A photonic band gap crystal produced by a colloidal crystallization technique using sized, template spheres.

Not long ago, theory and experiments failed to agree on the question of how light propagates in crystals. But in 1990, researchers at Ames Laboratory proved the theorists correct by demonstrating the existence of structures with a "photonic bandgap" (PBG), a range of frequencies within which a specific wavelength of light is blocked. Scientists then knew they could custom-design crystals to trap and manipulate light, sending it down assigned routes and even around loops and bends. Among their novel optical properties, PBG crystals can manipulate light without absorption; the energy not emitted in one frequency region is redirected into other frequencies, a useful feature in energy-efficient devices. Early photonic crystals had a bandgap in the microwave region of the electromagnetic spectrum. Using a layered lattice design and microfabrication capabilities at Sandia National Laboratories, scientists moved the bandgap to shorter wavelengths, in the infrared, for applications such as optical communications. Ames also produced computer programs that allow for the rapid design, analysis, and optimization of PBG structures.

Scientific Impact: The Ames' work spawned a growing global research community and knowledge base focusing on PBG crystals and related atomic properties and behavior. The high accuracy of Ames? theoretical calculations assists in the interpretation and design of PBG experiments and devices, and the layered lattice approach has been used to make the smallest PBG crystal ever fabricated.

Social Impact: PBG crystals could revolutionize the control of light propagation, emission, and absorption in optical devices; thus, they have many potential uses in compact and efficient sensors, antennas, lasers, electronics, lighting, solar cells, and telecommunications equipment (e.g., optical switches, waveguides). The microfabrication method developed at Sandia is economical and lends itself to mass production.

Reference: "Photonic Crystals," M.M. Sigalas, R. Biswas, G. Tuttle, C.M. Soukoulis, and K.M. Ho, Wiley Encyclopedia of Electrical and Electronic Engineering, Volume 16, 345 (John Wiley, 1999).

"Existence of a photonic gap in periodic dielectric structures," K. M. Ho, C. T. Chan, and C. M. Soukoulis, Phys. Rev. Lett. 65, 3152 (1990).

URL: http://www.public.iastate.edu/~cmpexp/groups/ho/pbg.html
http://www.mdl.sandia.gov/photonics/newsnote1.html

Technical Contact: Don Freeburn, Office of Basic Energy Sciences, 301-903-3156

Press Contact: Jeff Sherwood, DOE Office of Public Affairs, 202-586-5806

SC-Funding Office: Office of Basic Energy Sciences