Tunable slow light based on magnetic-fluid-infiltrated photonic crystal waveguides

Tunable slow light is proposed with photonic crystal structures infiltrated with magnetic fluids and/or applying externally magnetic field to the infiltrated devices. The W0.9 line-defect waveguide is formed within the heterostructure-slab with triangular lattice. The plane-wave expansion method is employed to investigate the slow light properties numerically. Two different criteria determining the bandwidth are adopted to quantify the slow light performance. Under the low dispersion (constant group index) criterion, the wavelength bandwidth Delta lambda centered at a wavelength of lambda 0 = 1550 nm can be tuned in the range of 18.45-28.32 nm (4.73-9.28 nm) when the infiltrated magnetic fluid concentration increases from 0.25% to 1.75%. The corresponding average group index decreases from 21.39 (22.66) to 18.34 (18.04). Similarly, the local magnetic field factor (i.e. the strength of externally applied magnetic field) can tune the wavelength bandwidth around 1550 nm (under the constant group index) and the average group index in the range of 6.60 nm-10.42 nm and 15.91-14.69, respectively. The results of this work may be helpful for experimentally designing and realizing the magnetic-fluid-based tunable slow light.