Superconducting acousto-optic phase modulator

We report the development of a superconducting acousto-optic phase modulator fabricated on lithium niobate substrate. A titanium-diffused optical waveguide is placed in surface acoustic wave resonator, where electrodes for mirrors and an interdigitated transducer are made niobium titanium nitride thin film. The device performance evaluated as substitute current electro-optic modulators, with same fiber coupling scheme comparable size. Operating at cryogenic temperature (T=8K), we observe length-half-wave-voltage (length-$V_\pi$) product 1.78 V$\cdot$cm. Numerical simulation conducted to reproduce extrapolate device. An cavity mirror coating input/output facets tested further enhancement modulation efficiency. simple extension estimated achieve efficient $V_\pi=$ 0.27 V.