Directional laser emission from a wavelength-scale chaotic microcavity.

We demonstrate directional output from a deformed disk laser of dimensions comparable to the emission wavelength. Unlike larger deformed cavity lasers, which exhibit universal output directionality determined by chaotic ray dynamics, the far-field patterns differ between lasing modes. The directional emission results from weak coupling of isotropic high-quality modes to anisotropic low-quality modes, combined with chiral symmetry breaking of clockwise and counterclockwise propagating waves. This mechanism makes it possible to control the output properties of wavelength-scale lasers.