Researchers at the Department of Energy's Sandia National Laboratories in Albuquerque, N.M., have created a cheesecloth-like bar that bends infrared beams with low loss. This development may provide a simple, essentially two-dimensional method for drastically reducing the energy required to start and operate a laser. Currently, a significant portion of the energy input to lasers merely compensates for the large amount of light that is ordinarily dispersed in the lasing process.
Made up of a photonic crystal with holes, this device is basically a wire for light. The size and periodic placement of the holes form a construction that blocks most light waves. At the same time, this structure transmits light waves from a selected band of wavelengths that can navigate the geography (see the figure). Since the instrument is a 2D photonic crystal, the arrangement of its holes substitutes for the spaces between molecules in real crystals. While real crystals are restricted by their prearranged molecular spacing, the spacing of the artificial crystal components can be varied to let a variety of frequencies pass.
Comprised of 200-nm holes made by electron-beam lithography, the construction resembles a narrow cross-section of a beehive with cell centers at 416 nm. The crystals, built from gallium arsenide without metallic components, has little measurable intrinsic loss or distortion as it guides infrared light around sharp corners. By capping the top of the structure with silicon oxide and the bottom with aluminum oxide, light is prevented from escaping.
The cladding provides a large difference in the index of refraction. Moreover, it enables the light to remain traveling within the central portion of gallium arsenide.
Sandia researchers have previously worked with 3D silicon photonic crystals, but these 2D formations are cheaper and easier to build. This technique may potentially replace electronic chips with faster, cooler photonic chips. It also can be used to combine light with electrons in a single chip. In addition, the direction of optical signals coming through telecommunication lines may be relayed or changed using this experimental device.
For more information on the developments at Sandia, visit www.sandia.gov.