Nonlinear Effects in High-Peak Power Nd: Glass Laser Systems

Abstract

We now begin an investigation of what may be regarded as the central problem in the design of high-peak power Nd:glass laser systems. The phenomena of self-focusing, discovered when high-power lasers first became available, presently limits the output of every laser system designed to operate at short (50–200 ps) pulse widths. Although the problem has yielded to a number of improvements in laser materials, most notably the development of low-nonlinearindex glasses (Chap.2), it is fair to say that the major developments leading to present-day laser systems that deliver multi-terawatt performance per beamline are due to the excellent work of colleagues at the Lawrence Livermore Laboratory. In particular, they deserve credit for such concepts as spatial filtering and imaging, to be treated in detail below; but, more importantly, the major advancement is in our understanding of the nonlinear effects, well known to the experimentalist in this area. Although the basics of self-focusing theory (Sect.7.2–4) were known for some time previous to the advent of the construction of large Nd:glass laser systems, the major contribution here is the development of semi-phenomenological theories that enable the laser designer to proceed with a great degree of confidence and reliably predict the operating characteristics of such a system. As is usually the case with systems of such complexity, it is impossible to simulate the exact physics in detail because it would call for a computational capability and expense that is beyond the resources of any single laboratory. Consequently, what we present in Sects.7.2–6 below is the current phenomenological understanding that has led to multi-terawatt performance of a number of laser systems in this country and abroad.