[en] The role of the noncompact Su(1,1) group in optics is discussed. It is shown that it can be used to analyze a wide class of phenomena in both quantum and classical optics

[en] An experimental investigation of the influence of the initiating discharge characteristics on the performance of a large aperture, pulsed, HF chemical laser is presented. The laser was operated with SF⁶-H² and SF⁶-C⁴H¹⁰ gas mixtures. Accurate measurements of the voltage-current waveforms for two different initiation circuit configurations have permitted to gain some insight into the mechanisms connecting the discharge temporal evolution with the F atom concentration and production rate, and, therefore, with the pumping reaction rate. It is shown that with a fast deposition of electrical energy into the laser medium, the efficiency of converting this energy into laser energy can be quite high (4.5%), even for a large aperture device. (author)

No abstract available

[en] After briefly describing the basic properties of thermohydrodynamic gas lenses, we show that their appropriate use in a gas loaded free electron laser increases the small signal gain by a factor even higher than 2. (orig.)

[en] This paper reviews the main problems encountered in the design of an optical system for transmitting high fluence radiation in a laser driven accelerator. Particular attention is devoted to the analysis of mirror and waveguide systems. (orig.)

[en] The equation of motion for an electron in a free electron laser amplifier are written in hamiltonian form, and exactly solved for the circular polarized case. Successively, an approximate solution for a general polarization (elliptical or linear) and weak laser field is obtained by a relativistic generalization of the two timing technique. Finally, the theoretical perturbative results are confirmed by comparison with numerical solutions

[en] The driving current of a free electron laser is calculated by including terms, generally neglected, which represent the effect of the e-beam bending due to the electron wiggling. The 3D wave equation is solved by representing the field as a superposition of space harmonics. The transverse distribution of the field is accounted for by expanding it in a series of Gauss-Laguerre modes. A simple expression of the correction on the complex propagation constant caused by the electron wiggling is obtained. (orig.)

[en] The driving current for an FEL amplifier operating in the exponential growth regime is derived for a frequency close to the reasonance one and for a finite value of the wiggling radius of the electrons. The wave equation is solved by applying the generalized Rayleigh-Ritz variational principle. In particular, it is shown that the dispersion equation for the propagation constant can be put into the same form as that derived in absence of wiggling. (orig.)

[en] In the present paper a general model of plasma instabilities in high-power e-beam sustained CO₂ laser amplifiers is illustrated. This model improves the Nighan-Haas one by allowing explicitly for the various degrees of vibrational freedom and taking into account the stabilizing effect of the laser field intensity. Two numerical codes, which have been used to calculate the steady-state plasma properties needed to carry out the stability analysis, are also presented. The model has been used to test the degree of thermal and ionic instability of an EDCL device using four-component gas mixture (CO₂-N₂-He-CO)

[en] The radiation emitted by the linear undulator installed on a straight section of the ADONE storage ring is studied both experimentally and theoretically. In particular, expressions are provided for the field at finite distance, based on the complex Fresnel integral. In addition, several expressions are derived for the average intensity pattern as a function of the electron beam divergence and energy spread. These formulae are used for analysing the spectral and angular patterns of the radiation measured from a distance of 20 m from the undulator origin. The excellent quality of the undulator and the negligible influence on the pattern of the electron beam divergence are confirmed by the satisfactory agreement of the measured radiation field with the computer-generated one