Partially directional microdisk laser with two Rayleigh scatterers.

We report a partially directional microdisk semiconductor laser with subwavelength-scale boundary perturbations for asymmetric backscattering of counterpropagating whispering gallery modes. Unlike the previous approaches based on optical bistability, the directionality and chirality of the laser modes can be fine-tuned and partially controlled by adjusting the dimension, shape, and relative positions of Rayleigh scatterers on the microdisk perimeter. The controlled directionality is investigated using numerical simulations and experiments for wavelength-scale microdisk resonators with an azimuthal mode number of 5.