Search results for "RAMAN"

Mellin transform approach for the solution of coupled systems of fractional differential equations

2015

In this paper, the solution of a multi-order, multi-degree-of-freedom fractional differential equation is addressed by using the Mellin integral transform. By taking advantage of a technique that relates the transformed function, in points of the complex plane differing in the value of their real part, the solution is found in the Mellin domain by solving a linear set of algebraic equations. The approximate solution of the differential (or integral) equation is restored, in the time domain, by using the inverse Mellin transform in its discretized form.

Le indagini scientifiche per lo studio e la conservazione dei beni culturali : un approccio analitico integrato, la conoscenza dei materiali costitut…

2019

The icon Virgin Hodegetria, now in Santa Maria Nuova Cathedral in Monreale near Palermo (Italy), probably dates from the beginning of thirteen century could be considered one of the earliest examples of medieval icon in Sicily. The icon is distinguished from other southern icons by the strong Byzantine matrix and by its size (169x131x3 cm). Since 2015, the icon is part of the Arab-Norman Palermo UNESCO Heritage. This paper will deal with historical and scientific investigations on the icon to better understand the painting materials, the executive technique and to resolve question about on-going restoration in planning a complex conservation project. Examination of the icon was both non-inv…

One Shot Laser Pulse Induced Reversible Spin Transition in the Spin-Crossover Complex [Fe(C4H4N2){Pt(CN)4}] at Room Temperature

2005

Molecule non-radiative coupling to a metallic nanosphere: an optical theorem treatment.

2009

The non-radiative coupling of a molecule to a metallic spherical particle is approximated by a sum involving particle quasistatic polarizabilities. We demonstrate that energy transfer from molecule to particle satisfies the optical theorem if size effects corrections are properly introduced into the quasistatic polarizabilities. We hope that this simplified model gives valuable information on the coupling mechanism between molecule and metallic nanos-tructures available for, e.g., surface enhanced spectroscopy signal analysis.

Control processes for stimulated Raman scattering in optical fibers by dual-frequency pumping

1998

We pointed out that with nondegenerate frequency, and orthogonally polarized pump waves, the SRS may be suppressed in one of the axes of a highly birefringent fiber either via a four wave mixing (FWM) parametric process, or through the orthogonal component of the Raman nonlinearity.

Interaction between optical parabolic pulses in a Raman fiber amplifier

2009

We investigate the interaction between optical parabolic pulses in a Raman fiber amplifier. Self-similar amplification of two identical time-delayed pulses creates an oscillation which further evolves into a train of dark solitons through the combined effects of non-linearity, normal dispersion and adiabatic Raman gain. Theoretical predictions are in good agreement with experimental results.

Emergence of extreme events in fiber-based parametric processes driven by a partially incoherent pump wave

2009

Modulation instability (MI) generated by a picosecond coherent pulse has been recently identified as the key element of the generation of optical rogue-waves in supercontinuum-based systems [1]. Similar rare but highly energetic pulse structures can also appear in non-solitonic configurations such as Raman amplifiers driven by a partially incoherent pump wave propagating in fibres with low group velocity dispersion [2]. Therefore, one may wonder whether optical rogue-like event can also occur in MI-based amplifier because both Raman and parametric amplifiers benefit from a quasi-instantaneous gain. We provide here experimental evidence of rare optical events in a parametric amplifier in pre…

Collisions between similaritons in optical fiber amplifiers

2009

We consider the self-similar amplification of two optical pulses of different wavelengths in order to investigate the effects of a collision between two similaritons. We theoretically demonstrate that similaritons are stable against collisions in a Raman amplifier: similaritons evolve separately in the amplifier without modification of the scaling of their temporal width and chirp and by conserving their velocities, only interact during their overlap and regain their parabolic form after collision. We show both theoretically and experimentally that the collision of two similaritons induces a sinusoidal modulation inside the overlap region, whose frequency decreases during the interaction. T…

Highly-chirped similaritons generation from a mode-locked fiber laser

2007

In this communication, we report experimental and numerical results on dynamics and propagation of self-similar pulses in a passively mode-locked ytterbium doped DC fiber laser.

Generation and characterization of 06-THz polarization domain-wall trains in an ultralow-birefringence spun fiber

2007

Polarization domain-wall (PDW) trains have been generated at a repetition rate of 0.6 THz in an ultralow-birefringence spun optical fiber and measured by use of an adapted frequency-resolved optical gating technique. Characterization of the intensity and the phase of the PDW train shows complete switching between adjacent domains of counterrotating circular polarizations and directly confirms predictions based on numerical simulations of the incoherently coupled nonlinear Schrödinger equations.