High‐Power Continuous‐Wave Optical Waveguiding in a Semiconductor Nanowire

Semiconductor nanowires have been extensively studied for a wide range of nanophotonic applications, including nanolasers, photodetectors, nonlinear frequency converters, and solar cells. While high‐power optical waveguiding is often desired in these applications, the guided power (or average power) in individual nanowires has so far been typically limited to about 100 μW due to propagation losses and low‐efficiency optical coupling. Here, we demonstrate high‐power continuous‐wave (CW) optical waveguiding in CdS and ZnO nanowires enabled by efficient in‐ and out‐coupling using silica fiber tapers. A single 550‐nm‐diameter CdS nanowire at 1550‐nm wavelength is shown to safely guide optical power up to 2.5 W, which is approximately four orders of magnitude higher than previous results. Using these high‐power CW optical waveguiding nanowires, we further realize efficient nonlinear frequency conversion with second‐ and third‐harmonic generation efficiencies of 6.9 × 10 −6 and 6.4 × 10 −8 , respectively, comparable to those obtained under pulsed excitation. These results may push nanowire photonics into the high‐power regime and open up new opportunities for both fundamental studies and technological applications.