Search results for "photonics"
showing 10 items of 802 documents
Absolute Chiral Sensing in Dielectric Metasurfaces Using Signal Reversals.
2020
Sensing molecular chirality at the nanoscale has been a long-standing challenge due to the inherently weak nature of chiroptical signals, and nanophotonic approaches have proven fruitful in accessing these signals. However, in most cases, absolute chiral sensing of the total chiral refractive index has not been possible, while the strong inherent signals from the nanostructures themselves obscure the weak chiroptical signals. Here, we propose a dielectric metamaterial system that overcomes these limitations and allows for absolute measurements of the total chirality, and the possibility for a crucial signal reversal that enables chirality measurements without the need for sample removal. As…
The interaction of surface plasmon polaritons with a silver film edge.
2001
A prism coupling arrangement is used to excite surface plasmons at the surface of a thin silver film and a photon scanning tunnelling microscope is used to detect the evanescent field above the silver surface. Excitation of the silver/air mode of interest is performed at lambda1 = 632.8 nm using a tightly focused beam, while the control of the tip is effected by exciting a counter-propagating surface plasmon field at a different wavelength, lambda2 = 543.5 nm, using an unfocused beam covering a macroscopic area. Propagation of the red surface plasmon is evidenced by an exponential tail extending away from the launch site, but this feature is abruptly truncated if the surface plasmon encount…
Single molecules probe local density of modes (LDOS) around photonic nanostructures
2008
International audience; According to Fermi's golden rule, the fluorescence decay rate is directly proportional to the projected local density of photonic modes (LDOS) at the molecule location. The relevant LDOS depends on the molecule orientation. In this paper, the direct measurement of the fluorescence lifetime near gold dot photonic structures is investigated and compared to calculated LDOS. Detailed analysis of the decay channels is presented on the basis of numerical simulations.
Light field propagation by metal micro- and nanostructures
2001
The ability to sustain plasmon oscillations gives rise to unique properties of metal nanostructures, which can be exploited for the controlled manipulation of light fields on the nanoscale. In this context we investigate electromagnetic coupling effects within lithographically produced ensembles of gold nanoparticles with a photon scanning tunnelling microscope. To provide an interface between these nano-optical devices and classical far-field optics, we investigate surface plasmon propagation on microstructured metal thin films.
Gas-phase supersaturation effects on morphology properties of ZnO nano and microstructures grown by PVT
2016
A systematic study of the morphology evolution of ZnO nanostructures grown by physical vapour transport was carried out. The evolution of the shape with the growth time is shown to depend on the different gas-phase supersaturation and temperature conditions encountered in the crystallization zone of the tube furnace. The observed morphology transitions are discussed, and a growth model for ZnO nanostructures is given.
Multiple-plane image formation by Walsh zone plates.
2018
[EN] A radial Walsh filter is a phase binary diffractive optical element characterized by a set of concentric rings that take the phase values 0 or ¿, corresponding to the values + 1 or ¿1 of a given radial Walsh function. Therefore, a Walsh filter can be re-interpreted as an aperiodic multifocal zone plate, capable to produce images of multiple planes simultaneously in a single output plane of an image forming system. In this paper, we experimentally demonstrate for the first time the focusing capabilities of these structures. Additionally, we report the first achievement of images of multiple-plane objects in a single image plane with these aperiodic diffractive lenses.
Image quality enhancement for skin cancer optical diagnostics
2017
The research presents image quality analysis and enhancement proposals in biophotonic area. The sources of image problems are reviewed and analyzed. The problems with most impact in biophotonic area are analyzed in terms of specific biophotonic task – skin cancer diagnostics. The results point out that main problem for skin cancer analysis is the skin illumination problems. Since it is often not possible to prevent illumination problems, the paper proposes image post processing algorithm – low frequency filtering. Practical results show diagnostic results improvement after using proposed filter. Along that, filter do not reduces diagnostic results’ quality for images without illumination de…
Gold Nanoparticle Growth Monitored in situ Using a Novel Fast Optical Single-Particle Spectroscopy Method
2007
Size- and shape-dependent optical properties of gold nanorods allow monitoring their growth using a novel fast single-particle spectroscopy (fastSPS) method. FastSPS uses a spatially addressable electronic shutter based on a liquid crystal device to investigate particles randomly deposited on a substrate, orders of magnitude faster than other techniques. We use fastSPS to observe nanoparticle growth in situ on a single-particle level and extract quantitative data on nanoparticle growth.
Three-dimensional imaging system with both improved lateral resolution and depth of field considering non-uniform system parameters
2018
In this paper, we propose a new 3D passive image sensing and visualization technique to improve lateral resolution and depth of field (DoF) of integral imaging simultaneously. There is a resolution trade-off between lateral resolution and DoF in integral imaging. To overcome this issue, a large aperture and a small aperture can be used to record the elemental images to reduce the diffraction effect and extend the DoF, respectively. Therefore, in this paper, we utilize these two pickup concepts with a non-uniform camera array. To show the feasibility of our proposed method, we implement an optical experiment. For comparison in details, we calculate the peak signal-to-noise ratio (PSNR) as th…
Joint Distribution of Polarization-Multiplexed UWB and WiMAX Radio in PON
2009
[EN] In this paper, the feasibility of the joint distribution of ultra-wideband (UWB) and WIMAX wireless using polarization multiplexing as a coexistence technique is proposed and experimentally demonstrated within the framework of passive optical networks (PON). Four single- and orthogonal-polarization multiplexing schemes are studied targeting to reduce the mutual interference when UWB and WiMAX are distributed jointly through standard single-mode fiber (SSMF) without transmission impairments compensation techniques and amplification. Experimental results indicate successful transmission up to 25 km, in SSMF exceeding the range in typical PON deployments. The radio link penalty introduced…