DIFFRACTIVE EFFECTS AND NOISE IN SHORT PULSE FREE-ELECTRON LASERS (LETHARGY, QUANTUM OPTICS, COMERENCE, NONLINEAR).

摘要

Almost all previous work on free-electron laser theory for systems in which the slippage distance of the optical pulse is comparable to the length of the electron micropulse has been done without noise using a one-dimensional model. Three-dimensional effects were included by means of a filling factor. In this thesis, I extend the usual model to include both electron shot noise and quantum fluctuations. Several radial modes are then added to the simulation in order to include two-dimensional effects.;The extension of the simulation of two dimensions causes no large changes in the behavior as long as the higher order radial modes are strongly attenuated. When the losses for the higher order modes are reduced, the range of cavity lengths over which the laser operates is reduced and the peak gain is increased. In addition, the small signal frequency is downshifted from the value for a single mode. A heuristic explanation for this phenomenon is advanced.;The results of the simulation are compared with experimental results obtained from the Stanford laser. The cavity length detuning curve is shorter and the gain is lower than expected. No evidence is seen for the sideband instability which is anticipated from the simulations.;It is found that noise effects are dominated by electron shot noise, which is essentially a classical phenomenon. The laser startup with noise is seen to be more realistic than with artificial seed pulses. In addition, the laser startup near the point of synchronous cavity length is much faster than with no noise and the laser operates weakly for cavity lengths longer than the synchronous length.