Realizing Flexible Ultra-Flat-Band Slow Light in Hybrid Photonic Crystal Waveguides for Efficient Out-of-Plane Coupling

Abstract

The realization of slow light with ultra-flat dispersion in hybrid photonic crystal (HPhC) waveguide is systematically investigated. Metal strips have been introduced to the photonic crystal (PhC) waveguide. The dispersion of the odd mode is commendably flattened in the leaky region. Ultra-flat-band slow light with nearly constant average group indices of 192 over 2 nm (i.e., 330 GHz) bandwidth is achieved. Flexible tuning for the ultra-high group index can also be achieved while keeping the normalized delay-bandwidth product fairly high. The introduction of the metal strips is further demonstrated to help reduce the azimuthal angle of the far field and provide a high coupling efficiency.