Three-dimensional photonic-crystal emission through thermal excitation

A three-dimensional tungsten photonic crystal is thermally excited and shown to emit light at a narrow band, $\lambda =3.3–4.25 \mathit{\mu }\mathrm{m}$. The emission is experimentally observed to exceed that of the free-space Planck radiation over a wide temperature range, $T=475–850 \mathrm{K}$. It is proposed that an enhanced density of state associated with the propagating electromagnetic Bloch waves in the photonic crystal is responsible for this experimental finding.