Introduction

Although this development has been deeply impressed in the minds of all of the early researchers in this eld, it may well escape the knowledge of young researchers approaching this area for the rst time. Graduate students in physics and electronics can prot from such knowledge, and the level of exposition has been chosen accordingly. Whenever possible, original authors have been allowed to speak for themselves through their papers, and short biographies of the leaders in the eld have been included. In this second edition, the development of lasers has been retrieved up to the present, including nonlinear optics, ultrashort pulses, and some special issues.