Search results for "Physics::Optics"
showing 10 items of 1958 documents
Phonon-induced optical superlattice
2005
We demonstrate the formation of a dynamic optical superlattice through the modulation of a semiconductor microcavity by stimulated acoustic phonons. The high coherent phonon population produces a folded optical dispersion relation with well-defined energy gaps and renormalized energy levels, which are accessed using reflection and diffraction experiments.
Diffraction-free propagation of subwavelength light beams in layered media
2010
Self-collimation of tightly localized laser beams demonstrated in periodic media relies on a perfect-matched rephasing of the Fourier constituents of the wavefield induced by a plane isofrequency curve. An alternate way paved for the achievement of such a phase matching condition developed a suitable spatial filtering in order to select those frequencies experiencing the same phase velocity projected over a given orientation. In principle this procedure is valid for complex structured metamaterials. However, a great majority of studies have focused on free-space propagation leading to the well-known Bessel beams. This paper is devoted to the analysis of this sort of nondiffracting beams tra…
Diffraction-managed superlensing using metallodielectric heterostructures
2012
We show that subwavelength diffracted wave fields may be managed inside multilayered plasmonic devices to achieve ultra-resolving lensing. For that purpose we first transform both homogeneous waves and a broad band of evanescent waves into propagating Bloch modes by means of a metal/dielectric (MD) superlattice. Beam spreading is subsequently compensated by means of negative refraction in a plasmon-induced anisotropic effective-medium that is cemented behind. A precise design of the superlens doublet may lead to nearly aberration-free images with subwavelength resolution in spite of using optical paths longer than a wavelength. This research was funded by the Spanish Ministry of Economy and…
Focal shift in optical waves with off-axis focus
2003
We present a formulation for a suitable description of the focal shift in optical waves that have an off-axis focus. This shift that is primarily produced along the chief axis is given in terms of the focal distance and depends only on a parameter that is named as the generalized Fresnel number. Any non-uniform, either truncated and non-apertured optical beam with off-axis focus may be considered.
Single-zone-plate achromatic fresnel-transform setup: Pattern tunability
1997
Abstract White-light point-source illumination results in the chromatic blurring of the optical field diffracted by an aperture. In this paper, broadband dispersion compensation for a continuous set of Fresnel diffraction patterns associated with an arbitrary input transparency is carried out, in a sequential way, by means of a single on-axis blazed zone plate. The input is illuminated with a white-light converging spherical wavefront and the diffractive lens is inserted at the virtual source plane. We recognize that the position of the input along the optical axis permits to achieve a different achromatic Fresnel diffraction pattern with low residual chromatic aberrations. The theory deriv…
Totally incoherent optical processing operations with achromatic diffraction-based setups
2000
We report on a novel family of totally incoherent, chromatic-dispersion compensated hybrid (refractive-diffractive) lens setups for implementing, in the Fraunhofer or in the Fresnel diffraction region, different achromatic diffraction-based processing operations.
Three-dimensional behavior of apodized nontelecentric focusing systems.
2002
The scalar field in the focal volume of nontelecentric apodized focusing systems cannot be accurately described by the Debye integral representation. By use of the Fresnel–Kirchhoff diffraction formula it is found that, if the aperture stop is axially displaced, the focal-volume structure is tuned. We analyze the influence of the apodizing function and find that, whereas axially superresolving pupil filters are highly sensitive to the focal-volume reshaping effect, axially apodizing filters are more inclined to the focal-shift effect.
Observation of optical Smith-Purcell radiation at an electron beam energy of 855 MeV.
2002
Smith-Purcell radiation, generated when a beam of charged particles passes close to the surface of a diffraction grating, has been studied in the visible spectral range at wavelengths of 360 and 546 nm with the low emittance 855 MeV electron beam of the Mainz Microtron MAMI. The beam focused to a spot size of $4 \ensuremath{\mu}\mathrm{m}$ (full width at half maximum) passed over optical diffraction gratings of echelle profiles with blaze angles of $0.8\ifmmode^\circ\else\textdegree\fi{}, 17.27\ifmmode^\circ\else\textdegree\fi{},$ and $41.12\ifmmode^\circ\else\textdegree\fi{}$ and grating periods of 0.833 and $9.09 \ensuremath{\mu}\mathrm{m}.$ Taking advantage of the specific emission chara…
Electromagnetic Singularities and Resonances in Near-Field Optical Probes
2007
Over the last two decades scanning near-field optical microscopy (SNOM) has demonstrated its ability to provide optical resolution significantly better than the diffraction limit (<20 nm). The general principle of SNOM relies on the approach of a nanometer-sized object in the optical near-field of a sample to be studied. This nano-object (NO) is usually the extremity of a probe. Regardless of the nature of the observed SNOM signal (inelastic scattering, fluorescence, etc.), the detection of the light is achieved in the far-field regime where the NO acts as a mediator between the optical near-field and the detector. Figure 1 is a schematic illustration of the SNOM principle.
Asymmetric transmission of transverse magnetic or radially polarized THZ waves through sub-wavelength gratings
2015
We have developed a metallic double circular grating with sub-wavelength slits which blocks radially polarized light incident from one of its sides and acts as a focusing diffractive element in the other direction. The proposed grating has been optimized for the sub-THz frequency range. Unidirectional transmission through the grating has been demonstrated experimentally at 0.1 THz. We have also developed a planar metallic double grating with sub-wavelength slits which blocks light with a transverse magnetic polarization incident from one of the grating sides and transmits radiation incident from the opposite direction into the +1 and −1 diffraction orders. These gratings which could be used…