JEOS:RP - Journal of the European Optical Society Rapid publications
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Magnetite nanoparticles for biosensor model based on bacteria fluorescence
Get PDFFluorescence emission of pyoverdine – the siderophore synthesized by iron scavenger bacteria - was studied using in vitro cultures of Pseudomonas aeruginosa with the aim to design a biosensor system for liquid sample iron loading. Diluted suspensions of colloidal magnetite nanoparticles were supplied in the culture medium (10 microl/l and 100 microl/l) to simulate magnetic loading with iron oxides of either environmental waters or human body fluids. The electromagnetic exposure to radiofrequency waves of bacterial samples grown in the presence of magnetic nanoparticles was also carried out. Cell density diminution but fluorescence stimulation following 10 microl/l ferrofluid addition and simultaneous exposure to radiofrequency waves was evidenced. The inhibitory influence of 100 microl/l ferrofluid combined with RF exposure was evidenced by fluorescence data. Mathematical model was proposed to approach quantitatively the dynamics of cell density and fluorescence emission in relation with the consumption of magnetite nanoparticle supplied medium. The biosensor scheme was shaped based on the response to iron loading of bacterial sample fluorescence
Real-time terahertz imaging for art conservation science
Get PDFA new real-time terahertz imaging system has been developed by using a quantum cascade laser source and a microbolometer focal plane detector array. The application to non-invasive analyses of cultural heritage is demonstrated with an oil paint specimen. The experimental results suggested that the terahertz imaging system can identify materials based on a spectral database with a spatial resolution of about 300 μm. The transmission imaging indicated the difference between natural and artificial ultramarine pigments. Since the size of the system is similar to a common portable infrared camera, it can be used at the place where the object is located, such as museums, and can contribute to conservation activities, such as drying process monitoring. This real-time, small, non-invasive terahertz imaging system can be used in various fundamental research fields and practical industries
Analysis and optimization of the stereo-system with a four-mirror adapter
Get PDFStereo imaging is becoming an important diagnostic tool in many practical applications throughout the industries. In the diagnostic procedure two views are used to provide in-depth information of the observing object. The conventional two-synchronized-camera systems, used in most applications, pose difficulty to people new to the applications, especially when off-the-shelf cameras have to be used. In this article, several commonly used single camera stereo systems are reviewed and studied. The stereo system with a four-mirror adapter in particular is analyzed, whereafter an improvement is made to achieve the maximum field of view (FOV) of the stereo system with the four-mirror adapter
High speed partial Stokes imaging using a ferroelectric liquid crystal modulator
Get PDFThis paper describes the implementation of an imaging polarimeter using a single ferroelectric liquid crystal light modulator. It provides partial imaging Stokes information at 234 Hz, much faster than polarimeters using nematic light modulators. This information is obtained for dynamic scenes in reflection or transmission. Partial Stokes information contains the first three Stokes parameters. With this information, imaging of the linear degree of polarization and of the angle of polarization can be obtained and imaging linear depolarization can be quantified
Nanostructure design for surface-enhanced Raman spectroscopy -- prospects and limits
Get PDFSurface-enhanced Raman spectroscopy (SERS) allows single-molecule detection due to the strong field localization occurring at sharp bends or kinks of the metal-vacuum interface. An important question concerns the limits of the signal enhancement that can be achieved via a judicious design of the surface. By using a specific example of a technologically realizable nanopatterned surface, we demonstrate that while very high enhancement factors (~10^12) can be found for an ideal surface, these are unlikely to be achieved in laboratory samples, because even a minute, inevitable rounding-off strongly suppresses the enhancement, as well as shifts the optimal frequency. Our simulations indicate that the geometric enhancement factors are unlikely to exceed ~10^8 for real samples, and that it is necessary to consider the geometric uncertainty to reliably predict the frequency for maximum enhancement
Leaky modes of a left-handed slab
Get PDFUsing complex plane analysis we show that left-handed slab may support either leaky slab waves, which are backward because of negative refraction, or leaky surface waves, which are backward or forward depending on the propagation direction of the surface wave itself. Moreover, there is a general connection between the reflection coefficient of the left-handed slab and the one of the corresponding right-handed slab (with opposite permittivity and permeability) so that leaky slab modes are excited for the same angle of incidence of the impinging beam for both structures. Many negative giant lateral shifts can be explained by the excitation of these leaky modes
Polarization conversion with a photonic crystal slab
Get PDFWe show that a photonic crystal slab can enable efficient polarization conversion. Two mechanisms are identiï¬ed. The ï¬rst mechanism relies on the anisotropy of the bulk properties of the metamaterial and is
mediated by interferences. The second mechanism is due to the resonant excitation of leaky surface waves at the interface of the photonic crystal. The latter is analogous to the polarization conversion by excitation of
surface plasmons on a metallic grating. This is another example of the possibility of mimicking plasmonics with photonic crystals
Light propagation in atomic Mott Insulators
Get PDFWe study radiation-matter interaction in a system of ultracold atoms trapped in an optical lattice in a Mott insulator phase. We develop a fully general quantum model, and we perform calculations for a one-dimensional geometry at normal incidence. Both two- and three-level atomic configurations are studied. The polariton dispersion and the reflectivity spectra are characterized in the different regimes, for both semi-infinite and finite-size geometries. We apply this model to propose a photon energy lifter experiment: a device which is able to shift the carrier frequency of a slowly travelling wavepacket without affecting the pulse shape nor its coherence
Degree of polarization and quantum-mechanical purity
Get PDFThe purity parameter is used in quantum mechanics to discriminate
pure states from mixed states. We employ this concept to define a
degree of polarization for general, three-dimensional, classical
random electric fields. Our approach leads to a result that is
identical with a recent definition obtained by a decomposition of
the polarization matrix in terms of the Gell-Mann matrices. We
also give an expression for this degree of polarization based on
the constituent two-dimensional subsystems
Polarization conversion by dielectric subwavelength gratings in conical mounting
Get PDFSubwavelength dielectric gratings are examined in total-internal-reflection configuration. It is demonstrated experimentally that such elements, fabricated in TiO2, can perform full polarization conversion from incident TE to TM with nearly 100% efficiency. The dependence of the polarization conversion on the angle of incidence is analyzed. Rigorous diffraction theory is used to cross check the experimental results