Tunable liquid crystal-resonant grating filters using superimposed grating structures fabricated by nanoimprint lithography

Tunable resonant grating filter with super-imposed alignment gratings for liquid crystal E7 cladding as the tuning layer was demonstrated. In the fabrication of the super-imposed gratings (SIG), the first level of 200 nm pitch gratings was imprinted in a thin layer of spun-on thermoplastic resist by thermal nanoimprint lithography, using a mold pre-fabricated by interference lithography. At a resonant wavelength incident upon the structure, a waveguide mode was excited in the waveguide layer through evanescent wave. It was observed that the potential for monolithic integration on a chip, easy fabrication, and low cost will make SRG filter an important element for wavelength division multiplexing (WDM) optical telecommunication.