Wavelength-scale deformed microdisk lasers

We investigate lasing and output directionality of limacon-shaped microdisk lasers of dimensions comparable to the emission wavelength. The far-field patterns are shown to differ between lasing modes, unlike in large cavities where lasing modes exhibit universal emission directionality determined by chaotic ray dynamics. Unidirectional emission is obtained for certain modes in the wavelength-scale cavities. It results from weak coupling of nearly isotropic high-quality resonances to anisotropic low-quality resonances, combined with chiral symmetry breaking of clockwise and counterclockwise propagating waves. The latter is described by an extended ray dynamics which includes the Goos-Haenchen shift and the Fresnel filtering. Mode hybridization and wave effects in open cavities make it possible to control the output properties of individual lasing modes in wavelength-scale lasers.