This book is on different nonlinear schemes of Free Electron Lasers, Laser Accelerators, and Electron-Positron pair production and covers the theory of interaction of strong and super strong laser fields with charged particles and vacuum. These topics will be in the center of fundamental research in the next decade. The author, who has over 30 years of experience in this field, has developed non-linear theory and new approaches to solve respective relativistic classical and quantum problems. The book will be especially useful for researchers, students and industry practitioners in the fields of Particle and Laser Physics.