耦合型微纳光纤偏振滤光器研究

微纳光纤偏振滤光器是光纤通信和传感系统的微型基本元件之一。利用超模耦合理论研究表明,当选择合适的耦合区长度和微纳光纤直径时,两平行紧贴微纳光纤构成的耦合器件可实现起偏效应,即将非偏振的输入光变为偏振光输出;理论设计分析给出了产生这种效应的几何参量值。实验研究了两根微纳光纤平行耦合时输出光偏振度(DOP)与耦合长度的关系,验证了起偏效应并制作了基于消逝场耦合的微纳光纤偏振滤光器。实验表明当微纳光纤偏振滤光器输入非偏振光时,在1545～1560nm波段耦合输出端光的偏振度达到了90%以上,实现了光束起偏;在此波段内某些波长的输出光消光比(LPER)可达到24dB以上,而其他波长处为椭圆偏振光或者圆偏振光,实现了分色起偏。此器件与检偏器组合可制成带通(阻)波长滤波器。

All Micro-Fiber Polarization Filter Based on Evanescent Field Coupling

Micro fiber polarization filter is one of micro basic components for optical communication and sensors system. Theoretical analysis based on super mode theory shows that polarizing effect in coupling component of two contacted micro fibers can be achieved when the fibers′ coupling length and diameters are chose suitably, which means unpolarized light can be changed into polarized light after it is through the coupling micro fiber component. Theoretical analysis and design give the geometric parameters for the polarizing effect. Experiments are made to investigate the relationship between degree of polarization (DOP) of the output light and coupling length when two micro fibers are lined parallel to couple. Micro fiber polarization filers based on evanescent field are manufactured. Experiments show that the (DOP) of the output light within the wavelength band of 1545~1560 nm in the micro fiber polarization filers are higher than 90% when the unpolarized light is input, which means the light is polarized. The linear polarization extinction ratio (LPER) of output light at some wavelengths with the band are higher than 24 dB, while output lights at another wavelengths are elliptical or circular polarized light. It means that output lights are polarized according to their wavelengths. The micro component can construct the band-pass wavelength fiber when it is used with an optical polarizer.