Thickness dependence of the optical properties of ordered silica-air and air-polymer photonic crystals

We report observations of the optical stop band of periodic planar arrays o f submicron silica spheres, and of macroporous polymers grown from these si lica templates. The stop-band width and peak attenuation depend on the numb er of layers and on the dielectric contrast between the spheres and the int erstitial regions, both of which are experimentally controlled. The results an compared to the predictions of the scalar wave approximation. This is t he first systematic study of the thickness dependence of the stop band in c olloidal photonic band gap structures.