Woon Kyung Choi

Optical properties of selectively oxidized vertical cavity laser with depleted optical thyristor structure

The authors show that the optical properties of selectively oxidized vertical cavity lasers with a depleted optical thyristor structure have a low threshold current and high sensitivity to input optical light. The oxidized thyristor laser clearly shows a nonlinear s-shaped current-voltage and lasing characteristics. A switching voltage of 5.24V, a holding voltage of 1.50V, and a very low threshold current of 0.65mA are measured, making these devices attractive for optical processing applications.

Optical AND/OR gates based on monolithically integrated vertical cavity laser with depleted optical thyristor structure

Latching optical switches and optical logic gates with AND and OR functionality are demonstrated for the first time by the monolithic integration of a vertical cavity lasers with depleted optical thyristor structure. The thyristors have a low threshold current of 0.65 mA and a high on/off contrast ratio of more than 50 dB. By simply changing a reference switching voltage, this single device operates as two logic functions, optical logic AND and OR. The thyristor laser fabricated by using the oxidation process and has achieved high optical output power efficiency and a high sensitivity to the optical input light.

Lasing characteristics of InGaAs∕InGaAsP multiple-quantum-well waveguide-type depleted optical thyristor with vertical window

This study demonstrates the lasing characteristics of InGaAs∕InGaAsP multiple-quantum-well waveguide-type depleted optical thyristor using the vertical window. The measured switching voltage and current are 3.36V and 10μA, respectively. The lasing threshold current is 131mA at 25°C. The output peak wavelength is 1570nm at a bias current of 1.22 Ith and there is no input signal. The vertically injected depleted optical thyristor shows very good isolation between input and output signals.

Lasing characteristics of InGaAs/InGaAsP multiple-quantum-well optical thyristor operating at 1.561 μm

We present a demonstration of a waveguide-type depleted optical thyristor laser diode with InGaAs/InGaAsP multiple-quantum-well structure. The measured switching voltage and current are 4.63 V and 10 μA, respectively. The holding voltage and current are, respectively, 0.59 V and 20 μA. The lasing threshold currents at 25 °C and 10 °C are 111 mA and 72.5 mA, respectively. The lasing wavelength is centered at 1.561 μm at a bias current equal to 1.41 times threshold.

Triangular ring resonator incorporating total internal reflection mirror and compact multimode interference coupler

We report fabrication and measurements on novel triangular ring resonators with extremely small multimode interference couplers and total internal reflection mirrors. Free spectral range and on-off ratio are 256 GHz and 14 dB respectively.

Three-guide coupled rectangular ring lasers with total internal reflection mirrors

The lasing characteristics of three-guide coupled ring lasers using the self-aligned total internal reflection (TIR) mirrors were investigated numerically and experimentally. The rectangular laser cavity consists of four low loss TIR mirrors and an output coupler made out of passive three coupled waveguides. Two different lasers having active section lengths of 250 and 350 μm and total cavity lengths of 580 and 780 μm are fabricated. For both devices lasing thresholds of 38 mA is obtained at room temperature and under CW operation. Lasing is predominantly single mode with the side mode suppression ratio better than 20 dB.

Micro ring cavity resonator incorporating total internal reflection mirrors

We investigate the properties of a multimode-interference (MMI) coupled micro ring cavity resonator with total-internal-reflection (TIR) mirrors and a semiconductor optical amplifier (SOA). The TIR mirrors were fabricated by the self-aligned process with a loss of 0.7 dB per mirror. The length and width of an MMI are 142 &mgr;m and 10 &mgr;m, respectively. The resulting free spectral range (FSR) of the resonator was approximately 1.698 nm near 1571 nm and the extinction ratio was about 17 dB. These devices might be useful as optical switching and add-drop filters in a photonic integrated circuit or as small and fast resonator devices.

Demonstration of all optical logic gates by single/differential typed vertical cavity laser with depleted optical thyristor

Latching optical switches and optical logic gates with AND or OR, plus the INVERT functionality are demonstrated for the first time by the monolithic integration of a single and differential typed vertical cavity lasers with depleted optical thyristor (VCL-DOT) structure with a low threshold current of 0.65 mA, a high on/off contrast ratio of more than 50 dB, a high slope efficiency of 0.38 mW/mA, and high sensitivity to input optical light. By simply changing a reference switching voltage, this single-typed device operates as two logic functions, optical logic AND and OR. The differential-typed VCL-DOTs operate also as all logic gates, AND/NAND, OR/NOR, and INVERT function by simple change of a reference input light power. The thyristor laser fabricated by using the oxidation process shows a high optical output power efficiency and a high sensitivity to the optical input light.

Oxide confined vertical cavity laser - depleted optical thyristor

This study shows the optical properties of a vertical cavity laser(VCL) - depleted optical thyristor(DOT) fabricated using selective oxidation. The oxide confined PnpN VCL-DOT clearly shows the nonlinear s-shaped current-voltage and lasing characteristics.

Depleted optical thyristor using vertical injection method for good isolation between input and output

Recent DOT studies have focused on waveguidetype structure for laser diode operation in the long wavelength. The first demonstration of the waveguide-type DOT-LD was reported by our team. However, these WDOT-LDs have several problems such as the low confinement factor, the large sensitivity dependence on input light wavelength, and moreover, the leaking input light into the output as shown Fig. 1.