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/λ = 0.610 to a/λ = 0.628. Its operating frequency range provides also a huge angle magnification from 20.6° to 59.9°. 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 finitedifference time-domain calculations with 3° angle of incidence, it is obtained that the light is diffracted in a range between 20.6° and 59.9° 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.
Melike Gumus, Ibrahim Halil Giden, and Hamza Kurt, "Enhanced super-prism effect with self-collimation by dispersion management in C1 symmetric photonic crystals," Proc. SPIE 10541, Photonic and Phononic Properties of Engineered Nanostructures VIII, 105411L (Presented at SPIE OPTO: February 01, 2018; Published: 21 February 2018); https://doi.org/10.1117/12.2289112.
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