Tunable photonic crystals on a freestanding polymer membrane

Two- and three-dimensional polymer photonic crystal structures are fabricated by multi-beam interference lithography. The cross-linked photonic crystal structures are obtained on a freestanding P(MMA-5% MaBP) membrane by combining with the standard silicon process. The resulting photonic crystal structures swell in response to the sorption of acetone solvent in the surrounding atmosphere. The optical effect of the swelling process is characterized by dynamic diffraction experiments. The results indicate that controlled polymer swelling may be used to tune the period (as well as the thickness, and thus efficiency) of the polymer-based photonic crystal structures on freestanding membranes.