Dae-Seo Park

Photonic Crystal-Based GE-PON Triplexer using Point Defects

In this paper, we newly propose an optical triplexer which is one of key components in Gigabit Ethernet Passive Optical Network for Fiber-To-The-Home network. Based on a photonic crystal structure with local point defects, two types of optical triplexers were optimally designed. The size-tuned optical triplexer shows the extinction ratios of -17.8 dB, -14.4 dB, and -15.9 dB for the wavelengths of 1310nm, 1490nm, and 1550 nm, respectively. And the index-tuned optical triplexer shows the extinction ratios of -19.24dB, -17.09dB, and -22.68dB for the wavelengths of 1310nm, 1490nm, and 1550 nm, respectively. The size of the proposed optical triplexers were about 4 × 3 μm2.

Effect of Incident Beam Width on Light Transmission Enhancement by Bow-Tie-Shaped Nano-Aperture

In this paper, a bow-tie-shaped nano-aperture is proposed to enhance light transmission and obtain a tiny beam spot. The transmission and focusing characteristics of the proposed aperture are analyzed numerically using a dispersive three-dimensional finite-difference time-domain (3D-FDTD) method. The spot size and transmittance enhancement of the light transmitted through the optimized aperture are approximately λ/20 and 400 times, respectively. In contrast to the bowtie antenna, the proposed nano-aperture has a bow-tie-shaped opening at its center and its surroundings are filled with metal. Thus, the transmittance enhancement can be further increased by extending the interaction area between an incident beam and the metal portion of the nano-aperture, which is accomplished by increasing the beam width of an incident light.

Design of wavelength demultiplexer based on photonic crystal filter structures

In this paper, we present a newly proposed optical demultiplexer for an application of optical communication network. We designed the photonic crystal optical demultiplexer based on filter structures. The proposed device was designed by utilizing the plane wave expansion method and its performance was analyzed by using the finite difference time domain method. The proposed demultiplexer shows the extinction ratios of -41.6 dB and -78.6 dB for the wavelengths of 1.31 mum and 1.55 mum, respectively.

Simultaneous Measurement of Thickness and Refractive Index of Transparent Material Using a Collimated Beam Having a Finite Radius

We propose a new measuring technique based on optical low-coherence reflectometry that enables us to determine the refractive index and the geometrical thickness of a transparent sample by one-time scanning only. By passing a collimated beam having a finite size through the edge of the sample, the refractive index and the geometrical thickness can be determined simultaneously from the comparison of interferograms generated by two kinds of reflected beams. In this study, a refractive index could be determined with the accuracy of , and its accuracy would be enhanced by using a more precise translator and a thicker sample.

Measurement and Analysis of Light Scattering of Au Pads on PCB Surface to Extract Scattering Parameters

In this study, the influence of surface roughness on light scattering from Au pads on a PCB surface was investigated. Angular distributions of light scattered from Au pads with different surface roughness were measured for several incident angles. Diffusely-scattered light could be separated by using the fact that the amount of specularly-scattered light was directly related to surface roughness. The separated diffuse term was curve-fitted with a physics-based model, and then the related scattering parameters were extracted and compared with measured parameters.

Photonic Crystal-Based WDM Filter for Integrated Optical Triplexer Transceiver

We propose the new concept of an optical triplexer for an application of Gigabit Ethernet Passive Optical Network (GEPON) to Fiber-To-The-Home (FTTH) network. Based on a photonic crystal structure with local point defects, the optical triplexer is optimally designed. The proposed device is analyzed by the plane wave expansion method and its performance characteristics are evaluated by the finite-difference time-domain method. The optical triplexer proposed here is designed to have a compact size of about 4 × 3 μm2 and the extinction ratios of -32.33 dB for 1310 nm, -19.84 dB for 1490 nm and -29.93 dB for 1550 nm, respectively.

Measuring near-field optical distributions emitted from chip surface of photonic crystal patterned light emitting diodes

In our study, the distribution of the near-field close to the chip surface of Photonic Crystal (PhC)-patterned GaN-based blue LED is measured with Near-field Scanning Optical Microscopy (NSOM). The blue LED has the layer structure consisted of Sapphire substrate - n-GaN - Multi Quantum Well (MQW) - p-GaN - ITO, where the PhC pattern is incorporated onto the top p-GaN layer. When the current is applied to the MQW, the light is emitted out of LED and the near-field on the surface of LED chip is picked up by the fiber probe of NSOM system. The system was made by ourselves, and the distance between the probe and the surface is controlled by shear force feedback control method using tuning fork, where lock-in amplifier was used for noise reduction and for dithering the probe.

Noise-robust Phase Gradient Retrieval Formulation for Phase-shifting Interferometry

Modification of the phase gradient formulation is proposed in order to make phase retrieval less susceptible to noise. The modified formulation is derived from separation of the phase terms and the intensity modulation terms of interferograms, and subsequent differentiation to reduce the noise-induced error of the phase gradient vector. Its performance is evaluated and compared to that of the conventional formulation, and noise-robust nature is confirmed.

Analysis of photonic crystal filter structures and its application : Wavelength demultiplexer

Based on photonic crystal optical filters, ultra compact wavelength demultiplexer for splitting 1.31/1.55 mum wavelength signals is newly proposed. The device characteristics are analyzed and optimally designed by using the FDTD method.

Modified Formulation of Phase Gradient for Noise-Immune Phase Retrieval in Phase-Shifting Interferometry

For retrieving phase information from interferograms in phase-shifting interferometry, the method of finding phase gradients is newly proposed, and it was confirmed to have the noise-immune performance superior to those of conventional methods.