Crossed chiral band approximation for wide-band self-collimation of light
Journal of Physics D: Applied Physics
Institute of Physics Publishing
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We propose a perspective to the evaluation of the wide bandwidth phenomenon for low-symmetric photonic structures, by introducing the band tailoring and chiral band approximation on the self-collimation effect. In the case of the crossing of the bands, we claim the excitation of the lower mode can provide the utilization of the entire bandwidth by suppressing the intersection regions where the frequencies tend to mix. Thereby, we design broadband self-collimation capable, defect-free photonic structures and examine their performances. A fractional bandwidth of 0.35 (a/λ = 0.429 − 0.607) and 0.37 (a/λ = 0.481 − 0.701) are achieved for radii of r = 0.25a and r = 0.23a, respectively. We explore the full-range collimation by using transmission and E-field intensity analyses in addition to band diagrams and group velocity dispersions. Moreover, we indicate all-angle collimation validity even for highly tilted sources up to an angle of 80◦ .