A method for manufacturing a micro-probe fiber Fabry-Perot interferometer based on femtosecond laser engraving a reflecting surface

Abstract

The application belongs to the technical field of optical fiber device manufacturing, and discloses a kind of micro probe type optical fiber Fabry-Perot interferometer (FPI) manufacturing method based on femtosecond laser engraving reflecting surface. Single-mode fiber taper, discharge fusion and femtosecond laser engraving reflecting surface method are used to manufacture micro probe type FPI. The size of micro probe can be controlled by adjusting the discharge intensity, discharge time and discharge frequency of fusion machine, the moving time and moving distance of two electrodes. The shape of the embedded reflecting surface in the micro probe can be controlled by adjusting the frequency, wavelength and power of femtosecond laser and the engraving path. This method can obtain compact structure, mass production, stable performance micro probe type Fabry-Perot interferometer, which plays a crucial role in the production and application process of Fabry-Perot based interferometric fiber sensor. In addition, micro probe type FPI can be used for high temperature, refractive index, humidity and other parameter detection.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber device manufacturing, and relates to a micro probe type optical fiber Fabry-Perot interferometer (FPI) manufacturing method based on femtosecond laser engraving of a reflecting surface. BACKGROUND

[0002] The sensors used in special environments such as power switch cabinets, cable slots, transformer windings and oil transmission pipelines need to have the characteristics of high insulation strength, anti-electromagnetic interference, small size, high sensitivity, corrosion resistance and stable performance, but traditional electronic sensors are difficult to have all these characteristics at the same time. In the past three decades, optical fiber sensors have rapidly risen in some special fields due to their inherent characteristics and advantages. In order to increase the flexibility of the sensing structure and improve the key performance indicators of the optical fiber sensor, femtosecond laser has attracted the research interest of many scholars. Femtosecond laser can realize multi-parameter and high-precision simultaneous measurement on smaller sensors due to its small thermal influence area, high machining precision, high machining efficiency and the ability to realize the fabrication of true three-dimensional structures. In recent years, the preparation methods of Fabry-Perot interferometer have been reported in many literatures, which can be mainly divided into three kinds. The first method is to use special optical fibers such as hollow optical fibers and photonic crystal fibers. Undoubtedly, the use of special optical fibers will greatly increase the preparation cost of the sensor. In addition, it is difficult to ensure that the length of the cut special optical fiber is consistent with the target length during the manual cutting of the special optical fiber, and the repeatability of the sensor preparation is poor. The second method is chemical etching. However, chemical etching has certain danger, a long preparation period and difficulty in accurately controlling the length of the microcavity. The third method is to use femtosecond laser to ablate microcavities or microchannels in a single-mode optical fiber, but the mechanical strength of the single-mode optical fiber is seriously damaged during the ablation process, and the cavity is easily damaged. Therefore, how to realize the safe and high-repetitive preparation of low-cost and stable performance Fabry-Perot interferometer has become a key research direction in the field of optical fiber FPI device manufacturing technology. SUMMARY

[0003] The present application solves the problems of difficulty in manufacturing, poor mechanical strength and unstable performance of optical fiber micro FPI, and provides a compact, mass-producible and stable micro probe type Fabry-Perot interferometer, which plays a crucial role in the production and application of Fabry-Perot based interferometric fiber sensors. The micro probe type FPI is manufactured by using single mode fiber tapering, discharge welding and femtosecond laser writing reflective surface method. The size of the micro probe can be controlled by adjusting the discharge intensity, discharge time, discharge frequency, moving time and moving distance of the two electrodes of the welding machine. The shape of the reflective surface embedded in the micro probe can be controlled by adjusting the frequency, wavelength and power of the femtosecond laser and the writing path.

[0004] The specific technical scheme of the present application is:

[0005] A micro probe type fiber Fabry-Perot interferometer manufacturing method based on femtosecond laser writing reflective surface, comprising the following steps:

[0006] (1) Discharge tapering at the axial center of the single mode fiber, move one side clamp of the welding machine to make the taper waist center deviate from the discharge center, discharge tapering again, and fuse to obtain a large diameter single taper fiber and a small diameter single taper fiber;

[0007] (2) Replace the small diameter single taper fiber with a single mode fiber with flat end face, adjust the position of the large diameter single taper fiber and the replaced single mode fiber, discharge welding, and with the increase of the discharge times, the taper waist of the taper fiber gradually becomes smaller until it is disconnected, and a micro probe appears on the end face of the single mode fiber;

[0008] (3) The single mode fiber with the micro probe is placed on the three-dimensional moving platform of the femtosecond laser, the power, frequency, wavelength and spot moving path of the femtosecond laser are set, the reflective surface of the FPI is written in the micro probe, and a micro probe type fiber Fabry-Perot interferometer with target parameters is obtained.

[0009] The discharge operation in steps (1) and (2) and the clamp movement in step (1) are completed by the welding machine.

[0010] The writing of the reflective surface in step (3) is completed by the femtosecond laser.

[0011] The present application has the following advantages:

[0012] (1) In the present application, the tapering is performed by the welding machine, and the discharge intensity, discharge time, discharge frequency, moving time and moving distance of the two electrodes can be flexibly controlled by the program.

[0013] (2) The taper optical fiber is fused to the end face of the single-mode optical fiber by using a fusion machine in the application, and the positions of the taper optical fiber and the single-mode optical fiber, the discharge intensity and the discharge times can be flexibly controlled.

