Reduction of mode Q-factor due to coupling between fundamental and first order whispering-gallery modes in coupled microdisks

Abstract

The mode characteristics for twin coupled microdisks are investigated by finite-difference time-domain technique. In the coupled microdisks, the same order whispering-gallery (WG) modes can form coupled modes with split mode wavelengths. We find that the coupled fundamental and first order WG modes can have anticrossing mode coupling as their wavelengths approach the same value in some case, which prevents the cross of the coupled mode wavelengths. The anticrossing mode coupling greatly reduces the coupled mode Q-factor, because the coupled mode field distribution transfers between the fundamental and the first order WG modes.