Steering of second-harmonic emission by the mode-selective excitation in a hybrid waveguide

Realization of the efficient steering for photons streams from nano sources is essential for further progress in integrated photonic circuits, especially when involving nonlinear sources. In general, steering for nonlinear sources needs additional optical control elements, limiting their application occasions as photonic devices. Here, we propose a simple and efficient beam steering scheme for the second-harmonic (SH) emission in the hybrid waveguide (consisting of CdSe nanobelts on the Au film) by mode-selective excitation. Adjusting the position of the incident beam illuminating on the tapered waveguide, the excitation types of guided modes can be selected, realizing the directionality control of SH emission. Stable steering of 6.1° for the SH emission is observed when the interference modes change from TE 00 & TE 01 to TE 00 & TE 02 , which is confirmed by SH Fourier imaging and simulations. Our approach gets rid of the complex structural design and provides a new idea for beam steering of nonlinear optical devices with various nonlinear wavefronts.