Non-reciprocal optical frequency shifter and polarization rotator on chip

Optical light has exhibited versatile degree of freedoms, such as frequency and polarization, that can be used for encoding information in optical quantum computing. However, controlling these degree of freedoms in integrated photonic platform has been challenging. In this work, we demonstrated a frequency domain beam-splitter, which is the building block for frequency encoded qubit in high dimensional quantum computing. By spatio-temporally modulating an optical ring resonator via three Aluminum Nitride bulk acoustic wave resonators, a pair of transverse electrical (TE) and transverse magnetic (TM) optical modes are strongly coupled. The output light shifts in both frequency and polarization, with conversion efficiency (beam splitting ratio) controlled by microwave power. Maximum of 50% energy conversion is achieved, with 15 dB suppression of carrier frequency and 12 dB sideband asymmetry. The indirect interband transition breaks the spatial reciprocity, where the conversion only happens when light inputs in phase matched direction.