Superconducting Acousto-optic Phase Modulator

• Published in: arXiv.org 2021-04
• Main Authors: Okada, Ayato, Yamazaki, Rekishu, Fuwa, Maria, Noguchi, Atsushi, Yamaguchi, Yuya, Kanno, Atsushi, Yamamoto, Naokatsu, Hishida, Yuji, Terai, Hirotaka, Tabuchi, Yutaka, Usami, Koji, Nakamura, Yasunobu
• Format: Article
• Language: English
• Subjects: Acousto-optics; Cryogenic temperature; Lithium niobates; Modulation; Modulators; Niobium; Optical waveguides; Optics; Performance evaluation; Substrates; Superconductivity; Surface acoustic wave devices; Thin films; Titanium nitride
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2104.11508

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