Design of turn-around-point long-period gratings in a photonic crystal fiber for refractometry of gases

0396714 - ÚFE 2014 RIV CH eng J - Journal Article
Kaňka, Jiří
Design of turn-around-point long-period gratings in a photonic crystal fiber for refractometry of gases.
Sensors and Actuators B - Chemical. Roč. 182, č. 6 (2013), s. 16-24. E-ISSN 0925-4005
R&D Projects: GA MŠMT(CZ) LD11030; GA MŠMT(CZ) LF11001
Institutional support: RVO:67985882
Keywords : Fiber design * Photonic crystal fiber * Microstructured optical fiber
Subject RIV: BH - Optics, Masers, Lasers
Impact factor: 3.840, year: 2013

A fiber-optic long-period grating (LPG) operating near the dispersion turning point in its phase matching curve, referred to as a turn-around-point (TAP) LPG, is known to be highly sensitive to external parameters. So far TAP LPGs have been realized in specially designed or post-processed conventional fibers, not yet in PCFs, which allow a great degree of freedom in engineering the fiber's dispersion properties through the control of the PCF structural parameters. We have developed the design optimization technique for TAP PCF-LPGs employing the finite element method for PCF modal analysis in a combination with the Nelder-Mead simplex method for minimizing the objective function based on target-specific PCF properties. Using this tool TAP PCF-LPGs can be designed for specified wavelength ranges and refractive indices of medium in the air holes. We present here the dispersion optimization of PCF-LPG for refractometry of gases. The resonant wavelength of an optimized PCF-LPG is subsequently highly sensitive to the refractive index of gaseous analytes, however, its large shifts could be detected with a substantially reduced resolution because the resonance dip in the TAP LPG transmission spectrum is broad. We have resolved the resolution problem by proposing an interferometric scheme based on twin TAP LPGs
Permanent Link: http://hdl.handle.net/11104/0224488