Resonance splitting in microring resonators constructed from organic nanofiber active waveguides

Abstract

Abstract We investigated the resonance splitting in microring resonators (MRRs) constructed from nanofibers of organic dye, which function as active waveguides. The MRRs were fabricated by connecting both end parts of a nanofiber so that they contacted with each other in a side-by-side manner with a contact length of ∼5 μm by micromanipulation on a substrate. We observed that the shape and width of the resonance peaks were sensitively changed by changing the contact length. Moreover, the resonance peaks split into a doublet by tuning the contact length. We propose that the splitting is due to the coupling between the counterclockwise and clockwise traveling modes within a ring. The coupling can be induced by the reflection of traveling light at the end faces of the nanofiber in the connection region. Since this mechanism leads to a strong mode coupling, the resonance splitting is resolved even though the resonance peaks of the nanofiber MRRs are relatively broad (the Q-factors of up to ∼2000).