Deep gratings filled with liquid crystal as tunable photonic metamaterial

Subwavelength deep gratings are an excellent platform that exhibits several types of resonances depending on the wavelength-to-period ratio, the refractive index, and the depth, such as guided mode resonance (GMR), surface electromagnetic waves, bound in the continuum (BIC) states, Fano resonances, and more. When the period is much less than the wavelength, the gratings can be homogenized into a uniform negative uniaxial waveplate. In this work, we have shown that nematic LC material can be filled in between the grating lines to provide electro-optic and thermal tunability of resonances of tens of nanometers. The confinement in a resonant sub-micron region of 560nmX700nm sheds new light on the behavior of LC molecules in nanocavities and the possibilities for future improved design and manufacture of tunable metamaterial devices with improved performance.