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A one-dimensional photonic crystal with a superconducting defect layer
Lyubchanskii, I L,Dadoenkova, N N,Zabolotin, A E,Lee, Y P,Rasing, Th Institute of Physics Publishing in association wit 2009 Journal of optics A, Pure and applied optics Vol.11 No.11
<P>A one-dimensional dielectric photonic crystal with a complex defect layer, consisting of ultrathin superconducting and dielectric sublayers, is theoretically studied. It is shown that the position of the defect mode and the transmittivity at the defect mode frequency strongly depend on the thickness of the superconducting sublayer as well as on the temperature.</P>
Choi, Hyoung-Gyu,Kee, Chul-Sik,Park, Hae Yong,Kim, Jae-Eun Institute of Physics Publishing in association wit 2009 Journal of optics A, Pure and applied optics Vol.11 No.12
<P>We have numerically investigated supercontinuum generation in photonic crystal fibers with zero-dispersion wavelengths in the vicinity of 800 nm by using an input pulse with a peak power of about 20 kW and a width of about 10 fs. The effects of fiber dispersion and the input pulse parameters on the generated optical spectra are quantitatively analyzed. The propagation length necessary for the generation of a soliton in the anomalous dispersion region is found to depend on the zero-dispersion wavelength of a fiber. For the generation of a sufficiently broad spectrum, the photonic crystal fiber should be longer than the soliton-generation length. In addition, a spectral recoil effect appears when a solitary wave splits the dispersive wave into two parts.</P>
Preparation of ferroelectric nanoparticles for their use in liquid crystalline colloids
Atkuri, H,Cook, G,Evans, D R,Cheon, C-I,Glushchenko, A,Reshetnyak, V,Reznikov, Yu,West, J,Zhang, K Institute of Physics Publishing in association wit 2009 Journal of optics A, Pure and applied optics Vol.11 No.2
<P>In this paper we summarize our many years of experience in the preparation and optimization of stable colloids of ferroelectric nanoparticles dispersed in an isotropic carrier and in a liquid crystal host. The colloids are of interest for use in electro-optic devices, photorefractive hybrids and nonlinear optical elements. We also outline some of the most interesting features the nanoparticles bring to liquid crystals, along with the potential of these relatively new colloids.</P>
Ahn, Yu-Hwan,Shanmugam, Palanisamy Institute of Physics Publishing in association wit 2007 Journal of optics A, Pure and applied optics Vol.9 No.4
<P>This paper presents an analysis of several in-water algorithms developed using a large number of bio-optical data collected in Korean and neighbouring ocean waters. The upward and downward light fields measured in these waters were normalized to provide remote sensing reflectance (<I>R</I><SUB>rs</SUB>) from which the variations in sun-induced chlorophyll-a (Chl-a) fluorescence from phytoplankton biomass were analysed and the fluorescence line height (ΔFlu) was measured using a baseline method. ΔFlu measurements were related to <I>in situ</I> Chl-a concentrations (used as an index for quantifying the algal material) to obtain the ΔFlu(681), ΔFlu(688) and ΔFlu<SUB>(area)</SUB> algorithms, which were compared with those from standard spectral ratios of the remote sensing reflectance, <I>R</I><SUB>rs</SUB>(444)/<I>R</I><SUB>rs</SUB>(554) and <I>R</I><SUB>rs</SUB>(490)/<I>R</I><SUB>rs</SUB>(554). Comparison revealed the correlation coefficients (<I>r</I><SUP>2</SUP>) 0.88–0.90 for the fluorescence algorithms and 0.79–0.85 for the spectral ratios algorithms. A validation analysis using a new data set illustrated the merits of these algorithms in Case II waters. Fluorescence-based algorithms tended to reproduce <I>in situ</I> Chl-a concentrations (from 0.1 to 82?mg?m<SUP>−3</SUP>), whereas standard spectral ratios algorithms gave inconsistent estimates, probably caused by the interference of inorganic sediment and dissolved organic matter in these waters. For measurements of the sun-induced Chl-a fluorescence signal in coastal waters, this study discusses the requirements and provides the optimal channels to be adopted in the design of the new generation ocean colour sensors planned in the near future.</P>
Analysis of the electro-optic measurement of an electron beam with new refractive indices
Parc, Yong Woon,Ko, In Soo Institute of Physics Publishing in association wit 2009 Journal of optics A, Pure and applied optics Vol.11 No.10
<P>Electro-optic sampling (EOS) is a promising method of measuring the electron bunch length and arrival time nondestructively. When an electric field is applied to the EO crystal, the EO crystal shows birefringence which is described by an ellipsoid of refractive indices. The ellipsoid can be expressed with the principal axes associated with the crystallographic axes. If a linearly polarized laser is passing through the EO crystal with external electric field, the polarization of the laser is modulated elliptically or even circularly. The polarization modulation of the laser probe beam should be expressed in terms of the relative phase shift between the decomposed vectors of the laser. Conventional analysis assumes that the polarization direction of the laser probe beam is to set to be at an angle of 45° with the principal axes. Only the principal refractive indices have been used until now with this assumption. However, if the position of the electron beam is changed in experiments, the electric field applied to the EO crystal is also changed. Thus, the directions of the principal axes of the isotropic crystal are also changed. The principal axes do not make an angle of 45° anymore with the fixed polarization vector of the laser probe beam in this situation. New refractive indices are needed to explain the experimental result with such deviation properly. In our work, new refractive indices are derived and simulation studies are carried out with the pulse propagation method, which utilizes the Fourier transform to investigate the evolution of the electromagnetic pulse inside the EO crystal. Experimental results are in good agreement with the prediction from the simulation with newly derived refractive indices.</P>
A glass reflowed microlens array on a Si substrate with rectangular through-holes
Lee, Sung-Kil,Kim, Man-Geun,Jo, Kyoung-Woo,Shin, Sang-Mo,Lee, Jong-Hyun Institute of Physics Publishing in association wit 2008 Journal of optics A, Pure and applied optics Vol.10 No.4
<P>A thermally reflowed glass microlens array was fabricated on a Si substrate. Glass lenses are more durable and scratch-resistant than plastic lenses made by the same, simple thermal reflow process. The microlens was designed using the ray tracing technique and optimized by controlling the nominal diameter and height of glass cylinders. The glass cylinders were formed by wet etching a glass plate in a HF (49%) solution and reflowed to form a semi-spherical lens shape at 850 °C (glass transition temperature <I>T</I><SUB>g</SUB> = 820 °C) for 20 min in a furnace. Then, the Si substrate was etched in a TMAH (5%) solution to make rectangular through-holes underneath the microlens array for high optical transmission. The profile of the fabricated microlens was measured with a confocal microscope, and its optical characteristics (lens size, beam radius and focal length) were evaluated with a 633 nm laser diode beam. The experimental beam waist (minimum beam radius) at the focal point of 1000 µm was 8 µm, which was in good agreement with a calculated value. The results show that the microlens array can be used in a broad wavelength range from UV to the IR region.</P>