Metamaterial saturable absorber mirror

We propose a metamaterial saturable absorber mirror at midinfrared wavelengths that can show a saturation of absorption with intensity of incident light and switch to a reflecting state. The design consists of an array of circular metallic disks separated by a thin film of vanadium dioxide (VO2) from a continuous metallic film. The heating due to the absorption in the absorptive state causes the VO2 to transit to a metallic phase from the low temperature insulating phase. The metamaterial switches from an absorptive state (R similar or equal to 0.1%) to a reflective state (R > 95%) for a specific threshold intensity of the incident radiation corresponding to the phase transition of VO2, resulting in the saturation of absorption in the metamaterial. The computer simulations show over 99.9% peak absorbance, a resonant bandwidth of about 0.8 mu m at 10.22 mu m wavelengths, and saturation intensity of 140 mW cm(-2) for undoped VO2 at room temperature. We also carried out numerical simulations to investigate the effects of localized heating and temperature distribution by solving the heat diffusion problem. (C) 2013 Optical Society of America