Method for preparing phase shift optical fiber bragg grating based on femtosecond laser direct writing

A fiber Bragg and femtosecond laser technology, applied in the field of fiber optics and nonlinear optics, can solve the problems of inability to precisely control the size of the phase shift, time-consuming, etc., and achieve the effect of reducing precision requirements, simple operation, and high processing accuracy

Active Publication Date: 2017-01-04
XI AN JIAOTONG UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This method uses a focused femtosecond laser to write out the periodic structure of the phase-shifted FBG one by one. Since the period of the phase-shifted FBG is usually below a few microns, this method requires the processing platform to have sub-micron scale precision and long-term high Stability, and this method takes a long time to prepare FBG with a large length
In addition, it was found that when FBG is prepared by using femtosecond laser and uniform periodic phase mask, the phase shift will also occur through two irradiations, but this method cannot accurately control the magnitude of the phase shift

Method used

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  • Method for preparing phase shift optical fiber bragg grating based on femtosecond laser direct writing
  • Method for preparing phase shift optical fiber bragg grating based on femtosecond laser direct writing
  • Method for preparing phase shift optical fiber bragg grating based on femtosecond laser direct writing

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Experimental program
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Effect test

Embodiment 1

[0032] This embodiment takes processing a high-temperature F-P temperature sensor as an example, as follows:

[0033] Original material: Fiber Bragg Grating

[0034] The preparation steps of FBG with phase shift structure are described in detail as follows:

[0035] (1) Fix the fiber Bragg grating 1 on a glass slide, and add a refractive index matching solution to the grating area, and then cover it with a cover glass, such as figure 1 shown;

[0036] (2) Place the fixed fiber Bragg grating 1 on the three-dimensional electric translation platform 5, such as figure 1 shown. The repetition frequency of the femtosecond laser 3 is 1000 Hz, the pulse width is 50 fs, and the power is set at 0.7 mW. A microscopic objective lens 2 with 20× and a numerical aperture of 0.45 is selected to focus the femtosecond laser 3 near the core of the fiber Bragg grating 1 through the microscopic objective lens 2 . The scan rate of the three-dimensional electric translation stage 5 is 20 μm / s. ...

Embodiment 2

[0041] Original material: Fiber Bragg Grating.

[0042] (1) Fixing of the fiber Bragg grating 1 Refer to the corresponding process of the first embodiment.

[0043] (2) The process of femtosecond laser 3 scanning the optical fiber refers to the corresponding process of embodiment 1. The parameters are: the repetition frequency of femtosecond laser 3 is 1000 Hz, the pulse width is 50 fs, and the power is set to 2 mW; select 20 ×, numerical aperture 0.45 The microscope objective lens 2; the scanning rate of the three-dimensional electric translation stage 5 is 20 μm / s.

[0044] (3) Refer to Case 1 for the scanning method of the femtosecond laser. The scanning length is 1000 μm. After scanning the first straight line, move 0.8 μm vertically to scan the second line. A total of 14 lines are scanned to cover the entire fiber core area.

[0045] (4) Cleaning of the optical fiber after scanning by the femtosecond laser 3 refers to the corresponding process of Example 1.

[0046] F...

Embodiment 3

[0048] Original material: Fiber Bragg Grating.

[0049] (1) Fixing of the fiber Bragg grating 1 Refer to the corresponding process of the first embodiment.

[0050] (2) The process of femtosecond laser 3 scanning the optical fiber refers to the corresponding process of embodiment 1. The parameters are: the repetition frequency of femtosecond laser 3 is 1000Hz, the pulse width is 50fs, and the power is set to 8mW; select 5×, numerical aperture 0.15 The microscope objective lens 2; the scanning rate of the three-dimensional electric translation stage 5 is 195 μm / s.

[0051] (3) Refer to Case 1 for the scanning method of the femtosecond laser. The scanning length is 1500 μm. After scanning the first straight line, move 0.9 μm vertically to scan the second line. A total of 12 lines are scanned to cover the entire fiber core area.

[0052] (4) Cleaning of the optical fiber after scanning by the femtosecond laser 3 refers to the corresponding process of Example 1.

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Abstract

The invention provides a method for preparing phase shift optical fiber bragg grating based on femtosecond laser direct writing. The method comprises the following steps: performing fixed point radiation or scanning in a fiber core area of the optical fiber bragg grating of an ordinary structure by using focused femtosecond laser, forming one or more areas with changed refractive indexes in the fiber core area of the optical fiber bragg grating of the ordinary structure, and forming a phase shift structure, thereby obtaining the phase shift optical fiber bragg grating. Compared with the prior art, the method is relatively simple in processing procedure, high in processing speed and applicable to optical fiber of different materials, and precision control of phase shift within 0-2pi can be achieved. The phase shift optical fiber bragg grating prepared by using the method provided by the invention can be applied to fields of sensation, optical fiber laser and the like.

Description

technical field [0001] The invention belongs to the field of fiber optics and nonlinear optics, and relates to a processing method of a fiber Bragg grating (FBG) with a phase shift structure. Background technique [0002] The phase-shifted fiber Bragg grating (FBG) is formed by introducing a phase mutation at a specific position of a conventional FBG. The most common one is π-phase-shifted FBG, which can open a transmission window in the Bragg reflection band, making the grating have a higher selectivity for a certain wavelength, so it is often used as a narrowband bandpass filter. If multiple phase shift points are introduced in the grating, multiple transmission windows can exist in the Bragg reflection spectrum, which can be used for fiber multi-channel filters. For a single phase shift point phase shift FBG, the FBG divided into two sections and the intermediate phase shift region can form a resonant cavity. When the phase shift FBG is an active fiber with gain, it cons...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02B6/02
CPCG02B6/02147
Inventor 陈涛司金海李思佳杜勇侯洵
Owner XI AN JIAOTONG UNIV
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