Chil-Min Kim

Lasing characteristics of a Limaçon-shaped microcavity laser

We investigate lasing characteristics of a Limacon-shaped InGaAsP semiconductor microcavity laser. When the cavity is pumped with dc current, the laser generates directional emissions. Near the threshold a series of modes with equidistantly spaced resonant frequencies emit. From the mode spacing we confirm the emission of whispering gallery-type resonance modes. As the injection current increases, a single resonance mode becomes dominant with directional emission. The quality factor of the single mode is obtained near the threshold, which is larger than 22u2009000.

Continuous wave operation of a spiral-shaped microcavity laser

We report a continuous wave laser output of a spiral-shaped InGaAs microcavity laser. When the boundary of the cavity is selectively pumped by current injection with a dc current, the laser generates a directional emission around the notch. We investigate the characteristics of the cw laser operation and observe whispering gallery type modes, whose Q factor is about 7000.

Experimental verification of quasiscarred resonance mode

We have experimentally verified the lasing of a quasiscarred resonance mode (QSRM) in a spiral-shaped InGaAsP microcavity laser by pumping the cavity boundary with current injection. To confirm the lasing of a QSRM, a far field pattern is obtained and six laser emission directions are found; one corresponds to the whispering gallery type modes and the other to a QSRM. By observing the spectrum and lasing thresholds, the lasing characteristics of the QSRM are analyzed.

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.

Tunable Optical Time Delay of Quantum Signals Using a Prism Pair

We describe a compact, tunable, optical time-delay module that functions by means of total internal reflection within two glass prisms. The delay is controlled by small mechanical motions of the prisms. The device is inherently extremely broad band, unlike time delay modules based on slow light methods. In the prototype device that we fabricated, we obtain time delays as large as 1.45 ns in a device of linear dimensions of the order of 3.6 cm. We have delayed pulses with a full width at half-maximum pulse duration of 25 fs, implying a delay bandwidth product (measured in delay time divided by the FWHM pulse width) of 5.8 x 10(4). We also show that the dispersion properties of this device are sufficiently small that quantum features of a light pulse are preserved upon delay.

Resonances in a circular dielectric cavity

Abstract We study resonance distributions in a circular dielectric cavity. It is shown that the decay-rate distribution has a peak structure and the details of the peak are consistent with the classical survival probability time distribution. We also investigate the behavior of the complex resonance positions at the small opening limit ( n → ∞ , n is the refractive index of the cavity). At the large n limit, the real part of complex resonance positions approaches the solutions with different m of Dirichlet problem with a scale n −2 and the imaginary part goes zero as n − 2 m for TM and n − 2 ( m + 1 ) for TE polarization, where m is the order of the resonance.

Directional single mode emission in a microcavity laser

We report directional single mode emission in an InGaAsP semiconductor microcavity laser, which is composed of a circle and an isosceles trapezoid. When exciting a whole cavity, the laser generates a single mode without hopping in two directions over a wide range of continuous injection currents. In the emission spectrum, it is confirmed from the equidistant mode spacing that a scar mode becomes a single lasing mode above the lasing threshold. A numerical analysis of the boundary element method shows that the far-field pattern of the resonance agrees well with that of the experiment.

Terahertz beat frequency generation from two-mode lasing operation of coupled microdisk laser

We propose a coupled microdisk laser as a compact and tunable laser source for the generation of a coherent continuous-wave terahertz radiation by photomixing. Using the Schrödinger-Bloch model including the nonlinear effect of active medium, we find single-mode and two-mode lasings depending on the pumping strength. We explain the transitions of lasing modes in terms of resonant modes that are the solutions of the Schrödinger-Bloch model without active medium and nonlinear interaction. In particular, a two-mode lasing is shown to generate a terahertz oscillating frequency originating from the light beating of two nearly degenerated resonant modes with different symmetries.

Directional and low-divergence emission in a rounded half-moon shaped microcavity

Emission characteristics of a rounded half-moon shaped InGaAsP semiconductor microcavity laser are studied. When excited by pulse current, the laser generates whispering gallery type modes (WGTMs) with equidistant mode spacing in two directions with a narrow divergence angle of 4°. It is confirmed from the mode spacing that the lasing modes are WGTMs. A numerical analysis by the boundary element method shows that the emission direction of resonances well coincides with the experimental result.

Chaos-assisted tunneling in a deformed microcavity laser

We investigate the impact of local dynamics on chaos-assisted tunneling in a highly deformed microcavity whose classical ray dynamics exhibits a small measure of trapezoidal-shaped orbit (TSO) stability islands in a main chaotic sea. These two classically completely decomposed regions in phase space can support resonance modes of their own respectively. Using numerical ray and wave analyses, we show that the emission characteristics of the TSO resonance mode are determined by local ray dynamics near TSO islands. The emission characteristics of the other high-Q resonance modes, on the other hand, are governed by usual ray-wave correspondence. We experimentally demonstrate that the TSO emission mode can be lased without selective excitations by devising a half-moon shaped highly deformed cavity. And we also show that the emission characteristics of the TSO lasing modes are well explained by numerical ray and wave analyses.