B. N. Harmon, M. M. Sigalas, R. Biswas, K. M. Ho, C. M. Soukoulis, G. Subramania,
I. El-Kady, B. Vasiliu, and D. E. Turner,
Iowa State University/Ames Laboratory
S. Y. Lin, Sandia National Laboratories, New Mexico

Research Objectives

This research project has two thrusts: (1) The design and development of novel structures and photonic devices in the infrared and optical regimes with full three-dimensional band gaps. These include unusual colloidal crystals being fabricated by our collaborators at Ames Laboratory, for photonic gaps at optical wavelengths. (2) Development of applications in the microwave and millimeter wave regime for existing 3D photonic band gap (PBG) crystals, especially those fabricated at Ames Laboratory. These include novel waveguides that can bend electromagnetic waves with bending radii of the order of a single wavelength.

Computational Approach

The Transfer Matrix Method (TMM) is used to design and study PBG filters. Maxwell's equations are solved to determine the reflection and transmission of electromagnetic waves from a finite thickness PBG material. The method can incorporate realistic absorption- and frequency-dependent dielectric functions. The TMM code has been run on a variety of MPP systems including the Intel Paragon and Cray T3E. Added power and memory will enable us to study disordered systems and defect states in large cavities.

These figures are snapshots of the electromagnetic fields in two adjacent layers in a periodic dielectric system. Defects have been introduced so that the electromagnetic waves propagate around a corner, producing a waveguide with near perfect efficiency.

In the Finite Difference Time Domain (FDTD) method, Maxwell's equations are discretized on a real-space grid. The time evolution of the electromagnetic fields is calculated by solving the time-dependent Maxwell's equations. This code can simulate the radiation properties of antennas or the bending of light in a photonic crystal. A parallel version of this code has been developed for the Intel Paragon and workstation clusters. Some simple optimizations will allow it to run efficiently on the Cray T3E, where larger and more realistic systems can be simulated.

Accomplishments

We have designed new photonic lattices, fabricated at Sandia National Laboratories, that can for the first time manipulate 1.5 micron wavelengths used for optical fibers. In joint work with the Sandia group, we designed an ultra-small optical cavity, with dimensions smaller than the wavelength of light. This single mode cavity has been fabricated at Sandia and is likely to be the smallest cavity ever at infrared wavelengths. We have utilized our FDTD method to calculate radiation patterns of antennas on and inside PBG crystals. We have found optimal configurations with improved radiation patterns that cannot be achieved by conventional materials.

Significance

PBG structures have immense potential to develop novel materials and devices with desired electromagnetic signatures. Applications include suppression of optical radiation modes, higher-efficiency lasers, and new microwave and millimeter wave devices. The computational design of PBG structures has always been the first step in developing new photonic crystals. Computational simulation can rapidly test the electromagnetic behavior of new structures and then select the best-performing ones for fabrication. This research will open up new ways to manipulate light within these PBG structures, including the bending of light by waveguides and the ability to control emission of light within microcavities. These capabilities are essential in developing photonic devices that promise to be much faster than present-day electronic devices.

Publications

S. Y. Lin, J. Fleming, R. Biswas, M. M. Sigalas, K. M. Ho, B. K. Smith, D. L. Hetherington, W. Zubrzycki, S. R. Kurtz, and J. Bur, "A three dimensional photonic crystal in the infrared wavelengths," Nature 394, 251 (1998).

S. Lin, J. Fleming, M. M. Sigalas, R. Biswas, and K.-M. Ho, "Photonic band gap microcavities in three dimensions," Phys. Rev. B 59, 15579 (1999).

G. Subramania, K. Constant, R. Biswas, M. M. Sigalas, and K.-M. Ho, "Optical photonic crystals fabricated from colloidal systems," Appl. Phys. Lett. 74, 3933 (1999).