Comparative Study of Refractive Index Sensing Based on Three Different Long-Period Grating Configurations by Pulsed ArF Excimer Laser

Using a pulsed 193-nm 10-Hz ArF excimer laser with the amplitude mask technique, we report a comparative study of sensing capabilities (refractive index and chemical solution) for three different long-period grating configurations written in a Furukawa single mode fiber. The three gratings investigated in this work were a typical long-period grating, a phase-shifted long-period grating, and a long-period grating written in a biconical tapered fiber. The principle of operation is based on the measurement of resonant wavelength shift through the change of refractive index of medium surrounding the cladding surface of the gratings. Previous studies of the three different gratings were conducted by using different fabrication methods (point-to-point writing), irradiation sources (electric-arc discharges, frequency doubled argon ion laser, and CO2 laser) and fiber types. The amplitude mask technique with a 193-nm ArF excimer laser has successfully been produced the three different long-period grating configurations and yielded comparable sensing performance with high sensitivity. Experimental results demonstrated that these fiber grating sensors could provide a resolution of similar to 10(-3) to 10(-4) for refractive indices in the range of 1.34 to 1.41, suggesting that these sensors are attractive for chemical sensing and RI measurements with aqueous solutions.