Graphene-based adaptive liquid-crystal microlens array for a wide infrared spectral region

Abstract

An infrared liquid-crystal microlens array (IR-LCMLA) is fabricated using an isothiocyanato nematic liquid crystal (NCSNLC) material sandwiched between graphene and aluminum electrodes without alignment layers; its focus is electrically tunable in a wide infrared region. The infrared microbeam diffraction crosstalk introduced by alignment layers in previous IR-LCMLAs with the same NCSNLC is eliminated. The graded-index lens effect is achieved using a spatially nonuniform electric field generated by a microhole array electrode and a high-birefringence NCSNLC thin film at wavelengths of ~0.9 to ~11 μm. The IR-LCMLA is tuned by applying an external voltage signal; it acts as a phase retarder when the RMS voltage is below a threshold, and the tunable microlenses when the RMS voltage further increases. The proposed IR-LCMLA is an attractive candidate for infrared sensors utilizing arrayed microflux shaped and adjusted by the IR-LCMLA coupled or even integrated with them, infrared microbeam interconnection and switching, adaptive imaging based on wavefront measurement and correction, or other advanced adaptive optics applications.