Faraday effect of photonic crystals

We measured Faraday rotation in three-dimensional photonic colloidal crystals impregnated with a Faraday active, transparent liquid. The Faraday effect was found to strongly increase inside the stop band, whereas outside it follows the normal spectral behavior of a paramagnetic dielectric with an effective Verdet constant equal to the product of the liquid’s Verdet constant and its filling fraction.