Characterization of liquid crystals impregnated micrometric diffraction gratings for an active near-IR light extraction control

Due to their narrow reflection peak as well as their compact structure, guided mode resonance filters (GMRFs) are attractive for many applications. In this work, we will demonstrate the possibility to modulate the properties of a GMRF by associating it with liquid crystals (LCs). By impregnating the diffraction grating with LCs, it is possible to switch between an active and an inactive state depending on the polarization of the light or the applied voltage. In this paper we fabricated and characterized the first diffraction order of LC-impregnated gratings with different periods (0.8–5.0 µm) and depths (120 and 840 nm) to test the ability of liquid crystals to adjust the diffraction properties. Finally, without voltage, more than 99.8% of initial diffraction could be turned off with a 90° rotation polarization whereas, by applying a voltage of 30 V; 90–99% of the initial diffraction is turned off according to the grating dimensions. The effect of the grating dimension (period, depth) on the diffraction modulation capacity will be discussed.