Rongtang Fu

Coloration strategies in peacock feathers

We report the mechanism of color production in peacock feathers. We find that the cortex in differently colored barbules, which contains a 2D photonic-crystal structure, is responsible for coloration. Simulations reveal that the photonic-crystal structure possesses a partial photonic bandgap along the direction normal to the cortex surface, for frequencies within which light is strongly reflected. Coloration strategies in peacock feathers are very ingenious and simple: controlling the lattice constant and the number of periods in the photonic-crystal structure. Varying the lattice constant produces diversified colors. The reduction of the number of periods brings additional colors, causing mixed coloration.

Absorption in one-dimensional metallic–dielectric photonic crystals

We show theoretically that the absorption of one-dimensional metallic–dielectric photonic crystals can be enhanced considerably over the corresponding constituent metal. By properly choosing the structural and material parameters, the absorption of one-dimensional metallic–dielectric photonic crystals can be enhanced by one order of magnitude in the visible and in the near infrared regions. It is found that the absorptance of such photonic crystals increases with increasing number of periods. Rules on how to obtain a absorption enhancement in a certain frequency range are discussed.

Tunability of photonic crystals based on the Faraday effect

We show theoretically that the photonic band structures of photonic crystals (PhCs) with constituent materials containing free carriers can be tuned by an external magnetic field in the frequency range below the far infrared region. We take one-dimensional PhCs consisting of an intrinsic InSb layer and an air layer stacked alternately as an example in studying photonic band structures and transmissive properties within the magnetic field.

Effects of Disorder on Group Velocity in One-Dimensional Photonic Crystals

Effects of thickness disorder on the superluminal group velocity within photonic band gaps and the ultralow group velocity of defect modes in one-dimensional photonic crystals are studied theoretically. It is found that the introduction of thickness disorder leads to a decrement in group velocity of the superluminal modes and an increase in group velocity of the ultraslow modes. Both superluminal and ultraslow modes at higher photonic band gaps are highly affected by thickness disorder. For the superluminal and ultraslow modes at the first photonic band gap, their group velocities are nearly unchanged with thickness disorder.

Polarization and dissociation of exciton in luminescent polymers

It is shown in this paper that the exciton in polymers possesses very large polarizability, and when the electric field is strong enough, the exciton in luminescent polymers is dissociated into a pair of charged polarons. This dissociation can quantitatively interpret the experiment that the luminescence of polymer is heavily quenched by strong electric field.