Tae-Yoon Kwon

Designing and understanding directional emission from spiral microlasers

The availability of microlasers with highly directional far-field characteristics is crucial for future applications. To this end we study the far-field emission of active microcavities with a spiral shape using the Schrödinger-Bloch model. We find that they can provide directional emission under the conditions of (i) pumping along the resonator boundary and (ii) for specific resonator geometries. We systematically study the far-field characteristics under variation of the pumped area and the cavity geometry and identify a directionality optimized regime. Our results consistently explain previously obtained experimental results.

Angular emission characteristics of quantum cascade spiral microlasers

We perform ray and wave simulations of passive and active spiral-shaped optical microcavities, comparing our results to experimental data obtained with mid-infrared quantum cascade spiral microlasers. Focusing on the angular emission characteristics, we find that both ray and wave simulations are consistent with the experimental data, showing richly-featured, multidirectional far-field emission patterns in the case of uniform pumping and TM-polarized light. Active cavity simulations using the Schr odinger-Bloch model indicate that selective pumping of the quantum cascade spiral microlasers near the resonator boundary will yield unidirectional laser emission.

Ray and wave dynamical properties of a spiral-shaped dielectric microcavity

We investigate ray dynamical properties and resonance patterns of a spiral-shaped dielectric microcavity in which quasiscarred resonances can be supported. The ray dynamical properties of this open system can be characterized by the steady probability distribution which contains information of the dynamics and the openness of the chaotic microcavity. It is shown that the quasiscarring phenomenon can be understood by considering the unique properties of wave propagation at the dielectric boundary. The bouncing positions of the quasiscarred resonances are explained through a semiclassical quantization condition with Maslov indices. We also show qualitative agreements between the ray dynamical distributions and the wave dynamical distributions obtained from the average over resonance modes.

Oscillatory Lasing Modes In a Coupled Circular Microcavity

We have numerically investigated oscillatory lasing modes in a coupled circular microcavity laser by solving the Schrodinger-Bloch equation with a nonlinear interaction between the light field and the lasing medium. Uniform pumping in the lasing process generates some special patterns as stationary ones, and the patterns are repeatedly shown during the lasing process. In this case, the patterns may be interpreted as linear combinations of the nearly degenerate modes in which the classical trajectory inside the cavity encounter the boundary of the cavity with a nearly critical angle. The numerical results are posted with a brief physical analysis.

Directional Light Output from a Circular Microdisk Laser

Lasing properties of a circular dielectric microdisk laser are investigated. We find the possibility of directional output emissions based on a triangular shaped mode structure which can be constructed by superposition of a few whispering gallery modes. We also find that the directionality of emission beams is enhanced by selectively applied external pumping.

Passive Resonances and Active Lasing Modes in a Chaotic Microcavity

Passive resonances and active lasing modes in a spiral-shaped dielectric microcavity are investigated. We find that the high-Q resonances are whispering-gallery-like modes, and these resonance modes can be easily excited as lasing modes. We also find that the quasi-scarred resonance, which shows strong directional emission beams from the cavity boundary, can be excited with selectively applied external pumping. As a result, we find that the final quasi-stationary lasing pattern exhibits multimode oscillation of whispering-gallery-like mode and quasi-scarred mode