Soo-Young Lee

Unidirectional lasing from a microcavity with a rounded isosceles triangle shape.

We report that unidirectional lasing emission can be generated from a rounded isosceles triangular microcavity within a low nkD range, where n is the refractive index, k is the vacuum wave number, and D is the characteristic size of the microcavity. It is shown that unidirectional resonance modes have relatively high-Q values and in a nonlinear dynamic model appear as stationary lasing solutions with a low threshold. The formation of a whispering-gallery-type pattern along the rounded part on the symmetry axis is responsible for the unidirectionality of the resonances.

Directional interacting whispering-gallery modes in coupled dielectric microdisks

We study the optical interaction in a coupled dielectric microdisks by investigating the splitting of resonance positions of interacting whispering-gallery modes (WGMs) and their pattern change, depending on the distance between the microdisks. It is shown that the interaction between the WGMs with odd parity about the y axis becomes appreciable at a distance less than a wavelength and causes directional emissions of the resulting interacting WGMs. The directionality of the interacting WGMs can be understood in terms of an effective boundary deformation in ray dynamical analysis. We also discuss the oscillation of the splitting when the distance is greater than a wavelength.

Lasing modes in a spiral-shaped dielectric microcavity

The resonance patterns and lasing modes in a spiral-shaped dielectric microcavity are investigated through passive and active medium calculations. We find that the high-Q resonance modes are whispering-gallery-like modes, and these resonance modes can be easily excited as lasing modes. We also find that the quasi-scarred resonance mode, which shows strong directional emission beams from the cavity boundary, can be excited with selectively applied external pumping. Through a spectral analysis of the time evolution of the light field, the competition between these lasing modes is discussed.

Characteristics of Lasing Modes in a Spiral-Shaped Microcavity

We have numerically investigated the characteristics of the lasing modes in a spiralshaped microcavity laser by solving the Schrodinger-Bloch equation with the nonlinear interaction between the light field and the lasing medium. For overall uniform pumpings, we have found whispering gallery type modes with no directional emission. In case of local pumpings, however, whispering gallery type, quasi-scarred type, and complex type patterns appear in the course of time. Especially, we have also found the evidence of directional emissions from the notch part of the cavity.

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