TABLE OF CONTENTS LASER is the acronym for Light Amplification by Stimulated Emission of Radiation. The laser is the outgrowth of MASER which is a device that amplifies microwaves. The theory behind the maser operation was developed by the American physicist C. H. Townes and independently by the Russian physicists N. Basov and P. M. Prokhorov. The first successful maser, an ammonia maser, was built by Gordon, Zeiger, and Townes in 1954. Townes, Basov, and Prokhorov were awarded the Noble Prize in Physics in 1964 for their invention of the maser. Masers are cumbersome devices and they are now relegated to the back stage. The first successful laser was the ruby laser, a solid state laser built by the American physicist T. H. Maiman in 1960. The Helium-Neon laser, which is a gas laser, was developed by Ali Javan and his associates in 1961. Developments in semiconductor technology led to the fabrication of the solid state diode laser in 1962 by Hall and his co-workers, and at about the same time by Nathan and his associates. Solid state diode lasers are small in size, do not need any auxiliary equipment, and are nearly 60% efficient. Lasers find applications in many fields. They have brought amazing changes in many areas and caused spectacular developments in the field of communications. Lasers made optical communications possible.
The understanding of the working principle of a laser (or maser) requires an appreciation of quantum processes that take place...
