Deformed wavelength-scale microdisk lasers with quantum dot emitters

A recent development in the fabrication of quantum dot based microdisk lasers is the ability to reduce their dimensions to approximately the emission wavelength. In this chapter we show that deforming the cross-sectional shape of such disk lasers can lead to highly directional light output from high-quality 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. The fact that the quality factor stays high is explained by the existence of partial barriers in the phase space of ray dynamics. These two mechanisms make it possible to control the output properties of wavelength-scale lasers.