JEOS:RP - Journal of the European Optical Society Rapid publications
Not a member yet
545 research outputs found
Sort by
Phase retrieval between overlapping orders in coherent Fourier scatterometry using scanning
Get PDFNon-interferometric phase retrieval from the intensity measurements in Coherent Fourier Scatterometry (CFS) is presented using a scanningfocused spot. Formulae to determine the state of polarization of the scattered light and to retrieve the phase difference between overlappingscattered orders are given. The scattered far field is rigorously computed and the functionality of the method is proved with experimentalresults
Modeling of the light transfer in a water column polluted with oil suspension
Get PDFThe radiance field in oil-polluted seawater determined at various depths for the central band of the light spectrum (547 nm) is considered. In the aquatic model, a flat sea surface, a cloud-free sky and selected inherent optical properties (IOPs) of natural seawater and oil-in-water emulsion are taken into account. The representative results of Monte Carlo photon trace simulations are presented for the directional radiance distribution (L), the directional distribution of the radiance reflectance (R_L) and the intensity of downward and upward irradiance (E)
A direct comparison between a MEMS deformable mirror and a liquid crystal spatial light modulator in signal-based wavefront sensing
Get PDFAberrations degrade the performance of optical systems in terms of resolution and signal-to-noise ratio. This work explores the feasibility of a signal-based wavefront sensor, which employs a search algorithm to estimate Zernike coefficients of given aberrations. The search algorithm was supported by Gaussian interpolation. The performance of two different reflective wavefront correctors, a deformable mirror and a spatial light modulator in signal-based wavefront sensing, was compared under identical conditions. The aberrations were introduced by using another identical high resolution reflecting spatial light modulator. The performance was quantified using the Strehl ratio, which was estimated from simultaneously acquired Hartmann-Shack measurements of Zernike coefficients. We find that the spatial light modulator can be a good alternative to the deformable mirror in terms of dynamic range and sensitivity, when speed is not a limiting factor. Distinct advantages of the spatial light modulator are high number of pixels and a larger active area
Spatial profiling of optical gain for optimizing lasing in plasmonic nano-lasers
Get PDFDesign of cylindrical metal-clad semiconductor nano-lasers is undertaken. Specific attention is given to determining the modal gain instructures supporting TM01 Surface Plasmon Polarition (SPP) modes. For representative structures it is indicated that cavity lengths oforder 100 μm enable lasing action. In comparison structures supporting TE01 core-confined modes having cavity lengths of order 10 μm may sustain lasing. The analysis methodology adopted offers means to affect the design of candidate semiconductor lasers for bespokeapplications
Optical spectrum behaviour of a coupled laser system under chaotic synchronization conditions
Get PDFSynchronization characteristics of two bidirectionally coupled semiconductor lasers, one operating in a chaotic regime with low-frequencyfluctuations and the other with free laser beam emission, were experimentally investigated. The chaotic synchronization regimes and opticalspectral behavior of the coupled system were analyzed with respect to the optical spectra emitted initially by the two uncoupled lasersoperated under the same feedback conditions. It was observed that the number of synchronization regimes that can be obtained and theirstability depend on the similarity of spectral structures of the uncoupled lasers emissions. The dominant active laser modes of the coupledsystem emission coincide with the laser modes of the one or both uncoupled laser emissions, depending on the operating synchronizationregime. We have associated changes in the optical spectrum of the coupled system with the synchronization regimes. The repartition ofpower between the active modes of a coupled system allows identification of the synchronization regime
Modelling the influence of oil content on optical properties of seawater in the Baltic Sea
