Lithographically defined nanostructures may enable the production of tuned infrared "sensorchips" for gas analysis, say researchers from Ion Optics Inc. of Waltham, Mass., and NASA's Jet Propulsion Laboratory in Pasadena, Calif. The team reported enhanced emissivity in the 5- to 11-µm range, with peak linewidth directly related to the dimensions of the surface features. The researchers etched a silicon wafer with eight crossed-dipole, quasiphotonic bandgap structures of various feature sizes and depths. They found that the structures produce a half-width comparable to that of infrared LEDs used in gas sensors, but the energy in the peak band is orders of magnitude larger.