[Show abstract][Hide abstract] ABSTRACT: A direct wafer bonding process necessary for GaAs-on-insulator (GOI) fabrication with high thermal annealing temperatures was studied by using PECVD oxides between gallium arsenide and silicon wafers. In order to apply some uniform pressure on initially-bonded wafer pairs, a graphite sample holder was used for wafer bonding. Also, a tool for measuring the tensile forces was fabricated to measure the wafer bonding strengths of both initially-bonded and thermally-annealed samples. GaAs//Si wafers with 0.5-m-thick PECVD oxides were annealed from . Maximum bonding strengths of about 84 N were obtained in the annealing temperature range of . The bonded wafers were not separated up to . As a result, the GOI wafers with high annealing temperatures were demonstrated for the first time.
Korean Journal of Materials Research 01/2006; 16(10):652-655.
[Show abstract][Hide abstract] ABSTRACT: Optical characteristics in polymer films of MEH-PPV/DFPP blends were for the first time investigated. DFPP (N, N'-diperfluorophenyl-3,4,9,10-perylenetetracarboxylic diimide) used here was a novel n-type polymer, which had good stability in air and solubility in common solvents. For a 1:9 DFPP:MEH-PPV blend, highly efficient quenching of photoluminescence (PL) was observed. In addition, the photocurrent responses of these MEH-PPV/DFPP photovoltaic cells were measured. When the light intensity was , short-circuit photocurrent densities were two times higher than those of single layer MEH-PPV devices.
[Show abstract][Hide abstract] ABSTRACT: We have fabricated and measured electrooptic modulator using coupled stack InAs/InGaAs quantum dots. The height of the quantum dot is 16 nm and quantum dots are stacked including an InGaAs capping layer. The peak wavelength of photoluminescence is 1260 nm at room temperature and 1158 nm at 12 K. The operation characteristics of the quantum dots show high modulation efficiency of electrooptic modulator at 1550 nm compared to that of existing III-V bulk and MQW type semiconductor. The measured switching voltage () is 540 and 600 mV, for TE mode and TM mode, respectively. From the results, the modulation efficiency can be determined as 333.3 and for TE and TM modes. The results reported here may lead to the design and fabrication of a novel electrooptic modulator with low switching voltage and high efficiency.
[Show abstract][Hide abstract] ABSTRACT: For the faster switching speed and the lower power consumption, we optimized the structure of a fully depleted optical thyristor (DOT) by the depletion of charge at the lower negative voltage. The fabricated optical thyristor shows sufficient nonlinear s-shape I-V characteristics with the switching voltage of 2.85 V and the complete depletion voltage of -8.73 V. In this paper, using a finite difference method (FDM), we calculate the effects of parameters such as doping concentration and thickness of each layer to determine the optimized structure in the view of the fast and low-power-consuming operation.
[Show abstract][Hide abstract] ABSTRACT: The nonreciprocal phase shift characteristics of infinite slab optical waveguides with magneto-optic materials in the cladding layer was calculated at 1.55 for optical isolators. The infinite slab waveguide structures considered in this paper were as follows. rho magneto-optic materials used as a cladding layer were Ce:YIG and LNB(LuNdBi)(FeAl)),). Their specific Faraday rotations Θ are 4500/cm, 500/cm at wavelength 1.55 respectively. The guiding layer with multi-quantum well structure was used, and it consists of 1.3Q and InGaAs. In order to investigate the effect of evanescent field penetrating the cadding, layer, guiding mode characteristics were calculated for the cases when the substrate is InP and air. We calculated the minimum lengths of 90 nonreciprocal phase shifters and their optimum guiding layer thicknesses in various optical waveguide structures.res.s.
[Show abstract][Hide abstract] ABSTRACT: We fabricated a P-I-i-I-N waveguide phase modulator with significant phase shift for the TE mode but negligible for the TM mode. We selected the P-I-i-I-N structure to cause a phase shift about the TM mode. The wavelength of was measured for both the TE and TM modes, respectively. As a result, the measured phase shift efficiency () by using the Fabry-Perot resonance method was for TE-polarized light. Also, no modulation was observed for TM-polarized light.
[Show abstract][Hide abstract] ABSTRACT: Bistable laser diodes (BLDs) will play an important role as all-optical switching elements for future optical communications networks and computing systems. In this study, we report the optical bistability in a multisection distributed feedback laser diode (DFB-LD) using a split-step time-domain model. Simulation results show that the three-section DFB-LD works as a flip-flop in response to the set/reset optical pulse whose switching time is a few ns and whose switching energy is a few pJ.
Japanese Journal of Applied Physics 01/2003; 42. · 1.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: By using a semiconductor optical amplifier and a cross-phase modulation wavelength converter, fundamental all-optical logic gates including NOT, AND, NOR, XOR, and XNOR have been newly proposed and implemented. Realization of these all-optical logic gates will bring up not only all-optical networks but also all-optical computing and signal processing.
Journal of the Optical Society of Korea 01/2002; 6(4):165-171. · 1.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this work, we studied the effect of chirped grating on optical bistability in λ/4-shifted semiconductor distributed-feedback(DFB) devices, such as an etalon with nonlinear mirrors, a λ/4-shifted DFB waveguide and aλ/4-shifted DFB laser amplifier. We found that chirped DFB devices exhibit bistable switching at a lower input power.OCIS code : 050.2770, 190.1450, 190.5970, 230.0230.
Journal of the Optical Society of Korea 01/2001; 5(1):5-8. · 1.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: By using an XPM (Cross Phase Modulation) wavelength converter, an all-optical AND gate, which is one of six fundamental logic gates, has been demonstrated. The wavelengths for probe and pump signals are 1553.8 and 1545 nm, respectively. First, characteristics of the XPM wavelength converter have been studied. When both probe and pump signals are driven by high power, the output power of the XPM wavelength is high. Based on this fact and the experiment, the all-optical AND gate has been porved. Probe and pump signals are transformed to pulse signals by using Mach-Zehnder modulator, which is induced by a pulse generator. Square pulse signals that are similar to the format of NRZ signals have been generated. By coupling two pulse signals into the XPM wavelength converter, AND characteristics in substantiated.
Journal of the Optical Society of Korea 01/2001; 5(1):25-28. · 1.02 Impact Factor