Experimental demonstration of optical energy transfer between the 0th and -1st orders diffracted by an all-dielectric resonant waveguide grating

The energy transfer between the reflected 0th and -1st orders diffracted by a grating in the vicinity of the Littrow angle is experimentally demonstrated for the first time with an all-dielectric resonant waveguide grating under TE polarization. This effect has already been described in a theoretical approach but never proved by measurements. Contrary to classical configuration, the dielectric resonant diffractive structure is probed here from the grating backside to avoid signal disturbance. A transparent layer of very high refractive index (hydrogenated amorphous silicon: a-Si:H) is structured by e-beam lithography and plasma etching to create a resonant grating waveguide on a BK7 substrate. Agreement between modeling and experimental characterizations validates the energy transfer effect, opening the way to all-dielectric sensing devices.