Fig. 3: Pulsed microwave-optical photon conversion.
From: Cavity piezo-mechanics for superconducting-nanophotonic quantum interface
a A schematic of measurement scheme with pulsed optical pump. A 3-μs-wide red-detuned pump pulse is generated by on/off switching using an acoustic-optic modulator (AOM). To characterize the device temporal response, a low-frequency microwave signal (δ0 = 40 MHz) from a lock-in amplifier (not shown here) is upconverted to f ~ 10 GHz around the mechanical resonance by single-sideband (SSB) modulation. The signal is then sent to the device either as the microwave input (switch pos. 1), or the optical input after the optical SSB generation (pos. 2). The microwave or optical output (pos. 3 and 4, respectively) is then downconverted to 40 MHz and sent to the lock-in amplifier to measure the quadratures in time domain. PD: photodetector, LNA: low-noise RF amplifier. b Theoretical calculation of the temporal response of the system under a pulsed pump (profile indicated in gray dashed line in the top panel). ncav: intra-cavity photon number. Soe and Seo: microwave-to-optical and optical-to-microwave conversion signal, respectively. c Experimental data of the pulsed conversion signals at different input detunings from the mechanical resonance (\(\frac{{\omega }_{{\rm{m}}}}{2\pi }=10.220\ {\rm{GHz}}\)). The measurement time resolution is Δt ≈ 1.17 μs. d, e Coherent bidirectional microwave-optical photon conversion spectra with both amplitude and phase responses.
