Photonic Crystal Shifts Energy

Photonic crystals are artificial structures, sometimes consisting of stacked rods, or arrays of holes bored into a solid, which permit light in some wavelength bands to pass through while rejecting light at other bands.

New work at Sandia National Lab indicates that a photonic crystal made from half-micron-diameter tungsten rods, excited by thermal heating, suppresses light at longer wavelengths and re-emits light at a shorter wavelength band, one that may be more useful for such technological applications as photovoltaic power generation, or building a better lightbulb.

Shawn Lin and his Sandia colleagues, in the course of their studies of photonic crystals, have seemed to challenge the venerable formulation, made by Max Planck a hundred years ago, of what kind of emission spectrum a body should have. The Sandia photonic crystal seems to emit between 4 and 10 times as much radiation in the near infrared than a body at that temperature (the sample had been heated to 1250 C) should be emitting. (Lin et al., Applied Physics Letters, 14 July 2003; Lin et al., Optics Letters, Sep.15, 2003.)