Joon Huh

A high-extraction-efficiency nanopatterned organic light-emitting diode

To improve light extraction from organic light-emitting diodes (OLEDs), we introduced a photonic crystal pattern into the glass substrate of an OLED. The periodic modulation converts the guided waves in the high-refractive-index indium-tin-oxide/organic layers into external leaky waves. We used the finite-difference time-domain method to optimize the structural parameters of the photonic crystal pattern and to analyze the microcavity effect by the metallic cathode of the OLED. With the use of an optimized photonic crystal pattern, an increase of over 80% in the extraction efficiency of the OLED is expected theoretically. An increase in the extraction efficiency of over 50% was achieved experimentally, without detriment to the crucial electrical properties of the OLED.

Characteristics of modified single-defect two-dimensional photonic crystal lasers

The resonant modes found in a modified single-defect two-dimensional photonic crystal slab structure are theoretically and experimentally studied. There exist several modes in the band gap: doubly degenerate (dipole and quadrupole modes) and nondegenerate (hexapole and monopole modes). Among them, the monopole mode specifically attracts our interest because of its nondegeneracy, good coupling with the gain medium, and existence of the intensity minimum at the center of the cavity, which would open up the chance for the electrically driven single-defect laser. The nondegenerate hexapole mode, a special type of whispering gallery mode, has a very high quality factor. We have fabricated two types of modified single-defect lasers, i.e., air-based free-standing and SiO/sub 2/-based epoxy-bonded structures. Rich lasing actions in both structures are experimentally observed under optically pulsed pumping conditions at room temperature. In the free-standing slab structure, photons are strongly confined in vertical direction, and the lasing operations of all resonant modes with low thresholds are obtained. Especially, the nondegenerate monopole-mode laser is confirmed to have a large spontaneous emission factor of >0.06, estimated by analyzing rate equations. In the SiO/sub 2/-based slab structure, thermal properties are improved at the expense of vertical losses.

Nondegenerate monopole-mode two-dimensional photonic band gap laser

We propose and demonstrate photonic band gap lasing action from a nondegenerate monopole-mode, high-quality factor cavity. By optical pumping at room temperature, the monopole-mode laser is realized and identified from its mode shape, spectrum, and polarization. The monopole-mode laser shows nondegeneracy and genuine two-dimensional oscillation with incident threshold pump power less than 0.3 mW. This laser mode has a small modal volume of ∼4.5(λ/2nslab)3 and shows a quality factor of larger than 1900, estimated from the spectral linewidth below threshold.

Nondegenerate monopole mode of single defect two-dimensional triangular photonic band-gap cavity

The two-dimensional monopole mode is investigated as a candidate for a nondegenerate photonic band-gap (PBG) cavity mode. This monopole mode formed in a single defect triangular PBG cavity is truly nondegenerate and remains nondegenerate in the sense that the introduction of asymmetry does not result in splitting of the mode. Several methods to tune the resonant frequency of the mode are studied. The radii, positions, and shapes of the nearest-neighbor air holes are varied in this analysis using the three-dimensional finite-difference time-domain calculation. The quality factor of the monopole mode formed in a slab waveguide structure is found to be larger than that of the dipole mode when the shape of the nearest-neighbor holes is elliptical.

Simultaneous Monitoring Technique for OSNR and PMD Based on Four-Wave Mixing in SOA

We report a simultaneous monitoring technique for OSNR and PMD based on the FWM in a semiconductor amplifier. This technique can monitor the OSNR and PMD with accuracy of +0.3 dB and +10 ps, respectively.

Four-Wave Mixing Compensator based on Highly Nonlinear Fiber

We demonstrate a new FWM compensation technique by using a highly nonlinear fiber and a pump laser. The results show that proposed technique could effectively suppress the FWM crosstalk generated in the transmission fiber and improve the systems performance.

Enhanced performance of NOLM-based 2R regenerator by using optical bandpass filter

We report on the operation of the 2R regenerator based on the nonlinear optical loop mirror (NOLM) with non-soliton pulses by utilizing an optical bandpass filter at the output of the NOLM. For the proper operation, the bandwidth and offset of this filter should be optimized.

Fiber-based optical phase conjugation with Raman amplification

We improve the maximum conversion efficiency of the fiber-based optical phase conjugation by using Raman amplification despite the decreased stimulated Brillouin scattering threshold.

Temperature-independent fiber-based optical phase conjugation

We have investigated the effect of temperature variation on the performance of fiber-based optical phase conjugation (OPC) module. The results show that the bandwidth of the fiber-based OPC module could be reduced significantly by temperature variation. However, it would be difficult to control the temperature of bulky fiber spool precisely. To solve this problem, we have proposed and demonstrated a simple method to compensate the bandwidth reduction (caused by temperature variation) by adjusting the pump power. Using this method, we could maintain the 1-dB bandwidth of fiber-based OPC module within 5% even when the ambient temperature was varied as much as plusmn15 degC

A Study of Laboratory Measurement of EO GRD Resolution for Airborne EO/IR Sensor

ABSTRACT EO GRD(Ground Resolved Distance) resolution of airborne EO/IR(Electro-Optical/Infrared) sensor is a critical factor in test and evaluation for EO sensor performance. We propose the laboratory measurement set-up for EO GRD by constructing optical collimator which includes integrated sphere, blackbody, equivalent 3-bar target and 6 DOF motion simulator. GRD is measured in the photographic imagery of bar targets by 3 different distances for 3 EO/IR sensors and the measured results were analyzed statistically. We found that at least 7 sheets of imagery are needed in order to obtain meaningful EO GRD. The result of statistical analysis shows that the distribution of the measured GRD is nearly symmetric about the average GRD, and the better imagery ratio above the average GRD is about 40 ∼ 70%. Also from the best GRD analysis, it is estimated that the design goal for EO GRD should be 30% superior to the required GRD.Key Words : EO/IR(Electro-Optical/Infrared), Sensor(센서), GRD(Ground Resolved Distance), Imagery(영상)