COUPLING BETWEEN TWO PARALLEL LONG-PERIOD FIBER GRATINGS WRITTEN BY HIGH-FREQUENCY CO2-LASER PULSES

摘要

We demonstrate light coupling between two parallel LPFGs written by high-frequency CO2-laser pulses. We show that the coupling efficiency depends strongly on the axial orientations of the two gratings. When the two gratings are aligned in such a way that the sides exposed to the CO2-laser pulses face each other, the coupling efficiency is maximized. Using two almost identical 33-mm long gratings, we achieve a maximum coupling efficiency of ～15% at the resonance wavelength by applying a suitable index-matching liquid to the interaction section of the fibers.