Enhancing the tuning range of a single resonant band long period grating while maintaining the resonant peak depth by using an optimized high index indium tin oxide overlay

We report laboratory test results of a long period grating (LPG) that can maintain a constant resonant peak depth over an enhanced tuning range when it is coated with an indium tin oxide (ITO) electrode that has optimized thickness and refractive index. The authors have experimentally demonstrated a LPG coated with ITO that can be tuned in excess of 200 nm with an ambient refractive index change of less than 0.01. To the best of the authors' knowledge, this is the highest sensitivity reported for a LPG to date. In addition to the tuning performance, the resonant peak remains within 1 dB of its maximum depth for at least 100 nm of the tuning range.