A Short Introduction to Laser Physics

P. Welch

Stig Stenholm

Surendra Singh

The chapter begins with a chronological summary of principal developments in the field of laser physics and a brief introduction to laser. The fundamental principles and processes involved in the operation of a laser are then introduced in a simple way by using Einstein theory of light-matter interaction. The properties of laser light that make it special are briefly discussed and many concepts which will be used and discussed in the rest of the book are introduced. A short introduction to the logical organization of the book is included to help the reader appreciate how the book will help in gaining an understanding of the physics of lasers.

Pierre Meystre, Murray Sargent

Takashi Nakajima

We present a scheme to control the spin-polarization of photoelectrons/photoions using short laser pulses. It is based on the pump-probe method. By exciting fine structure manifolds of a system by the short pump pulse with a sufficient bandwidth, a superposition of fine structure states is created. After the pump pulse, the coherently superposed excited state evolves in time under the field-free condition with a period determined by the inverse of energy difference between them. In terms of the spin state, this suggests that the different spin state evolves differently in time, leading to the time-varying spin-polarization. Therefore, varying the time delay between the pump and probe pulses leads to the control of spin states upon photoionization. Specific theoretical results are presented for two-valence-electron atoms, in particular for Mg, which demonstrate that, under certain conditions, not only the degree of spin-polarization but also its polarity can be manipulated through time delay. Furthermore, we propose a new technique to accelerate the coupling time by the introduction of a dressing laser with a few ns duration. Since the underline physics is rather general and transparent, the presented scheme may be potentially applied to nanostructures such as quantum wells and quantum dots.