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Laser technology is one of the most rapidly developing areas in modern technology. Laser was born out of curiosity, but now the world is curious about it. Laser emits  light by the stimulation of photons. In lasers atoms of crystals such as ruby are excited in a laser cavity to have a higher number of high energy levels. Lasers can be pinpointed to very tiny spots thus achieving a high radiance. 

Green laser pointers have a  wavelength of 532 nm , and are about 50 times stronger than red laser pointers.


Laser Invention.


Theodore Harold Maiman an American physicist generated the world's laser beam from a ruby rod in 1960. In 1917 Albert Einstein established the theoretic foundations for laser. The working principles of lasers were outlined by American physicists Charles Hard Townes and Arthur Leonard Schawlow in 1958. But a practical working laser was made out of a ruby rod on May 16,1960.


I wonder how does a laser work?


A laser is defined as a device that emits light through a process called stimulated emission. The   LASER is an acronym of "Light Amplification by Stimulated Emission".

Laser is  just amplified light generated by stimulated emission. Lasers are possible because of the way light interacts with electrons. Laser generation involves three stages 

  • Absorption
  • Population inversion
  • Stimulated emission

In an atom electrons exist at specific energy levels of that atom or molecule. The energy level can be imagined as rings or orbits around a nucleus. The electrons jump from lower energy levels (inner orbits) to higher energy level(outer orbits) when energy is supplied this process is called Absorption. The electrons come back to their original respective energy levels by releasing energy in the form of photons. This is called spontaneous emission. The substance which emits light when excited is called gain medium or laser medium. When a sizable population of electrons resides in higher level this is called population inversion. This is achieved by a process called energy pumping. 


Population inversion sets the stage for stimulated emission of multiple photons. This is the precondition for light amplification which occurs in laser. A set of mirrors mirrors called optical cavity are used so that the light bounces back, it increases in strength, resulting amplification of energy.


Characteristics of a laser:

  •  The light is coherent with all the waves exactly in phase with each other.
  •  Laser beam hardly diverges. i.e., The laser rays are almost parallel.
  •  The beam is nearly monochromatic.
  •  The laser beam is extremely intense. The beam can produce a temperature of 104oC at a focused point.

Types of Lasers.

Types of Lasers can be divided into gas lasers, solid state lasers and liquid lasers according to the active medium used.

Gas lasers.


Gas Lasers can be further divided into neutral atom, ion and molecular lasers, whose lasing mediums are neutral atoms, ions or gas molecules respectively. Helium-neon (He-Ne) laser is a kind of neutral atom gas laser,it is widely used in holography, scanning, measurement, optical fiber communication, etc. It is the most popular visible light laser. Carbon dioxide laser is a typical molecular gas laser. CO2 laser is widely used in laser machining, welding and surface treating.


Solid State Lasers.


In solid state lasers, ions are suspended in crystalline matrix to generate laser light. The ions emit electrons when excited, the crystalline matrix spread the energy among the ions. The first solid state laser is ruby laser but it is no longer used because of its low efficiency. Two common solid state lasers are Nd:YAG lasers and Nd:glass lasers.Both use krypton or xenon flash lamps for optical pumping. Nd:YAG lasers is used in material processing, range finding, laser target designation, surgery, research, pumping other lasers.Nd:glass lasers are suitable for hole piercing and deep keyhole welding operations.


Liquid Lasers.


Liquid Lasers use large organic dye molecules as the active lasing medium. These lasers can lase in a wide frequency range, i.e. they are frequency tunable. The spectral range of dyes covers infrared, visible and ultraviolet light.Pumping is done by another pulsed/continuous laser, or by pulsed lamp. These lasers are used in spectroscopic analysis and photochemical experiments.


Applications of Lasers.


Lasers have made way into all aspects of our modern life. 

  • They are used in spectroscopy, lunar ranging, material processing, photo chemistry.
  • In military, lasers are used for targeting firearms.
  • In dentistry, they are used for regular teeth cleaning and oral surgeries.
  • Vision corrections.
  • Removal of tumors.
  • Commercially used for cutting, welding, engraving, printing and storage, scanning, holography.
  • Lasers are also used in playing laser games.