In this work, a hollow cylindrical optical microcavity is numerically investigated by finite-difference time-domain simulations. Enhancement of a single whispering-gallery mode (WGM) is realized by inserting a periodic hole array into the hollow cylindrical structure. Line of missing holes acts as an optical microcavity. Electric and magnetic field profiles of both typical and enhanced resonant modes are presented. Variations of the single-mode resonant frequency and its quality (Q) factor are studied as a function of structural parameters, which are hole radius, width of the missing hole line, and number of holes. This work shows that the hole radius and the width of the missing hole line strongly affect both the resonant frequency and Q factor while varying the number of holes does not influence the resonant frequency, but they monotonically change the Q factor. This work provides information for designing and optimizing an WGM optical microcavity.
