All-Optical Controlling Waveguide Grating Filter Using Ionic-Gel Polymer Electrolyte Based on Photothermal Effect

In this work, all-optical controlling Bragg grating filter with loading waveguide structure was prepared based on photothermal effect of the ionic-gel polymer electrolyte (polymeric ionic liquid (PIL) and polybenzimidazole (PBI) composite, PIL/PBI). The thermo-optic coefficient of PIL/PBI from free ionic concentration changing is $\sim 10^{-{3}}$ /K. The performances of the Bragg grating filter by thermo-optic tuning are simulated. The photothermal coefficient of PIL/PBI uploading waveguide is obtained as 5.7 K/mW. The actual sensitivity of the grating filter is obtained as 29.2 nm/mW. In the future, an ultra-compact all-optical filter might be accomplished using this method.