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Pure Appl. Chem., 2000, Vol. 72, No. 1-2, pp. 309-315

Multiply coated microspheres. A platform for realizing fields-induced structural transition and photonic bandgap

Ping Sheng*, Weijia Wen, Ning Wang, Hongru Ma, Zhifang Lin, W. Y. Zhang, X. Y. Lei, Z. L. Wang, D. G. Zheng, Wing Yim Tam and C. T. Chan

Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China

Abstract: Under crossed electric and magnetic fields, multiply coated microspheres form columnar crystallites with an internal structure that transforms from body-centered-tetragonal to face-centered-cubic as the ratio between the magnetic and the electric fields exceeds a minimum value. The observed transition scenario is in excellent agreement with calculations. These multiply coated microspheres also serve as building blocks for photonic crystals. Robust photonic gaps exist in any periodic structure built from such spheres when the filling ratio of the spheres exceeds a threshold.