Enhanced Directionality of Emission of the On-Threshold Modes of a High Refractive Index Microdisk Laser Due to a Small Piercing Hole

We study, using the integral-equation-based in-house guaranteed-convergence numerical code, the effect of a circular air hole on the frequency, threshold gain and directionality of emission of the whispering-gallery modes of a two-dimensional model of circular-disk microcavity laser. We show that a small hole can enhance the directionality greatly and leave the threshold gain intact, if disk's refractive index is large enough and hole's location is chosen properly. This location should be close to the area where the same uniform disk, if illuminated with a plane wave, displays a broadband focusing in the form of hot spot called photonic jet.