Analytical and Experimental Demonstration of Fano Resonance in One-Dimensional Photonic Crystal Cavity and Waveguide System

Fano resonance is ubiquitous in many areas, including photonics. These resonances occur when a discrete quantum state (resonant mode) interferes with a continuum band of states [1]. A conventional Lorentzian cavity mode has a symmetrical shape with respect to its resonant wavelength. In comparison, a Fano resonance spectrum has an asymmetric line profile. This asymmetry is typically quantified by the Fano parameter which is given by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$q=\cot \delta$</tex>, where δ is the phase shift of the continuum with respect to the discrete state. The asymmetric line shape of Fano resonance with high extinction ratio and high Q factors are very effective for sensing, on-chip photonic modulator [2] and photonic switching [3] applications.