Researchers from Brown University in Providence, R.I., have fabricated two- and three-dimensional tunable photonic crystals using polymer-dispersed liquid crystal. They presented the results of their study at the 2003 Optical Fiber Communication conference and exposition in Atlanta in March.To create the photonic crystals, the scientists sandwiched photosensitive monomer, photo-initiator and nematic liquid crystal between substrates coated with a transparent electrode. To generate the desired interference patterns, they exposed the mixture to four beams of 532-nm light from a diode-pumped Nd:YAG laser, using four half-wave plates to control the polarization and two 90° prisms to control the angle of propagation within the film.