Noise in optical amplifiers

This article presents an application of a recently published probablistic model for traveling wave optical amplification. Both optical signal and amplified spontaneous emission (ASE) noise are modeled as bunches of photons traveling along the amplifying region with size varying according to simple random rules. The results of the theory enable one to obtain a complete and accurate characterization of the signal and noise counting at the amplifier output. On the basis of the above statistics, we find a realistic evaluation of the limits imposed by both quantum and ASE noise on the performances of a receiver including an optical amplifier at a preamplifier stage.     

High brightness operation of a XeCl laser with negative branch unstable resonators

Confocal and non-confocal negative branch unstable resonators with an intracavity spatial filter have been applied to a high-gain short-pulse UV preionized XeCl laser. The near- and far-field radiation characteristics have been investigated in both configurations. Laser beams of larger brightness have been obtained with non-confocal schemes. A maximum beam brightness of 1.3×10¹⁴ Wcm^–2Sr^–1 has been achieved.     

Photoelectron spectra of nitrones and nitrile oxides

The photoelectron spectra of five nitrones—N-t-butyl-, C-phenyl-N-methyl-, C-phenyl-N-t-butyl-, C-mesityl-N-methyl-nitrone and dihydroisoquin     

Nonlinear semigroup approach to a class of evolution equations arising from percolation in sandbanks

Summary In the framework of the theory of nonlinear contraction semigroups we study a class of parabolic variational inequalities arising from a model of percolation in gently sloping beaches. Some existence and uniqueness results are proven and the asymptotic behavior of the solutions is investigated.This work was done while the first author was visiting the «Laboratoire d'Analyse Numérique, Université P. et M. Curie, Paris», in 1985–86.     

Electron-beam-induced emission of KrXe+

The emission of KrXe⁺ was studied in Kr-Xe mixtures excited by an intense beam of fast electrons using time-resolved spectroscopy techniques. Previous works are discussed and the discrepancies are explained by noting that the emission band around 490 nm is affected by atomic transitions. Time constants and rate constants for the formation of the molecular ion are given.     

Kinetic studies of Kr2 Cl in electron-beam excited gas mixtures

Gas mixtures containing atomic krypton and carbon-tetrachloride were excited using intense electron beam pulses. The fluorescence produced by Kr₂Cl¹ was studied using time-resolved spectroscopic techniques. The lifetime (470 ns) and the quenching rate constants of Kr₂Cl¹ were deduced from the measurements.