Perfectly notched long-period fiber grating filter based on ICP dry etching technique.

This study presents a new process using inductively a coupled plasma dry etching method to manufacture a long-period fiber grating filter with exact period, vertical sidewalls, and smooth etched surfaces, and the filter is thus named a perfectly notched long-period fiber grating (NLPFG). This process can dramatically reduce production time, and thereby provide higher volume production. The fabricated NLPFG has periods of 640 μm, resonant-attenuation wavelengths of 1518 nm, and maximum resonance-attenuation of 21.79 dB. A force induced loss-tunable calibration of the NLPFG filter was implemented, and a monotonically increasing quadratic fitting was observed. The results demonstrated that the proposed NLPFG has a much better period precision compared to corrugated LPFG, and it has great potential for a loss-tunable filter and force transducer applications.