Introduction to LASER
The word LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. The microwave predecessor of the laser, the MASER, was developed first. In the early technical literature, the laser was called an optical maser. MASER is an acronym for Microwave Amplification by Stimulated Emission of Radiation. This device produces coherent electromagnetic waves through amplification by stimulated emission. The first maser was built by Charles H. Townes, James P. Gordon, and Herbert J. Zeiger at Columbia University in 1953. Charles H. Townes, Nikolay Basov, and Alexander Prokhorov were awarded the 1964 Nobel Prize in Physics for theoretical work leading to the maser.
The important feature of Laser from other light sources is their coherence. Laser beams can be focused to very small spots, achieving a very high irradiance, they have low divergence in order to concentrate their power at a great distance. Lasers are used in optical disk drives, laser printers, barcode scanners, photolithography for fiber-optic, semiconducting chip manufacturing, laser surgery, skin treatments, cutting, and welding materials, and military applications.
The light from the laser has some unique features;
Laser light is highly coherent
The wavelengths of the laser light are in phase in space and time. The emission of all photons is in phase.
Laser light is highly monochromatic
Ordinary white light is a combination of many different wavelengths. The light emitted from a laser is of one wavelength. All photons in the laser light have the same energy, same frequency, and the same wavelength.
Laser light is highly directional
Ordinary light from the sun or a light bulb is emitted in many directions away from the source. Laser light is emitted as a narrow beam in a specific direction.
Laser light is highly intense
All the photons in the laser beam are coherent, so the intensity of the laser beam is high.