High Birefringence Photonic Crystal Fibers And The Temperature Sensing Characteristics

Photonic crystal fiber（PCF）is an optical fiber with axially oriented microstructure,it has many superior properties compared with traditional fibers,such as high birefringence,large numerical aperture,high nonlinearity,low confinement loss,etc.As a result of its unique optical properties,PCFs have many applications in the fields of optical communication,optical signal processing,and high-power transmission.In addition,due to the flexible design of the structure,PCFs have become a research hotspot in recent years.This thesis focuses on the birefringence,the nonlinearity and the temperature sensing characteristics of PCFs based on high birefringence.The main research contents are as follows:（1）A novel photonic crystal fiber with an elliptical tellurite core is proposed to simultaneously realize high birefringence,high nonlinearity,and low confinement loss.Vital properties of the PCF such as the birefringence,the nonlinearity,and the confinement loss have been investigated by employing the full vectorial finite element method.The results show that the birefringence and the nonlinear coefficient can be7.57?10^-2and 188.39W^-1k m^-1respectively at the wavelength of 1550nm,and the confinement loss is as low as10^-9dB/m.The proposed PCF have potential applications in fiber sensing,polarization-maintained transmission,and super-continuum generation.（2）An elliptical core photonic crystal fiber filled with silicon nano-crystal is designed to achieve ultra-high nonlinearity,large numerical aperture and high birefringence.The results demonstrate that at the wavelength of 1000nm,the fiber can obtain ultra-high nonlinear coefficients of 1.86×10⁶ W^-1·km^-1 and 1.79×10⁶ W^-1·km^-1 in X and Y polarizations,respectively.And at the wavelength of 3000nm,the numerical aperture can be 0.86 and 0.81 in X and Y polarizations,whereas the birefringence can be up to an order of 10^-1.In particular,it is worth noting that the air hole spacing has no effect on the performance of the PCF,which is very important in the production of the PCF.The PCF has important application in super-continuum generation and biomedical imaging.（3）A photonic crystal fiber is designed to achieve high temperature sensitivity.The fiber is based on the high birefringence,the air hole of the PCF was filled with temperature sensitive liquid ethanol selectively.The effects of different filling methods and structure parameters on the temperature sensitivity of the PCF are analyzed.It can be found that high temperature sensitivity of3.645?10^{-5 o} C^-1can be obtained based on the high birefringence PCF at the wavelength of 1550nm.The PCF has potential application value in the field of temperature sensing.