All-optical analog to electromagnetically induced transparency with coupled nanobeam cavities and Mach–Zehnder interferometer

Abstract

We design and experimentally demonstrate an all-optical analog to electromagnetically induced transparency with a Mach–Zehnder interferometer nanostructure with waveguides that are side-coupled to photonic crystal nanobeam cavities. When the phase difference between the two interferometer beams is designed to be odd multiples of π and the resonance peaks of the two cavities intersect, the transparency resonance occurs. The measured transparency linewidth is 0.6 nm, which is much narrower than the destructive interference linewidth carried out by the interferometer. When the phase difference between the two beams increases slightly, the destructive interference wavelength decreases accordingly and causes the transparency line shape to change into a Fano-like line shape. By replacing the single cavity with coupled cavities, multiple transparency phenomena can also be observed and further enhance the quality factor of the cavity.