range collimation. It can be used in single-optical atomic magnetometer testing and optical communication, solving magnetic field interference, and its miniaturized design allows for richer and more sensitive signal acquisition.

[0006] This method is expected to be applied in fields such as electromagnetic induction imaging, biomagnetism, optical communication, quantum precision measurement, and geomagnetic observation. Utility Model Content

[0007] A non-magnetic polarization-maintaining fiber collimator is characterized by comprising a non-magnetic sleeve, a polarization-maintaining fiber with a glass capillary, and a lens assembly; wherein the polarization-maintaining fiber is fixed to one end of the non-magnetic sleeve by adhesive, and the lens assembly for collimating the input beam output and maintaining its linear polarization characteristics is disposed at the other end of the non-magnetic sleeve.

[0008] 2. Furthermore, the polarization-maintaining fiber is a specific wavelength 795nm polarization-maintaining fiber with FC / APC jumper connector, with a total length ≥6m, extinction ratio >22dB, and insertion loss <1dB.

[0009] 3. Furthermore, the lens assembly adopts a plano-convex lens.

[0010] 4. Furthermore, the non-magnetic sleeve adopts side wall perforation and adhesive application.

[0011] 5. Furthermore, the end face of the polarization-maintaining fiber glass ferrule is 8°; at the same time, a 3.7° eccentric sleeve is designed for angle compensation.

[0012] 6. Further, the eccentricity is <0.5° overall.

[0013] Advantages of this utility model:

[0014] 1. Non-magnetic packaging structure: PEEK material is used instead of traditional metal shell to avoid magnetic field interference, making it suitable for MRI equipment, quantum communication and magnetic field sensitive environments.

[0015] 2. High temperature and corrosion resistant design: PEEK material has long-term high temperature resistance (260℃) and excellent corrosion resistance, which is superior to ordinary plastics and metal packaging.

[0016] 3. Low thermal expansion matching: The thermal expansion coefficients of the lens, adhesive and sleeve are matched to each other, reducing optical axis drift caused by temperature changes and increasing axis accuracy and stability.

[0017] 4. Side wall perforation and eccentric structure design: One end is designed and machined with a positioning hole on the side wall of the sleeve. The lens is installed by applying adhesive to the side wall and then heating and curing it. Compared with the traditional method, the efficiency is increased by 220%, and the lens is less likely to fall out or break in the sleeve, increasing the safety of the product. The other end has a 3.7° eccentric inlet designed and machined at the glass capillary insertion point. The inlet is angled with the 8° end face of the capillary to reduce the collimator spot eccentricity to less than 0.5.

[0018] 5. Improved curing temperature for stress control of adhesive: Optimize the adhesive curing process (80℃-110℃) with gradient temperature increase to increase the Tg point and reduce the impact of stress release due to colloid shrinkage on optical axis stability.

[0019] 6. Improved sensitivity of alkali metal atomic magnetometers: The application of a single-optical, non-magnetic polarization-maintaining fiber collimator in a 64-channel array atomic magnetometer significantly reduces gas cell sensitivity to ~20 fT / Hz. 1 / 2 . Attached Figure Description

[0020] The embodiments of this utility model will be described in detail with reference to the accompanying drawings, wherein:

[0021] · Figure 1 An exploded view of the PEEK sleeve package structure is shown.

[0022] · Figure 2 The diagram shows the structure of the sleeve sidewall perforation and lens assembly position of this utility model.

[0023] · Figure 3 The blue sleeve is shown.

[0024] · Figure 4 The diagram shows an auxiliary optical axis alignment optimization and an eccentric assembly of the capillary and sleeve.

[0025] · Figure 5 The output of the eccentricity measurement after optimization by the Matlab algorithm is shown in the figure.

[0026] · Figure 6 A statistical dot plot of the sensitivity of a 16-channel alkali metal atomic magnetometer is shown. Detailed Implementation

[0027] A novel non-magnetic polarization-maintaining fiber collimator includes a non-magnetic sleeve made of PEEK material, a polarization-maintaining fiber with a glass capillary tube, and a plano-convex lens. The polarization-maintaining fiber is fixed to one end of the non-magnetic sleeve with adhesive, and the lens assembly is located at the other end of the non-magnetic sleeve. The lens is used to collimate the input beam and maintain its linear polarization characteristics. The entire structure is made of non-magnetic materials, making it suitable for magnetic field-sensitive environments, and it features a high extinction ratio and a large beam size.

[0028] 2. Furthermore, the polarization-maintaining optical fiber with FC / APC jumper connector at a specific wavelength of 795nm has a capillary material of high borosilicate glass, a total length of ≥6m, an extinction ratio of >22dB, an insertion loss of <1dB, and good polarization stability.

[0029] 3. Furthermore, the lens assembly includes a plano-convex lens made of K9 material. The radius of curvature and thickness of the lens have been optimized to match the numerical aperture (NA) of the polarization-maintaining fiber, thereby improving the collimated beam quality and maintaining the Gaussian width of the beam spot at 2.4 mm.

[0030] 4. Furthermore, the non-magnetic sleeve uses side wall perforation and adhesive application, which ensures the lens is securely fixed and does not fall off, while also facilitating assembly. Compared with inner wall spin coating, the efficiency is increased by 177%. Imported epoxy resin AB glue is used, and the curing process is optimized (such as gradient temperature baking curing), reducing the impact of glue shrinkage and thermal expansion on the alignment beam characteristics, ensuring that the lens will not break.

[0031] 5. Furthermore, the end face of the polarization-maintaining fiber glass ferrule is 8° to reduce loss; simultaneously, a 3.7° eccentric sleeve matching is designed for angle compensation, optimizing the optical axis alignment accuracy. Matlab code for fitting and error elimination is written to measure the eccentricity, with an overall accuracy of <0.5°. A high-precision optical alignment structure is used to ensure the stability of the collimated beam.

