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What is Ruby Laser?

by Harpreet_Physics


In 1960, Maiman constructed the Ruby laser. It is a three-level solid-state laser. However, very few solid-state lasers produce visible light. But Ruby laser is one of them and is emitting red light of wavelength 694.3 nm  in lasing action.

Construction of Ruby Laser

A ruby laser made up of three important elements named as laser medium, the pump source and the optical resonator.

Laser Medium

Ruby (Al2O3+Cr2O3) is a crystal of Aluminium oxide, in which 0.05% of Al+3 ions are replaced by the Cr+3 ions. Also the colour of the rod is pink. However, The active medium in the ruby rod is Cr+3 ions. In ruby lasers, the rod is generally 4cm long and has a diameter of 5mm. The ruby has good thermal properties.

Ruby Laser
Figure : Ruby Laser

The pump source

A helical xenon flash tube surrounds the ruby rod. Also, It provides the pumping light to excite the chromium ions into upper energy levels. 

We know that population inversion is an essential requirement to achieve laser emission. Population inversion is the process of achieving a greater population of a higher energy state than the lower energy state. To achieve population inversion, we need to supply energy to the laser medium i.e. to ruby crystal.

Xenon flash tube emit thousands of joules of energy in a few milliseconds. But the chromium ions utilized only a  part of that energy. While the rest energy heats the apparatus. Cooling arrangement is playing an important role in the experimental set up. It keeps the system at normal temperatures.

Optical Resonator

Both the ends of the rods are highly polished and made strictly parallel. The ends are silvered. One end becomes partially reflected the laser beam was emitted through that end and the other end fully reflected to reflect all the rays of light striking it.

Drawbacks of the Ruby laser

  • Firstly, The laser requires high pumping power.
  • Secondly, The efficiency is very small.
  • Also, It is a pulse laser

 Application of the Ruby laser

  • Ruby lasers are in optical photography
  • For the measurement of plasma properties such as electron density and temperature, this can help.
  • In addition, it is used to remove the melanin from the skin.
  • It can be used for the recording of holograms.

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