Search results for "electromagnetic [radiation]"
showing 10 items of 873 documents
Emergence of X-Shaped Spatiotemporal Coherence in Optical Waves
2006
Considering the problem of parametric nonlinear interaction, we report the experimental observation of electromagnetic waves characterized by an X-shaped spatiotemporal coherence; i.e., coherence is neither spatial nor temporal, but skewed along specific spatiotemporal trajectories. The application of the usual, purely spatial or temporal, measures of coherence would erroneously lead to the conclusion that the field is fully incoherent. Such hidden coherence has been identified owing to an innovative diagnostic technique based on simultaneous analysis of both the spatial and temporal spectra.
Compact all-diffractive setup for spectral synthesis with non-uniform illumination
2009
Optical filters based on diffractive optical elements (DOE) have received increased attention since the development of the first synthetic spectrum as a tool for correlation spectroscopy [1]. The production of a synthetic spectrum requires the design of a DOE that transforms the spectrum associated with the incident light into the spectrum of interest. Based on this procedure, several approaches have been reported in the literature [1–4]. In general, these configurations employ angular dispersion elements for spectrum tailoring, so they are restricted to working off-axis, and most of them need an extra focusing refractive lens.
Electromagnetic energy within dielectric spheres
1987
We present exact and approximate analytic expressions for the time-averaged electromagnetic energy within dielectric spheres on the basis of rigorous Mie theory. Such information is of importance for the study of photochemical reactions within atmospheric water spheres. Numerical results show that on the average the energy inside a cloud droplet is enlarged by a factor exceeding 2 compared with that of a sphere of the same radius of the surrounding medium. In regions of resonance peaks the electromagnetic energy may be increased by more than 2 orders of magnitude.
A Novel Method Of Measuring Light Absorption On A Self-Assembled Single Quantum Dot
2005
Abstract. We present a novel method by wich excitonic interband optical transitions within single InAs self-assembled quantum dots can be directly observed in a transmission experiment. Due to the extremely high resolution of the tecnique, individual peaks associated to single exciton absorption resonances in single quantum dots can be spectrally resolved. Using this technique we investigate the oscillator strength, homogeneous linewidth and fine structure splitting in a collection of such individual resonances.
The role of nonlinear optical absorption in narrowband difference-frequency terahertz-wave generation
2010
We present a general analysis of the influence of nonlinear optical absorption on terahertz generation via optical difference frequency generation, when reaching for the quantum conversion efficiency limit. By casting the equations governing the process in a suitably normalized form, including either two-photon- or three-photon-absorption terms, we have been able to plot universal charts for phase matched optical-to-terahertz conversion for different values of the nonlinear absorption coefficients. We apply our analysis to some experiments reported to date, in order to understand to what extent multiphoton absorption could have played a role and also to predict the maximum achievable conver…
Unusual optical properties of the dense nonequilibrium plasmas
2005
A concise overview of new optical properties of dense nonequilibrium plasma formed on the solid state target boundary is given. In this chapter, we describe phenomena such as the third harmonic generation in the skin layer, collisionless electron heating in the high frequency skin-effect regime, absorption, and reflection and transmission of radiation by a plasma with anisotropic electron distribution.
The role of synchrotron self-absorption in the late radio emission of SN1993J
2001
The standard model for radio supernovae considers that the observed synchrotron radio emission arises from the high-energy shell that results from the strong interaction between the expanding supernova ejecta and the circumstellar medium. This emission is considered to be only partially absorbed by ionized thermal electrons in the circumstellar wind of the progenitor star. Based on a study of the radio light curves of the type II supernova SN1993J, we present evidence of synchrotron self-absorption. Our modeling of the radio light curves requires a large initial magnetic field, of about 30 Gauss, and the existence of an (initially) highly-relativistic population of electrons. We also show t…
Control of the high harmonic generation spectra by changing the molecule-laser field relative orientation
2010
The time dependent Schrodinger equation of a homonuclear diatomic molecule in the presence of a linearly polarized laser field is numerically solved by means of a split-operator parallel code. The calculations are carried out by assuming a single active electron model with fixed nuclei; a simplified two-dimensional model of the system is used. The highly nonlinear response of the electron wave function to the laser electric field stimulates the molecule to emit electromagnetic radiation consisting of a wide plateau of odd harmonics of the laser field. It is shown that the emitted spectrum can be finely controlled by changing the angle between the laser electric field and the molecular axis;…
Pulse-duration dependence of the isotopic effect in simple molecular ions driven by strong laser fields
2011
In this paper we discuss isotopic effects in simple molecular ions subjected to strong laser fields. We show that the intensity of the emitted spectra strongly depends upon both the nuclear mass of the molecular ions and the laser pulse duration. In particular, for short pulse duration [up to 8 optical cycles (o.c.)], we confirm the trend described in the most studied case in which the high-order harmonic generation is more efficient for heavier isotopes; in contrast, an interesting physical phenomenon is predicted for pulses longer than 16 o.c. characterized by an inverse effect in which lighter molecular species are responsible for higher-order harmonic emission.
Evidence of chiral bands in even-even nuclei
2018
Evidence for chiral doublet bands has been observed for the first time in the even-even nucleus 136 Nd . One chiral band was firmly established. Four other candidates for chiral bands were also identified, which can contribute to the realization of the multiple pairs of chiral doublet bands ( M χ D ) phenomenon. The observed bands are investigated by the constrained and tilted axis cranking covariant density functional theory (TAC-CDFT). Possible configurations have been explored. The experimental energy spectra, angular momenta, and B ( M 1 ) / B ( E 2 ) values for the assigned configurations are globally reproduced by TAC-CDFT. Calculated results support the chiral interpretation of the o…