Volatile organic compound detection using twin-core photonic crystal fiber with selectively sealed air holes in-reflection interferometer

We present volatile organic compound (VOC) detection using modified twin-core photonic crystal fiber (TC-PCF) in-reflection interferometer. TC-PCF readily serves as an interferometer when light is launched into two cores along their common polarization axis. With manual gluing and subsequent infiltration technique, the air holes surrounding one core of TC-PCF are selectively sealed. Therefore, upon exposing in-reflection interferometer in proposed configuration to VOC, the vapor diffusion into the cladding air holes surrounding the other core induces a phase shift in its core mode only, and hence greatly enhances the vapor detection sensitivity of the TC-PCF. The detection limit of our device is measured to be 4.71×10^-10 moles for acetone.