Introduction to Optics
Including the tools and methods currently used by researchers and engineers, this book covers the essential concepts of comprehension and reports the great progress of the current knowledge in optics.
TABLE OF CONTENTS Introduction to Optics
Chapter 9: Lasers
9.1 Laser, a Feedback Oscillator
9.1.1 Light Amplification by Stimulated Emission of Radiation
A laser is a device which, receiving energy from a pumping source, transfers this energy to a coherent light beam.
In the above definition the word light should not be taken literally, as the wavelength of lasers very often falls outside the famous octave (0.8 0.4 ?m) inside of which the human eye can see. Lasers can emit within the deep infrared (300 ?m) as well as within the visible or the ultraviolet (0.1. ?m). There is no theoretical limitation for obtaining stimulated emission with X-rays or even ?-rays. The family of presently existing lasers is extremely diversified and affects various branches of Physics and Chemistry. The lasers that are most often encountered are certainly semiconductor lasers, they easily emit in the near infrared (0.8-1.6 ?m) and their efficiency is exceptionally high (70%). Being produced in large quantities they are very cheap, all the more as their technology is very similar to microelectronics.
Lasers, a Brilliant Result of Basic Research
It was at the end of the 1950s that the American physicist Thomas H. Maiman obtained a burst of coherent light from of a ruby rod that had been placed along the axis of a helical flash tube, initially designed for professional film production. For many scientific or technical inventions, such as steam engines or superconductivity or even most electromagnetic effects, experimentalists or engineers had discovered and developed the phenomena before the approach...
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