Origin of absorption enhancement in a tungsten, three-dimensional photonic crystal

A three-dimensional, metallic photonic crystal is realized and its absorption measured at infrared wavelengths. The metallic absorption rate is found to be suppressed in the photonic bandgap regime (lambda similar to 8-20 mum). On the other hand, order-of-magnitude absorption enhancement is observed at the photonic band edge (lambda similar to 5.8 mum). The enhancement is attributed to the slower group velocity of light at the photonic band edge, a longer photon-matter interaction length, and a finite intrinsic absorption of tungsten. (C) 2003 Optical Society of America.