This is largely a stand-alone chapter on the working of lasers and has been planned as a prelude to an in-depth understanding of laser fundamentals. Entitled “Lasers: At a Glance,” this chapter is intended to impart rudimentary knowledge to the readers to prepare them to fathom a laser more intelligibly as they read through the latter chapters of this part of the book dealing with the physics of laser more intricately. This chapter, in the beginning, familiarizes the readers on the working of a fluorescent light source and makes them ponder how this source, which emits light all around it, can be made to throw light in a particular direction. It then exposes the readers to the basic concepts of stimulated emission, population inversion, and cavity. The anecdote picked from the history enveloping the invention of lasers by Maiman provides a seamless ending to this stand-alone chapter.

1. 1.

   Interested readers may refer in this context to the bookThe Laser Odyssey by Theodore Maiman, creator of the world’s first laser.

2. 2.

   Cosmic radiation that reaches the Earth surface from the outer space is responsible for the presence of charged particles in our atmosphere.

3. 3.

   This can be achieved if somehow the population is selectively transferred from the source to the excited level.

4. 4.

   The increase in the number of photons is exponential and is proportional toe^gl where gaing is directly proportional to population inversion andl is the length of the active medium.

5. 5.

   The amplification in certain cases can be extremely high in a single pass itself. This is called amplified spontaneous emission.

6. 6.

   If the product of dimension of any two variables equals the dimension of the Planck’s constanth, then they are called canonically conjugate variables in the present context.

7. 7.

   Although this fact was not explicitly mentioned by Maiman in the paper he wrote reporting the invention of the laser, the non-emergence of a beam of light points to the cavity less operation of the very first laser. This aspect was also corroborated by Nobel Laureate Charles Townes in his article “The First laser” inA Century of Nature: Twenty-One Discoveries That Changed Science and the World Nature, 2003, Ed: Laura Garwin and Tim Lincoln.

8. 8.

   The text and illustrations here are not a reproduction from Maiman’s original research paper. To make it palatable to the readers, illustrations have been redrawn and accompanied by suitable explanation to elucidate the central theme of his work. Interested readers are referred to his original paper [T. H. Maiman, Nature 187: 493–494, August 6, 1960] to know about the invention of laser in the inventor’s own words.

Authors and Affiliations

1. Former Head, Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai, India

   Dhruba J. Biswas

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