[0032] 6. A non-magnetic polarization-maintaining fiber collimator, characterized by: using a non-magnetic sleeve made of PEEK material to avoid magnetic field interference, making it suitable for magnetic field-sensitive environments such as MRI equipment, quantum communication, and atomic magnetometers, and applicable to alkali metal atomic magnetometers with sensitivity below 20 fT / Hz. 1 / 2 .

[0033] The specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0034] This invention provides a novel non-magnetic polarization-maintaining fiber collimator, capable of achieving efficient collimated output of linearly polarized light and suitable for strong magnetic field environments. The collimator comprises a lens + lens sleeve assembly and a polarization-maintaining fiber with a capillary glass ferrule. The assembly includes a K9 plano-convex lens 1, a non-magnetic lens sleeve 2, and a non-magnetic ferrule sleeve 3. The polarization-maintaining fiber is 6m long and includes an 8° end-face capillary 4 as the output end, a blue sleeve 5 (3mm), and an FC / APC polarization-maintaining jumper 6 as the input end, which helps reduce reflection interference. The collimator has a compact internal structure. The lens is made of K9 material and has a radius of curvature matching the numerical aperture, ensuring a stable output beam spot and a small divergence angle. The collimated beam width can reach 2.8mm, and the Gaussian width is maintained at 2.4mm. Angle compensation is achieved between the 8° capillary and the 3.7° eccentric sleeve, resulting in an eccentricity of <0.5 after fitting, improving coupling efficiency and system stability and consistency.

[0035] Example 1: Non-magnetic Encapsulation Design In this example, the collimator housing is made of PEEK material, with fiber optic fixing grooves formed through precision machining, and assembled using a non-magnetic bonding process. The use of PEEK material effectively avoids magnetic field interference, improving the collimator's applicability in magnetically sensitive applications.

[0036] Example 2: The thermal expansion coefficients of the lens, adhesive and sleeve are matched with each other to reduce optical axis drift caused by temperature changes and increase axis accuracy and stability, as shown in Table 1.

[0037] Material Chinese name Coefficient of thermal expansion (CTE) unit PEEK Polyetheretherketone <![CDATA[~47×10 -6 / ℃]]> µm / (m.℃) or ppm / ℃ 353ND glue Epoxy resin adhesive (EPO_TEK353ND) <![CDATA[~23×10 -6 / ℃]]> µm / (m.℃) HK9L Optical glass (equivalent to Schott N-BK7) <![CDATA[~7.1×10 -6 / ℃]]> µm / (m.℃)

[0038] Table 1

[0039] Example 3: Improved Sidewall Drilling and Adhesive Curing Process. This example optimizes the adhesive dispensing path and designs a sidewall-drilled sleeve. The lens is placed in the sleeve slot, and adhesive is dispensed through four circular holes on the sidewall and cured by gradient temperature increase (80°C for 1.5h, then 110°C for 0.5h), reducing the optical axis offset problem caused by adhesive shrinkage. Compared with the traditional method of spin coating adhesive on the inner wall of the sleeve (6min / pcs), manual sidewall drilling and dispensing takes 2min10s / pcs, improving efficiency by 177%, and is suitable for mass assembly of lens sleeves.

[0040] Example 4: Sleeve Eccentric Structure and Reduction of Eccentricity In this example, a 3.7° eccentric bevel is designed and machined at one end of the sleeve to compensate for the angle with the 8° end face of the fiber optic capillary, making the light spot nearly parallel to the optical axis and reducing eccentricity. Furthermore, the algorithm for measuring eccentricity has been optimized to eliminate the error caused by the collimator not being perfectly horizontal. After fitting, the overall eccentricity is <0.5, reaching the level of a qualified collimator product.

[0041] Example 5: Sensitivity Optimization of Atomic Magnetometers. The application of a single-optical, non-magnetic polarization-maintaining fiber collimator in a 64-channel array atomic magnetometer significantly reduces the gas cell sensitivity compared to traditional magnetometers (~20 fT / Hz). 1 / 2 ), a reduction of 4-7 fT / Hz per channel 1 / 2 The average sensitivity is 13-16 fT / Hz. 1 / 2 .

[0042] The non-magnetic polarization-maintaining fiber collimator employs PEEK packaging, precision optical axis alignment, and optimized adhesive curing process and assembly efficiency, improving product reliability and adaptability, and is particularly suitable for high-end optical systems.

Claims

1. A non-magnetic polarization maintaining optical fiber collimator characterized by, It includes a non-magnetic sleeve, a polarization-maintaining fiber with a glass capillary, and a lens assembly; wherein, the polarization-maintaining fiber is fixed to one end of the non-magnetic sleeve with glue, and the lens assembly, which is used to collimate the input beam and maintain its linear polarization characteristics, is set at the other end of the non-magnetic sleeve.

2. The magneto-optically neutral fiber collimator of claim 1, wherein: The polarization-maintaining fiber is a 795nm wavelength polarization-maintaining fiber with FC / APC jumper connectors, with a total length ≥6m, extinction ratio >22dB, and insertion loss <1dB.

3. The magneto-optically neutral fiber collimator of claim 1, wherein: The lens assembly uses a plano-convex lens.

4. The magneto-optically neutral fiber collimator of claim 1, wherein: The non-magnetic sleeve uses sidewall perforation and adhesive application.

5. The magneto-optically neutral fiber collimator of claim 1, wherein: The end face of the polarization-maintaining fiber optic glass ferrule is 8°; at the same time, a 3.7° eccentric sleeve is designed for angle compensation.

6. The magneto-optically neutral fiber collimator of claim 1, wherein: Eccentricity, overall <0.5°.

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