A Short History of Laser H R Khalesifard

A Short History of Laser H. R. Khalesifard Institute for Advanced Studies in Basic Sciences Email: khalesi@iasbs. ac. ir

Stimulated emission, The MASER and The LASER n (1916) The concept of stimulated emission Albert Einstein

Absorption E 2 E 1 Spontaneous Emission E 2 Stimulated Emission E 1

n (1928) Observation of negative absorption or stimulated emission near to resonant wavelengths, Rudolf Walther Ladenburg E 2 E 1 Stimulated Emission (negative absorption)

Absorption n E 2, N 2 E 1, N 1 Stimulated Emission (1930 s) If a physical system be in thermodynamic equilibrium the population inversion and so the stimulated emission is impossible

Light (Microwave) Amplification by Stimulated Emission of Radiation LASER (MASER)

The Maser Left to right: Prokhorov, Townes and Basov at the Lebedev institute (1964 Nobel prize in Physics for developing the “Maser-Laser principle”)

Townes (left) and Gordon (right) and the ammonia maser they had built at Colombia University

The LASER n n n (1951) V. A. Fabrikant “A method for the amplification of electromagnetic radiation (ultraviolet, visible, infrared, and radio waves)” patented in Soviet Union. (1958) Townes and Arthur L. Schawlow, “Infrared and Optical Masers, ” Physical Review (1958) Gordon Gould definition of “Laser” as “Light Amplification by Stimulated Emission of Radiation” (1960) Schawlow and Townes U. S. Patent No. 2, 929, 922 (1960) Theodore Maiman Invention of the first Ruby Laser (1960) Ali Javan The first He-Ne Laser

Arthur Schawlow adjusting a ruby laser that he made at the Bell Labs in 1960

Maiman and the first ruby laser

Ali Javan and the first He-Ne Laser

The laser cavity length should be multiple of light wavelength

The laser Structure End Mirror Pump Front Mirror Lasing Medium

Properties of Laser Beam A laser beam n Is monochrome n Can be focused in a very small point n Is intense n Is Coherent n Has a very low divergence n Can be compressed in time up to few femto second

Applications of Laser n n (1960 s) “A solution looking for a problem” (Present time) Medicine, Research, Supermarkets, Entertainment, Industry, Military, Communication, Art, Information technology, …