Fig. 3. Propagation of the on-resonant monochromatic lights.

a Propagation directions of the resonant light after being coupled into the waveguide. Results show that the resonant light will propagate perpendicularly with respect to the longitudinal direction of the grating strips in the in-plane direction. Arrows denote the propagation direction. b Field distribution in the waveguide with different monochromatic lights. Results show that different resonant lights can be effectively confined within the combined waveguide. c Light propagation at the perovskite-waveguide interface. Due to the large n of perovskites, resonant light propagating through the waveguide will further transport into the perovskite layer for an optoelectronic signal