Ion beam synthesis of nanothermochromic diffraction gratings with giant switching contrast at telecom wavelengths

Nanothermochromic diffraction gratings based on the metal-insulator transition of $\mathrm{V}{\mathrm{O}}_2$ are fabricated by site-selective ion beam implantation in a $\mathrm{S}\mathrm{i}{\mathrm{O}}_2$ matrix. Gratings were defined either (i) directly by spatially selective ion beam synthesis or (ii) by site-selective deactivation of the phase transition by ion beam induced defects. The strongest increase of the diffracted light intensities was observed at a wavelength of 1550,nm exceeding a factor of 20 for the selectively deactivated gratings. The observed pronounced thermal hysteresis extending down close to room temperature makes this system ideally suited for optical memory applications.