Modal interferometer based on volatile organic compounds diffused in a simplified hollow-core photonic crystal fiber

摘要

In this paper, a modal interferometer based on a simplified hollow-core PCF, which diffused with volatile organic compounds (VOCs) in the air holes, is proposed and investigated in our experiment. When light travels through the input single mode fiber and transmits into the simplified hollow-core PCF, there is only fundamental core mode. However, the high-order core modes will be excited when the molecules of VOCs diffuse into the air holes. After propagation of these modes in the simplified hollow-core PCF, they will recombine at the exit single mode fiber. The ethanol is chosen as the VOC sample in our experiments. The interference pattern of the interferometer, based on a 5.1 cm long simplified hollow-core PCF, exhibited fringe spacing of ～30 nm. The transmission intensity decreases while the fringe visibility increases as the ethanol concentration becomes larger, and the interference spectrum of the ethanol-diffused simplified hollow-core PCF modal interferometer has a red-shift, from 1542.96 nm at 250 ppm to 1545.52 nm at 1000 ppm. The modal interference proposed above has great potential as an optical fiber sensor, measuring physical parameters such as the concentration of VOCs.