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Invariant Imbedding Theory of Wave Propagation in Stratified Complex Media
Kihong Kim,Hanjo Lim 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
We review a generalized version of the invariant imbedding theory of wave propagation, which has been developed by us recently, in various kinds of stratified media. The main idea of the method is to transform the boundary value problem of the original wave equation into an equivalent initial value problem of coupled ordinary dierential equations. This allows an exact and very efficient numerical calculation of the re ection and the transmission coefficients and of the wave functions inside inhomogeneous media. We demonstrate the advantages of the method over other theoretical methods by applying it to several interesting cases. In the rst case, we apply the method to the propagation of electromagnetic waves in random dielectric media. Next, we give a short discussion of the application of our method to wave propagation in nonlinear inhomogeneous media. Finally, we discuss the generalization of the invariant imbedding method to cases where several coupled waves propagate in arbitrarily-inhomogeneous stratied media and apply it to electromagnetic wave propagation in layered chiral media. We review a generalized version of the invariant imbedding theory of wave propagation, which has been developed by us recently, in various kinds of stratified media. The main idea of the method is to transform the boundary value problem of the original wave equation into an equivalent initial value problem of coupled ordinary dierential equations. This allows an exact and very efficient numerical calculation of the re ection and the transmission coefficients and of the wave functions inside inhomogeneous media. We demonstrate the advantages of the method over other theoretical methods by applying it to several interesting cases. In the rst case, we apply the method to the propagation of electromagnetic waves in random dielectric media. Next, we give a short discussion of the application of our method to wave propagation in nonlinear inhomogeneous media. Finally, we discuss the generalization of the invariant imbedding method to cases where several coupled waves propagate in arbitrarily-inhomogeneous stratied media and apply it to electromagnetic wave propagation in layered chiral media.
Optimal Transparent One-Dimensional Metallo-Dielectric Photonic Crystal Structures
Chul-SiK Kee,Hanjo Lim,Kihong Kim 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.1
We theoretically investigated the optical transmission of ¯nite one-dimensional metallo-dielectric photonic crystals composed of Ag and ZnS layers. The transmission spectra strongly depend on the positions of the metal layers in the unit cell. The intensity and the bandwidth of the transmission increase when the Ag layer is closer to the center of the unit cell. The phenomena are due to the anti- re°ection coating eect caused by the outer dielectric layers. Optimal transparent metallo-dielectric photonic crystal structures can be useful in improving the performance of thin-¯lm devices, such as transparent heat mirrors and transparent electrodes.
In-Plane Multichannel Drop Filter Built in a Homogeneous Two-Dimensional Photonic Crystal
Young-Geun Roh,전헌수,Hanjo Lim,Sangin Kim,Sungjoon Yoon 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.2
We report on an experimental demonstration of a photonic crystal (PC)-based in-plane multichannel drop filter. On a homogeneous two-dimensional PC platform with a photonic bandgap in the microwave range (8 -- 11 GHz), we constructed a highly selective, efficient multichannel filter by using resonant cavities for drop frequency selection. A maximum drop selectivity of $\sim$20 dB was demonstrated while the resonance frequency width was as narrow as $\Delta$f $\sim$ 17 MHz. These results agree well with simulations based on the finite-difference time-domain method. We also obtained up to 2.2-fold improvement in drop efficiency by using a modified drop filter that incorporated a photon-recycling effect
Synthesis of GaAs/SiO2 Nanocomposite Films by Using an Alternating Sputtering Method
Sunghun Cho,Soonil Lee,Hanjo Lim 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.5
We fabricated GaAs/SiO$_2$ nanocomposite films at room temperature via the sequential sputtering of very thin layers of GaAs and SiO$_2$, which resulted in GaAs nanoparticles uniformly dispersed in a SiO$_2$ glass matrix. The high-resolution transmission electron microscopy (HRTEM) examination showed that the diameter of GaAs nanoparticles embedded in SiO$_2$ matrix depended on the nominal thickness of the GaAs layers. The blue-shift of the absorption edges gave not only the corroborating evidence for the systematic variation of the GaAs-nanoparticle size but also enabled us to estimate the diameter of GaAs nanoparticles quantitatively, which turned out to be consistent with the HRTEM observation. In addition to confirming the results of stylus, HRTEM, and Rutherford backscattering spectrometry (RBS) measurements, the analysis of variable-angle spectroscopic ellipsometry (VASE) spectra based on the effective medium theory revealed an interesting size-dependence of the complex refractive index of the GaAs nanoparticles.
Proposal for ideal 3-dB splitters-combiners in photonic crystals.
Kim, Sangin,Park, Ikmo,Lim, Hanjo Optical Society of America 2005 Optics letters Vol.30 No.3
<P>We propose a structure for ideal 3-dB splitters (1 x 2)-combiners (2 x 1) in photonic crystals. In photonic crystals, ideal 3-dB splitters based on a three-port system are achievable in principle, but it is impossible to achieve ideal 3-dB combiners based on the three-port system because there is no path for a loss, owing to strong confinement of photons. The proposed structure is based on a four-port system in which the concept of a microwave circuit, the so-called rat-race circuit is adopted. Design conditions for two-dimensional photonic-crystal-based rat-race circuits have been investigated by use of the coupled-mode theory in time. With the proposed structure, a 3-dB splitter-combiner has been designed. The performance of the device was numerically calculated by the finite-difference time-domain method.</P>
Lee, Sangjun,Kim, Sangin,Lim, Hanjo The Optical Society 2009 Optics express Vol.17 No.22
<P>We present improved characteristics of the curved plasmonic waveguide which consists of a thin metal stripe with asymmetric cladding layers. It is shown that in the proposed curved asymmetric plasmonic waveguides, a balance between a radiation due to bending and a radiation due to the asymmetric claddings allows a bending with a smaller radius curvature and a lower loss compared to the waveguide with symmetric claddings. At the same time, a symmetric metal stripe waveguide's typical trade-off between the bending characteristics and the propagation loss of a straight waveguide is relaxed with proper amount of asymmetry. With the proposed structure, a plasmonic waveguide bending whose radius is as small as 2 mm with a total loss of 1.8 dB/90 degrees is designed. Enhanced sensitivity to the surrounding medium and its application are discussed.</P>
Kim, Sangbum,Kim, Kihong,Rotermund, Fabian,Lim, Hanjo The Optical Society 2009 Optics express Vol.17 No.21
<P>A computational study of the second-harmonic generation in one-dimensional photonic crystals made of GaAs and AlAs with quadratic optical nonlinearity and material dispersion is presented. The computational approach uses a shooting method to solve nonlinear wave equations for coupled fundamental and second-harmonic fields and the invariant imbedding method to obtain the linear transmittance and group index spectra. The photonic crystal is built with an elementary cell consisting of four sublayers whose thicknesses are systematically varied. Doubly-resonant second harmonic generation with high conversion efficiency is achieved by choosing the geometrical parameters of the elementary cell optimally and controlling the band structure.</P>