3 May 2013 High-sensitivity high-resolution refractometry with twin turn-around-point long-period gratings in a photonic crystal fiber
Author Affiliations +
Abstract
We present the numerical design of a turn-around-point long-period grating in a photonic crystal fiber (TAP PCFLPG) for high-sensitivity, high-resolution refractometry of gases. High refractive-index sensitivity is achieved by operating LPGs in the vicinity of the dispersion turning point of the optimized PCF. Despite the resonant wavelength of the optimized PCF-LPG is highly sensitive to the refractive index of analytes, its large shifts could be monitored with a reduced resolution because the resonance dip in the TAP LPG transmission spectrum is broad. To provide also high refractive-index resolution, twin TAP-LPGs have been proposed to be used as 3 dB broadband mode converters in the interferometric scheme. The first LPG couples a portion of the light in the core mode to a forward propagating cladding mode and the second LPG couples the light back to the core mode. The resulting interference fringes within the envelope of LPG attenuation dip provide a means for higher resolution sensing. Instead of monitoring the wavelength shift as a result of a refractive index change, the transmission spectrum can also be analyzed in terms of the shift in phase suffered by the fringe pattern. This is a more accurate way of interpreting the interferometric sensor measurements, since the phase shift is a direct result of an analyte-induced change in optical path length.
© (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jiri Kanka, "High-sensitivity high-resolution refractometry with twin turn-around-point long-period gratings in a photonic crystal fiber", Proc. SPIE 8775, Micro-structured and Specialty Optical Fibres II, 87750Q (3 May 2013); doi: 10.1117/12.2017335; https://doi.org/10.1117/12.2017335
PROCEEDINGS
9 PAGES


SHARE
Back to Top