Ultra-low-noise microwave to optics conversion in gallium phosphide

• Published in: Nature communications Vol. 13; no. 1; p. 6583
• Main Authors: Stockill, Robert, Forsch, Moritz, Hijazi, Frederick, Beaudoin, Grégoire, Pantzas, Konstantinos, Sagnes, Isabelle, Braive, Rémy, Gröblacher, Simon
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 03-11-2022; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/483; 639/925/927; Actuation; Gallium; Gallium arsenide; Gallium phosphides; High impedance; Humanities and Social Sciences; Impedance matching; Mechanical properties; Microwave radiation; multidisciplinary; Optical radiation; Optics; Photon absorption; Photons; Piezoelectricity; Resonators; Science; Science (multidisciplinary); Thermal noise; Thin films
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-34338-x

Mechanical resonators can act as excellent intermediaries to interface single photons in the microwave and optical domains due to their high quality factors. Nevertheless, the optical pump required to overcome the large energy difference between the frequencies can add significant noise to the transduced signal. Here we exploit the remarkable properties of thin-film gallium phosphide to demonstrate bi-directional on-chip conversion between microwave and optical frequencies, realized by piezoelectric actuation of a Gigahertz-frequency optomechanical resonator. The large optomechanical coupling and the suppression of two-photon absorption in the material allows us to operate the device at optomechanical cooperativities greatly exceeding one. Alternatively, when using a pulsed upconversion pump, we demonstrate that we induce less than one thermal noise phonon. We include a high-impedance on-chip matching resonator to mediate the mechanical load with the 50-Ω source. Our results establish gallium phosphide as a versatile platform for ultra-low-noise conversion of photons between microwave and optical frequencies.
Coherently interfacing microwave and optical radiation at the single photon level is an outstanding challenge in quantum technologies. Here, the authors show bi-directional on-chip conversion between MW and optical frequencies exploiting piezoelectric actuation of a gallium phosphide optomechanical resonator.