laser coherence

When a laser beam is emitted from a source, there may be phase difference between the beams at different points that is it may be possible that there may be some time gap between the two atoms to come from upper energy level to lower energy level. The term coherence refers to the degree of co-relation between the phases.

In other words, two or more light waves are said to be coherent if they bear a constant phase relation among themselves.

Reference: This article is referred from my authored book “optics and lasers” having ISBN 81-272-2948-2. In case of any doubt, post in the comment section.

Properties of laser

A laser beam has following important characteristics:

  • Divergence or directionality:  laser is highly directional beam.
  • monochromaticity: laser is monochromatic that is it has single wavelength
  • brightness
  • coherence

Reference: This article is referred from my authored book “optics and lasers” having ISBN 81-272-2948-2. In case of any doubt, post in the comment section.

types of lasers

The lasers can be classified by various ways, as explained below:

a) State of laser medium: According to state of laser medium, we have solid state lasers like ruby laser, gas lasers like helium-neon laser.

b) Mechanism of pumping: According to pumping mechanism, we have flash light or optical pumping based lasers like ruby laser, electric discharge based laser like He-Ne laser.

c) Nature of output: According to nature of output, we have pulsed lasers like ruby laser and continuous wave lasers like he-Ne laser.

d) Wavelength of output: According to wavelength of lasers, we have ultra violet, visible and infrared lasers.

Reference: This article is referred from my authored book “optics and lasers” having ISBN 81-272-2948-2. In case of any doubt, post in the comment section.