High-sensitivity high-resolution refractometry with twin turn-around-point long-period gratings in a photonic crystal fiber

0396688 - ÚFE 2014 RIV US eng C - Konferenční příspěvek (zahraniční konf.)
Kaňka, Jiří
High-sensitivity high-resolution refractometry with twin turn-around-point long-period gratings in a photonic crystal fiber.
MICRO-STRUCTURED AND SPECIALTY OPTICAL FIBRES II. Vol. 8775. BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING, 2013 - (Kalli, K.; Kanka, J.; Mendez, A.). ISBN 978-0-8194-9577-8. ISSN 0277-786X.
[Conference on Micro-structured and Specialty Optical Fibres II. Prague (CZ), 15.04.2013-17.04.2013]
Grant CEP: GA MŠMT(CZ) LD11030
Institucionální podpora: RVO:67985882
Klíčová slova: fibre design * Photonic crystal fibres * interferometric sensor
Kód oboru RIV: JA - Elektronika a optoelektronika, elektrotechnika

We present the numerical design of a turn-around-point long-period grating in a photonic crystal fiber (TAP PCF-LPG) 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
Trvalý link: http://hdl.handle.net/11104/0224440