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 (λ∼8–20 μm). On the other hand, order-of-magnitude absorption enhancement is observed at the photonic band edge (λ∼5.8 μm). 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.