Experimental controlling of Fano resonance in indirectly coupled whispering-gallery microresonators

We experimentally studied the transmission spectrum of a coupled resonator structure in which a low-Q microdisk and a high-Q microtoroid indirectly interact with each other mediated by a fiber taper. Asymmetric Fano resonances were observed and could be controlled to change periodically by adjusting the distance between the two microresonators. It is revealed that the Fano resonance originates from the coupling of the two modes belonging to the two microresonators. The observed period of distance change is around 8 mu m, which shows good agreement with the theoretical prediction by the beat of multiple propagating modes in the fiber taper. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3675571]