Fig. 1: Silicon photonic microwave-to-optics converter. | Nature Communications

Fig. 1: Silicon photonic microwave-to-optics converter.

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

Fig. 1

a Diagram showing the microwave \(({\hat{a}}_{{\rm{e}}})\), mechanical \((\hat{b})\), and optical \(({\hat{a}}_{{\rm{o}}})\) mode, and the relevant coupling and loss rates of the device. Scattering parameters Sij characterizing the transducer performance are indicated. b Schematic showing the frequencies of the coherent signals involved in the conversion process (green arrows). On the left an optical input signal (IS) is converted to an upper sideband (US) of the microwave pump signal, whereas in the microwave-to-optics conversion on the right also the lower sideband (LS) is created. The bidirectional transduction ζ is only evaluated between the upper sidebands at ωd,j + ωm. c Scanning electron micrograph of the device showing the microwave lumped element resonator with an inductively coupled feed line, the photonic crystal cavity, and the optical coupling waveguide fabricated on a fully suspended 220 nm thick silicon-on-insulator device layer. White scale bar, 10 μm. The inset shows an enlarged view of the central part (green boxed area) comprising the mechanically compliant vacuum gap capacitors of size  ~70 nm and two optomechancial zipper cavities (top one unused) with a central tapered photonic crystal mirror coupled optical waveguide. White scale bar, 1 μm. d Finite-element method (FEM) simulation of the mechanical displacement u of the utilized mechanical resonance. e FEM simulation of the electric in-plane-field Ey(xy) for the relevant optical mode. f Simplified experimental setup. The device is mounted on the mixing chamber plate of a cryogen-free dilution refrigerator at a temperature of Tfridge = 50 mK. A microwave switch selects between the incoming microwave and optical signal to be analyzed by the ESA. Optical heterodyning is used to detect the low power levels used in the experiment. SG microwave signal generator; ESA electronic spectrum analyzer; VOA variable optical attenuator; SSB EOM single-sideband electro-optic modulator; AOM acousto-optic modulator.

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