[ Instrument R & D of Instrument Network ] Recently, the research team of the High Power Laser Unit Technology Laboratory of Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences has made new progress in the basic research of mid-infrared anti-resonant hollow fiber. The team carried out in-depth theoretical research on the fundamental problem of optical waveguides caused by the absorption of optical fiber materials, and established an analytical model of the international optical fiber material loss, and used this model to predict the quartz-based glass material at 4 microns mid-infrared Band loss limit.
Optical fiber is short for optical fiber. It is a fiber made of glass or plastic, which can be used as a light transmission tool. The transmission principle is total reflection of light. Gao Kun and George A. Hockham, former presidents of the Chinese University of Hong Kong, first proposed the idea that optical fiber can be used for communication transmission. Gao Kun won the 2009 Nobel Prize in Physics. It is divided into single-mode fiber, multi-mode fiber, special fiber, etc. It has the advantages of wide bandwidth, no crosstalk, and nuclear radiation resistance.
In recent years, anti-resonant hollow fiber (AR-HCF) has received widespread attention due to its broadband and low-loss transmission characteristics. Since most of the light is confined in the air core, the anti-resonant hollow core fiber can greatly overcome the influence of the absorption of the matrix material itself, and significantly reduce the material loss. At present, quartz glass is used to prepare anti-resonant hollow fiber, and the transmission loss of 0.04 dB / m is achieved at a wavelength of 4 microns, and the wavelength of quartz material absorbs more than 800 dB / m.
The hollow fiber is mainly used for energy transmission, which can be used for X-ray, ultraviolet and far infrared light energy transmission. There are two types of hollow fiber structures: First, the glass is made into a cylindrical shape, and the core and cladding principles are the same as the step type. Use light to propagate through the total reflection between air and glass. Because most of the light can be propagated in lossless air, it has the function of a certain distance. The second is to make the reflectivity of the inner surface of the cylinder close to 1, in order to reduce the reflection loss. In order to improve the reflectivity, there is a dielectric in the Jane to reduce the loss in the operating wavelength band. For example, a loss of several dB / m at a wavelength of 10.6pm can be achieved.
In this study, the researchers proceeded from the classic optical waveguide theory of Snyder and Love, extended the concept of modal overlap factor to the field of hollow fiber, and strictly deduced the semi-analytical expression of the modal overlap factor to characterize the hollow core Fiber material absorption contributes to transmission loss. The study compares the calculation results of semi-analytical expressions with the finite element method numerical calculation system, and proves the accuracy and effectiveness of the model. In addition, the principle of optimal design of low-loss anti-resonant hollow fiber under high material absorption conditions was systematically discussed, and the transmission limit of mid-infrared band quartz-based anti-resonant hollow fiber was predicted.
Source: Encyclopedia, Shanghai Institute of Optical Precision Machinery
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