Studies on NMR-signal up-conversion from radio-frequency to optical regimes using a lightweight nanomembrane transducer.

Our recent report on Electro-Mechano-Optical (EMO) NMR proved the feasibility of up-conversion of NMR signals from radio-frequency to optical regimes using a metal-coated, high-Q membrane oscillator (Takeda et al., 2018). However, the signal-to-noise ratio, which can in principle exceed that of the conventional electrical detection scheme, was far below than ideal. Here, we developed an aluminum-coated membrane oscillator and used for a capacitor electrode as well as a mirror of an optical cavity. Compared to the gold-deposited membrane used in our previous study, the characteristic frequency of membrane oscillation was significantly higher due to mass reduction, leading to remarkable elimination of noise in the process of conversion of radio-frequency signals to the mechanical oscillation of the membrane. Taking advantage of the significantly improved EMO NMR, we explore physics behind it in terms of coherent transduction of electrical nuclear induction signals to mechanical and then to optical signals. In addition, we study the transient response of the membrane oscillator to electrical excitation due to nuclear induction.