Enhanced super-prism effect with self-collimation by dispersion management in C-1 symmetric photonic crystals

Abstract

Photonic crystals ( PhCs) are artificial wavelength-scale periodic structures that enable the manipulation of light propagation and possess intriguing dispersive characteristics such as negative refraction, self-collimation, slow/ fast light and super-prism. Among these properties, here we present compact low-symmetric PhCs exhibiting S-vector super-prism effect with high diffraction ability. Each unit-cell of square lattice PhC structure includes two dielectric rods in air background and it provides a high-resolution super-prism effect for transverse-magnetic bands. Theoretical calculations of band structures as well as equi-frequency contours are conducted by solving Maxwell's equations with plane-wave expansion method to investigate the superprism effect of the proposed PhCs. Such asymmetric PhC configuration has a wide wavelength sensitivity from a/lambda = 0.610 to a/lambda= 0.628. Its operating frequency range provides also a huge angle magnification from 20.6 degrees to 59.9 degrees. In terms of diffraction ability, the proposed PhC structure overcomes the problems of irregular beam generation and irregular beam divergence in usual PhC structures. According to finite-difference time-domain calculations with 3 degrees angle of incidence, it is obtained that the light is diffracted in a range between 20.6 degrees and 59.9 degrees inside the structure with a high wavelength sensitivity. That effect could be used for wavelength demultiplexing applications. Moreover, the numerical time-domain calculations are made to verify the theoretical analyses. Depending on the incidence angle, the light propagating inside the PhC medium steers up/ down perfectly with a collimated behavior. Such highly wavelength sensitive self-collimated light diffraction property can be used to separate propagating beam at the output channels with low cross-talks in compact photonic integrated systems. Experimental verification of the intended superprism effect is also conducted in the microwave frequencies and a quite well wavelength sensitivity effect is observed.