Study On The Gas Sensing Character Of Photonic Crystal Fibers

Photonic crystal fiber(PCF) as one of the focus that studied by many people in the photoelectron fields, including the characters,guide-light mechanism and fabrication. The application of PCF is also studied as the focus. This paper gives PCF application in the gases sensing at the theory and the experiment.Firstly, the theory of the index guiding PCF gases sensing is analyzed. The fraction of the power located in the holes is a very important parameter. The relation of this fraction with the parameters of PCF is calculated. The confinement loss is also analyzed. This analysis gives the theory basic for improving the sensitivity of the gases sensing.Secondly, by analyzing the theory of photonic bandgap, we find that the fraction of the power located in the hollow-core will be improved when the wavelengths located in photonic bandgap. The sensitivity of the hollow-core PCF will be higher than the index guiding PCF in the gases sensing. We study on the bandgap characters of the hollow-core PCF. A new kind of method which can be expressed as the bandgap-the power ratio of the core-hole is put forward. The analysis of photonic bandgap gives the theory basic for hollow-core PCF used in the gases sensing.Finally, in the detection experiment aspects, we put the methane in the hollow-core PCF and then detect the transmission spectrum of the PCF. The methane has the absorbed apex at 1600nm. We can judge the methane existence by the absorbed spectrum. The transmission spectrum of the PCF which is full with the methane and without the methane is detected. The experiment result is accord with the theory.