Fig. 3
From: Flexible integration of free-standing nanowires into silicon photonics
Integration of a FNW into a silicon chip using a vertical coupling scheme. a Schematic diagram of the vertical coupling structure suspending a FNW across two SWs collinearly. The white arrow indicates the direction of light propagation. b Wavelength-dependent coupling efficiency of a 770-nm-diameter CdS FNW with a 320-nm-width SW. Inset shows an SEM image of the coupling structure with a pre-defined coupling length of about 4 μm. Scale bar, 5 μm. c SEM image of a hybrid FNW–SW racetrack resonator. A bus waveguide is used for optical signal launching and collection. The overall length of the racetrack is consisted by a 60-μm CdS FNW and a 154-μm SW. Scale bar, 10 μm. d Transmission spectrum of the hybrid resonator. e Modulated signal output by all-optical modulation when the FNW is excited by 405-nm switch pulses
