A new photopolymerizable material allows single-step, fast recording of
volume holograms with properties that can be electrically controlled.
Polymer-dispersed liquid crystals (PDLCs) in accordance with the
invention preferably comprise a homogeneous mixture of a nematic liquid
crystal and a multifunctional pentaacrylate monomer in combination with
photoinitiator, coinitiator and cross-linking agent. Optionally, a
surfactant such as octancic acid may also be added. The PDLC material is
exposed to coherent light to produce an interference pattern inside the
material. Photopolymerization of the new PDLC material produces a
hologram of clearly separated liquid crystal domains and cured polymer
domains. Volume transmission gratings made with the new PDLC material can
be electrically switched between nearly 100% diffraction efficiency and
nearly 0% diffraction efficiency. By increasing the frequency of the
switching voltage, switching voltages in the range of 50 Vrms can be
achieved. The optional use of a surfactant allows low switching voltages
at lower frequencies than without a surfactant. In an alternative
embodiment, a PDLC material in accordance with the invention can be
utilized to form reflection gratings, including switchable reflection
gratings. In still further embodiments, a PDLC material in accordance
with the invention can be used to form switchable subwavelength gratings.
By further processing, static transmission, reflection, and subwavelength
PDLC materials can be formed. In addition, PDLC materials in accordance
with the present invention can be used to form switchable slanted
transmission gratings suitable for switchable optical coupling and
reconfigurable optical interconnects.