Diffraction-distortion-induced deflection of guided waves in two-dimensional Ag/SiO2 nanocomposite grating coupler

摘要

Two-dimensional Ag/SiO2 nanocomposite grating coupler with a periodicity of 600 nm was fabricated by etching an Ag-ion-implanted SiO2 waveguide slab, which was evidenced to be able to convert a vertically incident beam in the wavelength range of 620-880 nm into four beams of guided waves without regard for the polarization of incident beam. Employing this coupler, the deflection of guided waves due to the diffraction distortion in the case of oblique incidence was clearly demonstrated. Moreover, to accurately predict the propagating direction of guided wave in the SiO2 waveguide layer, a simple relation of the deflected angle of guided wave to the polar and azimuth angles of incident beam was deduced according to the oblique coupling of a one-dimensional Ag/SiO2 nanocomposite grating coupler. The calculated results by using the deduced relation revealed that increasing the polar angle and/or azimuth angle of incident beam could lead to an increase in deflected angle of guided wave. Especially, for an azimuth angle of 90 degrees, the calculated results agreed well with the experimental data, justifying the deduced relation. The above findings might be useful for the packaging and applications of grating couplers.