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

Abstract

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.

Analytical modeling of the gas-filling dynamics in photonic crystal fibers

“…Combined with the ability to engineer their physical and optical properties, PCFs are attractive candidates for realizing chemical sensors and gas cells [1][2][3]. For instance, solid-core microstructured fibers can be designed to have specific dispersion characteristics or to have maximum overlap between the optical field and the gas species [4,5]. Applications such as acetylene gas spectroscopy and liquid chemical sensing have been successfully performed in suspended-core fibers where up to 29% of the optical power is available for sensing via the evanescent field [6,7].…”

Photonic Crystals

“…However, it should be noted that most research in the area of PhCs is related to the study of PhC fi bers (PCFs) (Hoo et al 2003 ;Fini 2004 ;Li et al 2007 ;Frazao et al 2008 ;Skorobogatiy 2009 ) . PCFs are two-dimensionally periodic PhCs fabricated using fi ber draw techniques developed for communications fi ber.…”

Enhanced spontaneous Raman scattering and gas composition analysis using a photonic crystal fiber

“…The stimulated Raman exponential gain coefficient depends on ðP=AÞL (pump power P per unit area A times interaction length L) and is enhanced in the HC-PBF system by the small pump beam crosssectional area and long fiber length [23]. Absorption measurement sensitivities are also increased by the long lengths possible when a HC-PBF absorption cell is employed [24]. The signal enhancement realized when a HC-PBF is used to contain the Raman medium and to collect the spontaneous Raman emission is of a somewhat different character.…”