Lantian Hou

Study of the sensitivity of gas sensing by use of index-guiding photonic crystal fibers

We demonstrate an absorption transmission spectrum of CH(4) in a 16.9 cm long index-guiding photonic crystal fiber (PCF) fabricated in our laboratory. One of the main factors to improve the sensitivity is to increase the fraction of power in PCF cladding air holes. We study the fraction of power in PCF cladding air holes as a function of the index-guiding PCF parameters. We found that a PCF with small spacing and a large air-filling ratio has a higher fraction of power in its cladding air holes. At the same time the mode area in this PCF is small and would generate strong nonlinear effects in the fiber. If we use a PCF in which the core is formed by missing seven air holes, it is immediately obvious that the PCF used as a sensor has higher sensitivity and a larger mode area.

Improved fully vectorial effective index method in photonic crystal fiber

In the simulation of photonic crystal fibers, the fixed value of the normalized equivalent core radius (p/Lambda) in the fully vectorial effective index method is inaccurate. For what is believed to be the first time, the relation of p/Lambda with normalized frequency (Lambda/lambda) and hole-to-pitch ratio (d/Lambda) is obtained. The improved fully vectorial effective index method (IFVEIM) is proposed. The modal properties computed with the IFVEIM, such as the effective index and the total dispersion, are closely matched to those of the multipole method as well as to experimental values, and the errors of the effective index have been reduced by 2 to 3 orders of magnitude.

Study on highly nonlinear microstructured fibers

A highly nonlinear dispersion flattened microstructured fiber is proposed. The new structure adopts two claddings with different pitches, air-holes diameters and air-holes arrayed fashions. The characteristics of such microstructured fiber such as nonlinearity and dispersion properties are investigated. The influence of the cladding structure parameters on the nonlinear coefficient and geometric dispersion is analyzed by full-vector finite element method with perfectly matched layer. Highly nonlinear coefficient and the dispersion properties of fibers are tailored by adjusting the cladding structure parameters. A novel microstructured fiber with highly nonlinear coefficient and dispersion flattened which is suited for supercontinuum generation is designed.

Research on the sensing characteristics of photonic crystal fibers

It is well known that PCFs, compared with traditional fibers, have many special characteristics. Because of these, PCFs have been used in sensors. Based on the principles of traditional fiber sensors, this paper analyzes the probability of applications of PCFs in gas or liquid sensors. Due to the multi-hole properties of the PCFs, we can make some gas or liquid sensors by putting different gases or liquids into its air-hole. In this paper, the sensitivity of PCF sensors was simulated by the multipole method. By changing the core radius of PCFs or the gas fraction in the hole of PCFs, we can improve their sensitivity. Due to the superiority in their configuration, the research on PCF sensing characteristics will surely promote the development and application of the new-type sensors and other photoelectron devices.