Introduction

This introductory lesson is intended for people who need to understand the basic principles of how lasers work and their main properties. It will also present the different types of lasers available today. The lesson plan is as follows: The introduction (Part I) describes the history behind the invention of the laser and how it was already well-established in the collective culture even before its discovery. Part II explains the basic mechanisms involved in the interaction between the laser medium and the light source. Part III focuses on the role of the optical cavity (or resonator) and how it influences the properties of the laser beam. Part IV details the different operating modes. In fact, Parts III and IV show how a laser beam is defined by specific spatial, spectral and temporal values. Part V describes the different types of laser, according to their amplifying medium. Finally, Part VI lists some of the possible applications.