[0014] (3) The preparation of the reflecting surface in the application uses a femtosecond laser writing method, has high mechanical strength, flexible design, and high preparation repeatability. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a schematic diagram of a microprobe manufacturing method based on single-mode optical fiber discharge tapering and fusing, wherein (a) is a single-mode optical fiber first discharge tapering effect diagram; (b) is a diagram of the relative positions of the taper waists after the clamp of the fusion machine is moved; (c) is a single-mode optical fiber second discharge tapering effect diagram; (d) is a diagram of replacing a smaller-diameter single-side taper optical fiber with a single-mode optical fiber with a flat end face; (e) is a diagram of the initial positions of the single-mode optical fiber and the larger-diameter single-side taper optical fiber; and (f) is a discharge fusing effect diagram of the single-mode optical fiber and the single-side taper optical fiber.

[0016] Figure 2 is a microscope diagram of probes of different sizes, (a) the probe length is 104 μm, (b) the probe length is 143 μm, (c) the probe length is 181 μm, and (d) the probe length is 231 μm.

[0017] Figure 3 is an effect diagram of reflecting surfaces constituted by FPIs engraved in the microprobe by using a femtosecond laser.

[0018] Figure 4 is a microprobe FPI interference spectrum of a probe with a length of 181 μm and a distance of 50 μm between the two reflecting surfaces. DETAILED DESCRIPTION

[0019] To make the above-mentioned purpose and advantages more understandable, the application is further described below in combination with the drawings and specific embodiments.

[0020] The specific implementation process of the application is as follows:

[0021] In the process of preparing the microprobe, first, the single-mode optical fiber is subjected to first discharge tapering in the fusion machine, and the fusion machine parameters are set as follows: discharge time 5000 ms, discharge intensity 3 unit, Z-axis pushing type two-side optical fiber, Z-axis pulling start time 3000 ms, Z-axis pulling distance 1000 μm, and the first tapering effect is as shown in (a). Figure 1 Then, the right optical fiber clamp is opened, and the left clamp is moved 200 μm to the left, and the optical fiber position after the movement is as shown in (b). Figure 1 Subsequently, second discharge tapering is performed, the taper waist is fused, and a smaller-diameter single-side taper and a larger-diameter single-side taper are obtained. Figure 1As shown in (c), the smaller diameter single-sided taper is replaced with a single-mode fiber with a flat end face. The positions of both are adjusted so that the end face of the single-mode fiber is 100 μm from the discharge center, and the single-sided taper fiber is tightly attached to the single-mode fiber, as shown in (c). Figure 1 As shown in (e). During the melting cone operation, micro probes of different lengths can be obtained by setting the Z-axis pulling distance during the discharge process. In the process of writing the reflective surface, the parameters of the femtosecond laser are first set as follows: wavelength 520nm, frequency 5kHz, power 2.5μW, and the moving speed of the high-precision micro-displacement stage is 30μm / s. Then, the spot movement path is set, and 50 reflective lines with a spacing of 0.5μm are written from bottom to top using a line-by-line method to form a reflective surface. Then, the micro-displacement stage is moved 50μm along the Y-axis, and another reflective surface is written using the same method.

[0022] Depend on Figure 2 It can be seen that as the Z-axis pulling distance increases, the probe length tends to increase. Figure 2 The paper presents physical images of microprobes with probe lengths of 104 μm, 143 μm, 181 μm, and 231 μm, respectively. Figure 3 The image shows a physical model of the micro-probe FPI after the reflective surfaces have been inscribed. When the probe length is 181 μm and the distance between the two reflective surfaces is 50 μm, the interference spectrum formed by the micro-probe FPI is as follows: Figure 4 As shown, the maximum fringe contrast is 5.02 dB, and the free spectral range is 11 nm. Therefore, this method can be used to achieve the mass production of compact and stable microprobe FPIs.

Claims

1. A method for fabricating a miniature probe-type fiber Fabry-Perot interferometer based on femtosecond laser-written reflective surfaces, characterized in that, It comprises the following steps: (1) discharging tapering at the axial center of a single-mode optical fiber, moving one side clamp of a fusion splicer to make the waist center deviate from the discharge center, discharging tapering again, and fusing to get a large-diameter one-side tapered optical fiber and a small-diameter one-side tapered optical fiber; (2) replacing the small-diameter tapered optical fiber with a single-mode optical fiber with flat end face, adjusting the positions of the large-diameter tapered optical fiber and the replaced single-mode optical fiber, discharging and fusing, and with the increase of the discharging times, the tapered waist of the tapered optical fiber gradually becomes smaller until it is disconnected, and a micro probe with small diameter and short length appears on the end face of the single-mode optical fiber; (3) the single-mode optical fiber with the micro probe is placed on a three-dimensional moving platform of a femtosecond laser, the power, frequency, wavelength and spot moving path of the femtosecond laser are set, the reflecting surface of a Fabry-Perot interferometer is inscribed in the ultra-short micro probe, and an ultra-short micro probe type fiber Fabry-Perot interferometer of the target parameter is obtained.

2. The method for making a micro-probe fiber Fabry-Perot interferometer based on femtosecond laser inscribed reflective surface according to claim 1, wherein, The discharging operations in steps (1) and (2) and the clamp moving in step (1) are completed by a fusion splicer.

3. The method for making a micro-probe fiber Fabry-Perot interferometer based on femtosecond laser inscribed reflective surface according to claim 1 or 2, characterized in that, The inscribing of the reflecting surface in step (3) is completed by a femtosecond laser.

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