Search results for "Optical"
showing 10 items of 7671 documents
Controlling ground-state rotational dynamics of molecules by shaped femtosecond laser pulses
2004
We report controlled excitation of ground-state rotational wave packet by pulse-shaping technique. The experiment is conducted in nitrogen $({\mathrm{N}}_{2})$ at room temperature and atmospheric pressure. A femtosecond laser pulse produces rotational coherences in the vibronic ground state of ${\mathrm{N}}_{2}$ through an impulsive Raman process. The laser pulse is tailored using a spatial light modulator producing spectral phase modulation. Periodic phase steps are applied in order to control the excitation of specific rotational Raman transitions. The outcome is the modification of the relative excitation between odd and even rotational states which allows the control of the symmetry and…
Universal charts for optical difference frequency generation in the terahertz domain
2010
We present a universal and rigorous approach to study difference frequency generation in the terahertz domain, keeping the number of degrees of freedom to a minimum, through the definition of a suitable figure of merit. The proposed method relies on suitably normalized charts, that enable to predict the optical-to-terahertz conversion efficiency of any system based on wave propagation in quadratic nonlinear materials. The predictions of our approach are found to be in good agreement with the best experimental results reported to date, enabling also to estimate the d22 nonlinear coefficient of high quality GaSe.
Integrated plasmonic waveguides: A mode solver based on density of states formulation
2009
International audience; We express the density of states (DOS) near guided resonances of plasmonic waveguides by using multiple-scattering theory. In direct analogy with the case of localized electronic defect states in condensed matter, we demonstrate that optical DOS variations follow a lorentzian profile near guided modes resonances. The lorentzian shape gives quantitative information on the guided modes (effective index, propagation length, and polarization state). We numerically investigate both leaky and bound (lossy) modes supported by dielectric-loaded surface-plasmon-polariton waveguides.
In vitro optical performance of a new aberration-free intraocular lens
2014
To assess the optical performance of the new EnVista intraocular lens (IOL). Four aspheric IOLs were evaluated; the new EnVista is one amoung them. This IOL, similarly to the Z-Flex HB and the Bi-Flex 1.8 667AB ones, has a neutral aspheric design, whereas the fourth IOL under test (AcrySof IQ IOL SN60WF) presents a negative spherical aberration (SA). The IOL’s aberration patterns were measured in vitro, by setting them up on an optical bench. From these aberration-pattern data, the modulation transfer function (MTF), the average modulation values, and the points spread function (PSF) were calculated. Furthermore, in order to assess the potential optical quality that these IOLs would yield o…
Spatio-temporal Characteristics of THz Emission at the Subwavelength Scale via Optical Rectification
2011
Highly localized THz emission via optical rectification in thin nonlinear crystals is a promising method for subwavelength microscopy. We present here the peculiar THz spatio-temporal characteristics induced by the non-paraxial generation regime.
<title>Photoinduced AsSeS thin film phase plates as adaptive optics mirrors for eye aberration correction</title>
2008
Amorphous chalcogenide thin films are excellent materials for holographic recordings. AsSeS thin film coating is a useful optical material for it's thickness to be easily corrected with the use of exposure to light and consecutive chemical etching. Following properties allow to treat the surface of AsSeS chalcogenide films and to use them in adaptive optics systems for correction of the optical wavefront. Hereby, we characterize AsSeS film properties to be used for correction of optical aberrations of the human eye. The thickness of the film is characterized with the method of spectrodensitometry and the surface profile depth with a Hartman- Shack waveform analyzator.
In vitro optical performance of nonrotational symmetric and refractive-diffractive aspheric multifocal intraocular lenses: impact of tilt and decentr…
2012
Purpose To evaluate the optical quality of Acrysof Restor SN6AD1 refractive–diffractive +3.00 D and Lentis Mplus LS-312 nonrotational symmetric +3.00 D aspheric multifocal intraocular lenses (IOLs) and analyze the effect of tilt and decentration. Setting University of Valencia, Valencia, and University of Murcia, Murcia, Spain. Design Experimental study. Methods An artificial model eye was used to measure wavefront aberrations of both IOL models. The modulation transfer function (MTF) and point-spread function (PSF) were calculated for a 5.0 mm pupil and under 5 situations: centered, 0.2 mm and 0.4 mm decentered, and 2 degrees and 4 degrees tilted. Results The refractive–diffractive IOL had…
Spatial light modulator phase mask implementation of wavefront encoded 3D computational-optical microscopy
2015
Spatial light modulator (SLM) implementation of wavefront encoding enables various types of engineered pointspread functions (PSFs), including the generalized-cubic and squared-cubic phase mask wavefront encoded (WFE) PSFs, shown to reduce the impact of sample-induced spherical aberration in fluorescence microscopy. This investigation validates dynamic experimental parameter variation of these WFE-PSFs. We find that particular design parameter bounds exist, within which the divergence of computed and experimental WFE-PSFs is of the same order of magnitude as that of computed and experimental conventional PSFs, such that model-based approaches for solving the inverse imaging problem can be a…
Experimental validation of a customized phase mask designed to enable efficient computational optical sectioning microscopy through wavefront encodin…
2017
In this paper, wavefront-encoded (WFE) computational optical sectioning microscopy (COSM) using a fabricated square cubic (SQUBIC) phase mask, designed to render the system less sensitive to depth-induced aberration, is investigated. The WFE-COSM system is characterized by a point spread function (PSF) that does not vary as rapidly with imaging depth compared to the conventional system. Thus, in WFE-COSM, image restoration from large volumes can be achieved using computationally efficient space-invariant (SI) algorithms, thereby avoiding the use of depth-variant algorithms. The fabricated SQUBIC phase mask was first evaluated and found to have a 75% fidelity compared to the theoretical desi…
Development of Slewing Mirror Telescope Optical System for the UFFO-pathfinder
2013
The Slewing Mirror Telescope (SMT) is the UV/optical telescope of UFFO-pathfinder. The SMT optical system is a Ritchey-Chretien (RC) telescope of 100 mm diameter pointed by means of a gimbal-mounted flat mirror in front of the telescope. The RC telescope has a 17 × 17arcmin2 in Field of View and 4.3 arcsec resolution (full width half maximum of the point spread function) The beam-steering mirror enables the SMT to access a 35 × 35degree region and point and settle within 1 sec. All mirrors were fabricated to about 0.02 wavelengths RMS in wave front error (WFE) and 84.7% average reflectivity over 200 nm ~ 650 nm. The RC telescope was aligned to 0.05 wavelengths RMS in WFE (test wavelength 63…