Introduction

Abstract

Since the invention of the laser in the early 1960s, scientists and engineers have been producing and advancing ultra-short pulsed lasers to extraordinary capabilities. Starting from lasers operated in a continuous wave regime, ultra-short (picosecond to femtosecond) optical pulses are now commonplace in research laboratories and increasingly in the industrial and commercial sectors. For perspective, if 1s was scaled down to 1fs (0.000000000000001s), the age of the universe would scale to approximately 10min. Such ultra-short pulses allow us to gain unique insights into matter at the micrometer and nanometer scales, enabling the study of structures at the subatomic level. In the same way that a disco strobe light "freezes" the motion of dancers, an ultra-short pulse laser can "freeze" the motion of rapid events such as the dynamics of molecules. Therefore, it is now possible, for example, to measure the relaxation processes of carriers in semiconductors and the dynamics of chemical reaction, and even allows us to perform electrooptical sampling of high-speed electronics. The enormous impact of ultrafast optical sources has already been recognized in the attribution of two Nobel prizes to Zewail (1999) and Hansch (2005), for applications in femtochemistry and laser-based precision spectroscopy.