• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.438-443
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• 2010

In this paper, behaviors of photonic crystal (PC) radiative structures and antenna arrays have been compared for two types of uniform and binomial excitations. Appropriate duality has been shown between them. These results can be generalized to other types of excitation and arrangement of photonic crystal radiative arrays such as linear, planar and circular arrays of three dimensional (3D) photonic crystal termination resonators. Using these results in designing photonic circuits has some advantages for shaping a particular radiative beam at the photonic crystal exit, for instance reducing the divergence angle of the main lobe in order to enhance the directivity, for better coupling, or for splitting the emitted beam, for dividing the output beam to the next devices in photonic integrated circuits (PIC). For analysis and simulation of the photonic crystal structures, the finite difference time domain (FDTD) method has been employed.

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.308-309
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• 2004

• Current Optics and Photonics
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• v.5 no.6
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• pp.606-616
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• 2021

A photonic integrated interferometric imaging system possesses the characteristics of small-scale, low weight, low power consumption, and better image quality. It has potential application for replacing conventional large space telescopes. In this paper, the principle of photonic integrated interferometric imaging is investigated. A novel lenslet array arrangement and lenslet pairing approach are proposed, which are helpful in improving spatial frequency coverage. For the novel lenslet array arrangement, two short interference arms were evenly distributed between two adjacent long interference arms. Each lenslet in the array would be paired twice through the novel lenslet pairing approach. Moreover, the image reconstruction model for optical interferometric imaging based on compressed sensing was established. Image simulation results show that the peak signal to noise ratio (PSNR) of the reconstructed image based on compressive sensing is about 10 dB higher than that of the direct restored image. Meanwhile, the normalized mean square error (NMSE) of the direct restored image is approximately 0.38 higher than that of the reconstructed image. Structural similarity index measure (SSIM) of the reconstructed image based on compressed sensing is about 0.33 higher than that of the direct restored image. The increased spatial frequency coverage and image reconstruction approach jointly contribute to better image quality of the photonic integrated interferometric imaging system.

• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.283-288
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• 2011

In this study, a wide-band photonic crystal Y-splitter for TE modes is proposed. A triangular lattice of air holes etched in a GaAs slab is used as the platform. In order to numerically analyze the structures, plane wave expansion (PWE) and finite difference time domain (FDTD) methods are used. In comparison with the structures reported in the literature, the proposed topology has a less complexity while it provides more than 100nm bandwidth. The simplicity of the design, its high transmission ratio and its wide bandwidth makes it a suitable choice for the implementation of photonic crystal integrated circuits.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.6
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• pp.515-521
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• 2003

There are now many theoretical investigations and real manufactures for numerous applications of photonic crystals (PCs) associated with photonic band gap and photonic integrated circuits. However, there are some difficulties to design and fabricate the desired pattern quality. It is not easy to satisfy accurate critical dimension (CD) for patterns with arbitrary shapes and pitch sizes aligned in various directions. In this work, we report the optimum conditions to better fabricate and design, and greatly improve pattern quality in delineating two-dimensional (2D) PCs in the nanometer range using single- step e-beam lithography system with conventional exposure mode.

• Journal of the Optical Society of Korea
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• v.15 no.2
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• pp.187-195
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• 2011

We have designed two photonic crystal waveguide (PCW) structures with output focused beams in order to achieve more coupling between photonic devices and decrease the mismatch losses in photonic integrated circuits. PCW with coupled resonator optical waveguide (CROW) termination has been optimized by both one dimensional (1D) and seven dimensional (7D) particle swarm optimization (PSO) algorithms by evaluating the fitness function by the finite difference time domain (FDTD) method. The 1D and 7D-optimizations caused the factors of 2.79 and 3.875 improvements in intensity of the main lobe compared to the non-optimized structure, whereas the FWHM in 7D-optimized structure was increased, unlike the 1D case. It has also been shown that the increment of focusing causes decrement of the bandwidth.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.196-196
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• 2012

