Reconfigurable optical filter

A narrowband, widely tunable optical filter with a reconfigurable spectrum is proposed, and the critical component for the filter operation is demonstrated. The filter is based on a whispering gallery mode resonator made of domain engineered LiNbO3 crystal. The main feature of the filter is tunability of the spacing between some of the optical modes of the resonator. The spacing is electro-optically manipulated at 7 GHz in the linear regime with approximately 21 MHz/V tuning rate. The filter operates at 1.55 µm wavelength, and is characterised with 10 MHz bandwidth, 5 dB fibre-to-fibre insertion loss and 20 ns tuning speed.