Enhanced and decreased group velocity in compositionally graded films of nonspherical particles

Lei Gao; Yu Ma

doi:10.1117/12.676450

8 September 2006 Enhanced and decreased group velocity in compositionally graded films of nonspherical particles

Lei Gao, Yu Ma

Proceedings Volume 6328, Nanomodeling II; 63280G (2006) https://doi.org/10.1117/12.676450
Event: SPIE Optics + Photonics, 2006, San Diego, California, United States

Abstract

We investigate the group velocity of electromagnetic signals in compositionally graded films consisting of nonspherical particles. The theory is first based on generalized effective medium approximation to obtain the local dielectric function tensor in a x slice. Then, the effective dielectric tensor of the graded film is directly determined, and the group velocities for ordinary and extraordinary waves in the film are derived. It is found that the group velocity is dependent on the graded profile and the particles' shape. For a power-law graded profile f(x) = ax^m, increasing m results in the decreased extraordinary group velocity. Such a decreased tendency becomes significant when the incident angle increases. Moreover, enhanced or decreased group velocity may be achieved when the geometric shape of particles is non-spherical. In detail, oblate particles with large depolarization factor L results in large velocity enhancement and prolate one with small L leads to decreased velocity for normal incidence. Therefore, the non-spherical shape and graded profile play crucial roles in determining the magnitude of the group velocity in compositionally graded film.

Citation Download Citation

Lei Gao and Yu Ma "Enhanced and decreased group velocity in compositionally graded films of nonspherical particles", Proc. SPIE 6328, Nanomodeling II, 63280G (8 September 2006); https://doi.org/10.1117/12.676450

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