Get PDFThe accuracy and correct interpretation of optical parameters of seawater depend on the complete information osn the interactions between seawater components and the light field. Among components influencing the radiative transfer, the droplets of oil can cause overor underestimation of modelled and measured optical quantities, especially in closed seas and coastal zones. Oil content in the Baltic Sea varies from several ppb in the open sea to several ppm in estuaries or ship routes. Oil droplets become additional absorbents and attenuators in seawater causing changes in apparent optical properties. These changes can potentially enable remote optical detection of oil-in-water emulsion in visible bands. To demonstrate potential possibilities of such optical remote sensing, a study of inherent optical properties of two types of crude oil emulsion was conducted, i.e. high absorptive and strongly scattering Romashkino, and low absorptive and weakly scattering Petrobaltic. First, the calculations of spectral absorption and scattering coefficients as well as scattering phase functions for oil emulsions were performed on the basis of Lorentz-Mie theory for two different oil droplets size distributions corresponding to a fresh and 14-days aged emulsions. Next, radiative transfer theory was applied to evaluate the contribution of oil emulsion to remote sensing reflectance R_rs(λ). Presented system for radiative transfer simulation is based on Monte Carlo code and it involves optical tracing of virtual photons. The model was validated by comparison of R_rs(λ) simulated for natural seawater to R_rs(λ) from in situ measurements in Baltic Sea. The deviation did not exceed 10% for central visible wavelengths and stayed within 5% for short and long wavelengths. The light Petrobaltic crude oil in concentration of 1 ppm causes typically a 10-30% increase of Rrs while the heavy Romashkino reduces Rrs for 30-50%
High coupling efficiency to a low dispersion slow light-supporting photonic crystal waveguide
Get PDFIn this paper, we design a waveguide on photonic crystal slab for propagation of low-dispersion slow light. By shifting the air holes adjacent to the waveguide, we obtain a photonic crystal waveguide with a group index of 25 in 25 nm bandwidth which results in a group index bandwidth product of 0.366. To take the advantages of low dispersion slow light generated in this engineered waveguide, we next focus on low coupling efficiency limitation. A low group index coupler is proposed to increase the transmission of the light to the slow mode in the low dispersion bandwidth. By using the proposed coupler and adjusting the structural parameters, the coupling efficiency to low dispersion slow light is improved 11 dB compared to the transmission without the coupler
Photonic crystal electrode to be used in organic LED structures
Get PDFIn this work we report the possibility to obtain a high refractive index grid anode directly on the substrate surface by fabricating a relatively large-area photonic crystal (PC) structure using the combinations of electron beam lithography (EBL) and focused ion beam (FIB) techniques. The performance of the realized photonic crystal (PC) structure were enhanced by milling the ITO layer until the glass substrate and by removing the further refractive index jump between the PC and the substrate. The good properties of highly conductive poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), ensured a continuous path for the current and a high refractive index jump for the PC structure by filling the holes in the PC structure
Optical characterization of aminosilane-modified silicon dioxide surface for biosensing
Get PDFSilicon dioxide surfaces, functionalized by two aminosilane compounds (3-amino-propyl-triethoxysilane, APTES; 3-amino-propyl-dimethylethoxysilane, APDMES) both dissolved in different solvents (dry ethanol and toluene), have been investigated by standard techniques such as spectroscopic ellipsometry (SE), water contact angle (WCA), and atomic force microscopy (AFM). Silane thicknesses between 5 and 80 Ã… have been found, depending on deposition conditions; surface wettabilities change, accordingly. These organic-inorganic interfaces have also been modified by a cross-linker (bis-sulfosuccinimidyl suberate) in order to covalently bind a fluorescein labeled protein A. The amount of protein linked to functional surfaces has been quantified by SE and fluorescence microscopy. These results could be very useful in developing new platforms for optical biosensing
Coherent excitation of a nonlinear microcavity
Get PDFCoherent excitation of a nonlinear semiconductor microcavity is theoretically reported. It intends to counterbalance the frequency drift ofthe cavity resonance driven by the nonlinear refractive effects, which causes a limitation in the energy coupling efficiency of an input pulseinto the cavity resonance. We show that exciting such a nonlinear microcavity with tailored chirped pulses allows to maintain the benefit oflight localization and to further enhance light-matter interactions, opening the way to the realization of highly efficient nonlinear devices