Phototunable photonic crystals with reversible wavelength choice

We report a phototunable photonic crystal device whose reflection at the stop band position can be switched between valley and peak. The device is comprised of a colloidal crystal film, a photoresponsible polymer-dispersed liquid crystal film, and a holophote. The reflection spectrum of the device can be reversibly switched by ultraviolet and visible light irradiations. It was demonstrated that this device is not only used for the application of wavelength selection but is also useful for applications such as display. (C) 2007 American Institute of Physics.