Guided-mode resonant wave plates

We introduce half-wave and quarter-wave retarders based on the dispersion properties of guided-mode resonance elements. We design the wave plates using numerical electromagnetic models joined with the particle swarm optimization method. The wave plates operate in reflection. We provide computed results for reflectance and phase in the telecommunication spectral region near 1: 55 mu m wavelength. A surface-relief grating etched in glass and over-coated with silicon yields a half-wave plate with nearly equal amplitudes of the TE and TM polarization components and pi phase difference across a bandwidth exceeding 50 nm. Wider operational bandwidths are obtainable with more complex designs involving glass substrates and mixed silicon/hafnium dioxide resonant gratings. The results indicate a potential new approach to fashion optical retarders. (C) 2010 Optical Society of America