Fig. 4: Conversion noise properties. | Nature Communications

Fig. 4: Conversion noise properties.

From: Converting microwave and telecom photons with a silicon photonic nanomechanical interface

Fig. 4

Measured noise spectra at the device output for the optical cavity (a) and the microwave resonator (b) as a function of the signal tone detuning δj = ω − (ωd,j + ωm) at fixed pump powers Pe = 601 pW and Po = 625 pW in units of added noise quanta. a The dark blue region represents the two-quadrature noise added by the optical measurement chain; the light blue region indicates the thermal mechanical noise added to the converted optical output signal. b Bottom light red region represents the two-quadrature background noise from the microwave measurement chain. The central dark red region indicates a small amount of broadband resonator noise and the light blue region the transduction noise due to the thermal population of the mechanical mode. In both panels, fits to one common mechanical bath nm are shown in black. c Mechanical bath temperature Tm,bath extracted as only fit parameter from fits to the measured output noise as in (a) and (b) with respect to optical (blue dots, Pe = 601 pW) and microwave (red dots, Po = 625 ± 19 pW) pump power. Black lines show fits to the data with the logarithmic growth function \(T_{\mathrm{m,bath}}=0.18\ {\mathrm{log}\,}_{{\rm{e}}}({P}_{{\rm{o}}})-0.47\) and Tm,bath = 0.70 K respectively. The dashed line indicates the thermalized mechanical mode temperature Tsample when both pumps are off. d Microwave (red, nadd,e) and optical (blue, nadd,o) added noise photons at the output with respect to optical pump power (Pe = 601 pW). The full theory based on an interpolation of Tm,bath from (c) is shown as black lines.

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