Young-Tae Byun

Selectively Self‐Assembled Single‐Walled Carbon Nanotubes Using Only Photolithography Without Additional Chemical Process

In this paper, we investigated a novel method of selectively assembling single‐walled carbon nanotubes (SWCNTs) on a silicon (Si) substrate. These SWCNT arrays were fabricated by using only a photolithographic process. Using this technique, SWCNTs could be absorbed on the Si substrate surface without complicated chemical steps. As a result, we successfully fabricated SWCNT‐based multi‐channel patterns. The unmanageable SWCNTs could be easily absorbed on the Si02 surface. This is to advance one step further from the conventional self‐assembled process using octadecyltrichlorosilane (OTS). This technique will provide a useful basis for the implementation of nanostructure‐based field emission transistor (FET) devices. This new process can be used to fabricate SWCNT channels of FET devices.

Optical logic gates based on integrated vertical cavity laser with depleted optical thyristor structure

Optical switches and optical logic gates with AND and OR functionality are demonstrated 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.

Realization of all-optical half adder using XGM in semiconductor optical amplifiers without additional input beam

By using gain nonlinearity characteristics of semiconductor optical amplifier, an all-optical binary half adder at 10 Gbps is demonstrated. No additional input beam such as clock signal or continuous wave light, which is required in many other all-optical logic gates, is used in this design concept. The half adder operates in single mechanism, which is XGM.

10 Gb/s all optical AND gate by using semiconductor optical amplifiers

By using gain saturation of semiconductor optical amplifiers (SOAs), an all-optical AND gate at 10 Gb/s has been successfully demonstrated. Firstly, Boolean (equation omitted) has been obtained using the first SOA with signal B and clock injection. Then, the all-optical AND gate is achieved using the second SOA with signals A and (equation omitted) injection.

Wafer bonding between InP and Ce:YIG(CeY2Fe5O12) using O2 plasma Surface Activation for an Integrated Optical Waveguide Isolator

The wafer bonding of III-V semiconductor materials with garnet thin films has become of increasing technological importance in integration of optical components. The wafer bonding between InP wafer and GGG was demonstrated by using O2 plasma surface activation. The same process was applied to the bonding process of InP/Ce:YIG, which is indispensable for the fabrication of an integrated optical waveguide isolator.

Electrooptic Modulator with InAs Quantum Dots

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.

Photovoltaic Properties of MEH-PPV/DFPP Blend Devices Based on Novel n-type Polymer DFPP

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.

Theoretical and experimental study on ultrahigh-speed clock recovery system with optical phase lock loop using TOAD

10 GHz clock recovery from 40 Gbit/s optical time-division-multiplexed(OTDM) signal pulses was experimentally demonstrated using an optical phase lock loop based on a terahertz optical asymmetric demultiplexer(TOAD) with a local-reference-oscillator-free electronic feedback circuit. The 10 GHz clock was successfully extracted from 40 Gbit/s signals. The SNR of the time-extracted 10 GHz RF signal to the side components was larger than 40 dB. Also we performed numerical simulation about the extraction process of phase information in TOAD. The lock-in frequency range of the clock recovery is found to be 10 kHz.

2.5 Gbit/s all-optical GR logic gate using semiconductor optical amplifiers

전광(all-optical) OR 논리소자가 반도체 광증폭기(SOA)의 이득포화와 파장변환 특성을 이용하여 구현되었다. 전광(all-optical) OR 논리소자는 이득의 비선형성에 의해 동작되므로 SOA의 이득포화를 충분히 얻기 위해 펌프신호는 SOA의 입력단에서 어븀 첨가 광섬유 증폭기(EDFA)에 의해 증폭되었다. 전광 OR 논리소자의 동작특성은 2.5 Gbit/s에서 성공적으로 측정되었다.

Dependence of propagation loss on etching depth in Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As strip-loaded type waveguides

Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As strip-loaded waveguides were fabricated using a broad-beam electron cyclotron resonance (ECR) ion source. It was found that a very smooth etching profile can be obtained by ECR ion etching and the etching rate of Al0.3Ga0.7As is 70 nm min-1. The propagation losses of strip-loaded type III–V compound semiconductor waveguides with various etching depths were studied by the Fabry-Perot cavity method. It was observed that the reflectance at the cleavage increases slightly with etching depth for TE polarization. The propagation loss is measured as 1.5 dB cm-1 for etching depth of 0.7 μm, less than 1 dB cm-1 for 0.8 μm, and 3.5 dB cm-1 for 1.1 μm.