Highly Collimated Lasing Emission from a Peanut-Shaped Micro-Cavity

Highly collimated lasing from a series of peanut-shaped micro-cavities were observed. The lowest divergence is about 1.2deg which is as small as the pure diffraction divergence of a plane wave propagating through an opening of the cavity size. It is shown that the lensing effect of the circular boundary plays a crucial role in generating the highly collimated lasing emissions. From ray and wave dynamic analyses, we find that the peanut-shaped micro-cavity is optimal for the lasing emission of very narrow divergence