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Lyot filter based on circular polarizers

A filter and circular polarizer technology, which is applied in the field of optical signal processing and optical fiber sensing, can solve the problems of complex process, easy to be affected by the environment, etc., and achieve the effect of small environmental impact

Inactive Publication Date: 2016-05-18
HUAZHONG UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Aiming at defects such as alignment and adjustment of the optical path of filters in the prior art, being easily affected by the environment, etc., and complicated processes, the purpose of the present invention is to solve the above technical problems

Method used

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  • Lyot filter based on circular polarizers
  • Lyot filter based on circular polarizers
  • Lyot filter based on circular polarizers

Examples

Experimental program
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Effect test

Embodiment 1

[0021] Two fiber-optic circular polarizers with a working wavelength range of 1500-1600nm, such as chiral fiber grating (Chiral FiberGrating), etc., and the optical fiber between the two circular polarizers (Circular Polarizer) is a birefringent fiber, such as polarization maintaining fiber (PMFiber), The length is L meters, and the refractive index of the slow axis is n 1 , the fast axis refractive index n 2 , the refractive index difference is Δn, which constitutes a Lyot filter. figure 1 A schematic diagram of the structure is given. figure 2 gives Δn=6.7552×10 -4 The normalized transmission spectrum shape of Lyot filter under different length L.

Embodiment 2

[0023] This example is a two-stage cascaded Lyot filter, sharing 3 circular polarizers, and the i-th circular polarizer is CP i (i=1,2,3), CP i with CP i+1 Between them is a polarization maintaining fiber, denoted as PMFiber i , with length L i . The length of each segment of PM fiber satisfies, L 1 = 2L 2 . Fig. 3 gives a schematic diagram of the structure. Fig.4 gives the L 1 =0.4m,L 2 =0.2m, the output normalized spectrogram.

Embodiment 3

[0025] This example is a three-stage cascaded Lyot filter, sharing 4 circular polarizers, and the i-th circular polarizer is CP i (i=1,2,3), CP i with CP i+1 Between them is a polarization maintaining fiber, denoted as PMFiber i , with length L i . The length of each segment of PM fiber satisfies, L 1 = 2L 2 = 4L 3 , that is, the length of the cascaded polarization-maintaining fiber is 1:2:4:...:2i (i is the number of cascaded series), and the cascaded filter will have a larger sidelobe suppression ratio at this time. Figure 5 A schematic diagram of the structure is given. Image 6 gives L 1 =0.4m, L 2 = 0.2m, L 3 =0.1m, the normalized spectrogram output.

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Abstract

The invention discloses a Lyot filter based on circular polarizers, belonging to the optical signal treatment and fiber sensing field. The filter in the prior art need align and adjust a light path, is susceptible to environment influence, and has complex processes. The Lyot filter is provided with two polarizers at two ends, and the two polarizers are in birefringence fiber connection. An all-fiber structure and a fiber system are easy to integrate, and the transmitted spectrum of a largest rejection ratio can be realized without the angle adjustment between the polarizers and a birefringence fiber optical axis.

Description

technical field [0001] The invention belongs to the technical field of optical signal processing and optical fiber sensing, and more specifically relates to a Lyot filter based on a circular polarizer. Background technique [0002] The Lyot filter is a polarization interference filter proposed by Bernard Lyot in 1933. Its basic structure is to place a section of birefringent medium between two parallel linear polarizers, and the angle between the optical axis of the polarizer and the fast axis or slow axis of the birefringent medium is 45°. Then multiple Lyot filters are cascaded, named as filter. [0003] Lyot filters have been widely used in spectral imaging, optical communication, lasers and other fields. However, most of Lyot's filters are based on bulk devices. The disadvantage of bulk devices is that it requires careful alignment and adjustment of the optical path, and is susceptible to environmental vibrations, stray light, etc. The blocky structure also makes ...

Claims

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Application Information

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IPC IPC(8): G02B5/28
CPCG02B5/28
Inventor 舒学文杜岳卿
Owner HUAZHONG UNIV OF SCI & TECH
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