Graphene, two-dimensional one-atom-thick planar sheet of carbon atoms densely packed in a honeycomb crystal lattice, has grabbled appreciable attention due to its extraordinary mechanical, thermal, electrical, and optical properties. Based on the graphene's high carrier mobility, high frequency graphene field effect transistors have been developed. Graphene is useful for photonic components as well as for the applications in electronic devices. Graphene's unique optical properties allowed us to develop ultra wide-bandwidth optical modulator, photo-detector, and broadband polarizer. Graphene can support SPP-like surface wave because it is considered as a two-dimensional metal-like systems. The SPPs are associated with the coupling between collective oscillation of free electrons in the metal and electromagnetic waves. The charged free carriers in the graphene contribute to support the surface waves at the graphene-dielectric interface by coupling to the electromagnetic wave. In addition, graphene can control the surface waves because its charge carrier density is tunable by means of a chemical doping method, varying the Fermi level by applying gate bias voltage, and/or applying magnetic field. As an extended application of graphene in photonics, we investigated the characteristics of the graphene-based plasmonic waveguide for optical signal transmission. The graphene strips embedded in a dielectric are served as a high-frequency optical signal guiding medium. The TM polarization wave is transmitted 6 mm-long graphene waveguide with the averaged extinction ratio of 19 dB at the telecom wavelength of $1.31{\mu}m$. 2.5 Gbps data transmission was successfully accomplished with the graphene waveguide. Based on these experimental results, we concluded that the graphene-based plasmonic waveguide can be exploited further for development of next-generation integrated photonic circuits on a chip.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.268-269
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• 2000

We demonstrate a polarization insensitive waveguide filter using quantum well intermixing(QWI). The bandgap of epitaxial layer is modified from 1.55${\mu}{\textrm}{m}$ to 1.40${\mu}{\textrm}{m}$ using QWI and a Bragg grating filter is demonstrated using electron beam lithography technology. The fabricated waveguide filter has a 70% reflection efficiency and a 1.46nm filter bandwidth. Furthermore polarization insensitive transmission characteristics are observed. The device can be applied to photonic integrated circuits(PIC).

• Vacuum Magazine
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• v.4 no.3
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• pp.16-20
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• 2017

Graphene has emerged as a promising material for optoelectronic applications including as ultrafast and broadband photodetector, optical modulator, and nonlinear photonic devices. Graphene based devices have shown the feasibility of ultrafast signal processing for required for photonic integrated circuits. However, on-chip monolithic nanoscale light source has remained challenges. Graphene's high current density, thermal stability, low heat capacity and non-equilibrium of electron and lattice temperature properties suggest that graphene as promising thermal light source. Early efforts showed infrared thermal radiation from substrate supported graphene device, with temperature limited due to significant cooling to substrate. The recent demonstration of bright visible light emission from suspended graphene achieve temperature up to ~3000 K and increase efficiency by reducing the heat dissipation and electron scattering. The world's thinnest graphene light source provides a promising path for on-chip light source for optical communication and next-generation display module.

• Current Optics and Photonics
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• v.2 no.6
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• pp.576-581
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• 2018

A new approach for identification of a microwave frequency using an integrated optical waveguide chip, combined with a phase modulator (PM) and two microring resonators (MRRs), is proposed, theoretically deduced, and verified. By wavelength tuning to set the PM under the condition of a double side band (DSB), the measurement range can be started from the dc component, and the measurement range and response slope can be adjusted by designing the radius and transmission coefficient of the MRR. Simulations reveal that the amplitude comparison function (ACF) has a monotonic relationship from dc to 32.5 GHz, with a response slope of 5.15 dB under conditions of DSB modulation, when the radius values, transmission coefficients, and the loss factors are designed respectively as $R_1=400{\mu}m$, $R_2=600{\mu}m$, $t_1=t_2=0.63$, and ${\gamma}_1={\gamma}_2=0.66$. Theoretical calculations and simulation results both indicate that this new approach has the potential to be used for measuring microwave frequencies, with the advantages of compact structure and superior reconfigurability.