Electro-optic frequency shifter and beam splitter in coupled lithium niobate microring resonators

Efficient and precise control of the frequency of light on gigahertz scales is important for a wide range of applications. Here we demonstrate an on-chip electro-optic frequency shifter that is precisely controlled using only a single-tone microwave signal. Our device provides frequency shifts as high as 28 GHz with measured shift efficiencies of 99% and on-chip device insertion loss of <0.5 dB. Importantly, the device can be reconfigured as a tunable frequency-domain beam splitter. Using the device, we also demonstrate an efficient and non-blocking exchange of information between two distinct frequency channels, i.e. swap operation. Finally, we show that our scheme can be scaled to achieve cascaded frequency shifts beyond 100 GHz.