Fig. 2
Broadband device images. a Overview optical micrograph image of the device. The input waveguide is first split into two waveguides, one to feed photons to the spectrometer, the other used for power calibration and monitoring the return power during the fiber-to-chip alignment. At the ends of the impedance tapers, the microstrip lines are converted to coplanar waveguides (CPWs) to match the modes of ground-signal-ground (GSG) RF probes. The yellow color represents Al and AlOx beneath, while the signal pads in orange color are made of gold (Au). Scale bar, 250 µm. b Close-up SEM image of the impedance taper. Both ends of the nanowire detector are tapered from 60 nm to microns width to preserve the fast-rising edges of photon-excited microwave pulses. Scale bar, 10 µm. c Close-up SEM image of the meander nanowire detector. The nanowire is patterned from 8 nm-thick NbN film. The width, pitch and depth of the nanowire is 60 nm, 700 nm and 3 µm, respectively. Scale bar, 1. d Angular SEM view of a section of the echelle grating. The pitch of the grating teeth is 0.8 µm and the blaze angle is 20 degree. Scale bar, 1 µm. e Expanded SEM view of the waveguide splitter. Scale bar, 10 µm. The SEM images are taken prior to the deposition of AlOx and Al for Device B (see Supplementary Note 1)
