JEOS:RP - Journal of the European Optical Society Rapid publications
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Laser Doppler imaging of microflow
Get PDFWe report results obtained with a wide-field laser Doppler detection
scheme used to perform laser Doppler anemometry and imaging of
particle-seeded microflow. The optical field carrying the local
scatterers (particles) dynamic state, as a consequence of momentum transfer at each scattering event, is analyzed in the temporal frequencies domain. The setup is based on heterodyne digital holography, which is used to map the scattered field in the object plane at a tunable frequency with a multipixel detector. We show that wide-field heterodyne laser Doppler imaging can be used for quantitative microflow diagnosis; in the presented study, maps of the first-order moment of the Doppler frequency shift are used as a quantitative and directional estimator of the Doppler signature of particles velocity
Coherence effects in propagation through photonic crystals
Get PDFoai:ojs.pkp.sfu.ca:article/51We have analytically studied how a partially coherent quasi plane wave is affected by a photonic crystal structure including a grating. The analysis is presented for spatial and temporal cases showing the possibility to determine the coherence characteristics of the pulse
Generation of squeezing in higher order Hermite-Gaussian modes with an optical parametric amplifier
Get PDFWe demonstrate quantum correlations in the transverse plane of continuous wave light beams by producing -4.0 dB, -2.6 dB and -1.5 dB of squeezing in the TEM_{00}, TEM_{10} and TEM_{20} Hermite-Gauss modes with an optical parametric amplifier, respectively. This has potential applications in quantum information networking, enabling parallel quantum information processing. We describe the setup for the generation of squeezing and analyse the effects of various experimental issues such as mode overlap between pump and seed and nonlinear losses
Efficient optimization of hollow-core photonic crystal fiber design using the finite-element method
Get PDFWe employ a finite-element (FE) solver with adaptive grid refinement to model hollow-core photonic crystal fibers (HC-PCFs) whose core is formed from 19 omitted cladding unit cells. We optimize the complete fiber geometry for minimal field intensity at material/air interfaces, which indicates low loss and high damage threshold, using multidimensional optimization. Our approach has very high numerical efficiency and accuracy, and we confirm that the FE-method is particularly well suited to model HC-PCFs
Wide-band optical field concentrator for low-index core propagation
Get PDFWe propose a novel chirped structure consisting of a low index polymer core bounded by modulated multilayer claddings, to realize an optical field concentrator with virtually zero propagation losses in a wide spectral range, independent of wave polarization. In spite of the absence of the total internal reflection mechanism, properly designed multilayer claddings ensure the achievement of unitary transmittance in a wide spectral range, including the widely used wavelengths for optical communications. Several cladding geometries obtained by varying the thicknesses of the cladding layers are reported and discussed
Plasmonic Marangoni forces
Get PDFLocalized surface-tension-driven forces (microscale Marangoni effect) caused by a temperature inhomogeneity from the decay of optically excited surface plasmons into phonons have been engaged to the actuation of adsorbed and applied liquid on a thin metal film. Microfluidic operations of transport, separation, mixing and sorting have been experimentally and theoretically demonstrated using this all-optical modulation scheme
Invertebrate superposition eyes-structures that behave like metamaterial with negative refractive index
Get PDFThe superposition eyes of lobsters and moths are described with the geometrical optics for a refractive surface between two media, where the refractive index of the image space is negative. Consequently, the eye power and the object focal length are negative, whereas the image focal length is positive. The F-number is also negative, but the sign is irrelevant for calculations of the light sensitivity, because that depends on F2. The angular magnifications necessary for perfect focusing calculated for the superposition eyes of dung beetles diverge from measured values, and therefore the focus is distributed
Photonic crystal fibres: mapping Maxwell's equations onto a Schrödinger equation eigenvalue problem
Get PDFWe consider photonic crystal fibres (PCFs) made from arbitrary base materials and introduce a short-wavelength approximation which allows for a mapping of the Maxwell's equations onto a dimensionless eigenvalue equations which has the form of the Schröding equation in quantum mechanics. The mapping allows for an entire analytical solution of the dispersion problem which is in qualitative agreement with plane-wave simulations of the Maxwell's equations for large-mode area PCFs. We offer a new angle on the foundation of the endlessly single-mode property and show that PCFs are endlessly single mode for a normalized air-hole diameter smaller than ~042, independently of the base aterial. Finally, we show how the group-velocity dispersion relates simply to the geometry of the photonic crystal cladding
Polarization insensitive blazed diffraction gratings
Get PDFGratings insensitive to light polarization may be useful in many areas of optical engineering, particularly in light demultiplexing application. We study different kinds of binary gratings able to present reflected efficiencies higher than 98% in the –1st order. These are metallic gratings, dielectric gratings deposited on a metallic substrate, total internal reflection gratings and gratings lying on a dielectric multilayer. We study each configuration with respect to manufacturing constraints and optical performances to conclude by providing the most suitable design
Passive introduction of carrier fringes in real-time photorefractive interferometers for single interferogram analysis
Get PDFWe propose a new technique to introduce carrier fringes in an holographic interferometric set-up for deformation or vibration analyses. This technique makes use of the anisotropic diffraction processes of photorefractive crystals. The main advantage of the proposed technique is that it just involves static components, no moving parts or active components are required. This technique is demonstrated in a real-time interferometric set-up operating at the wavelength of 1.06 µm and with a GaAs photorefractive crystal as the holographic medium