Nov 2016


November 18, 2016


Welcome back to our blog. The topic of discussion in this blog concerns LASER fundamentals. To get detailed and conceptual information on A-Level Physics, join JC Physics tuition which has been coaching students to clear many prestigious International Physics examinations and scholarship tests. Join one of the best Physics Tuition in Singapore and make way for a bright future.

LASER stands for Light Amplification by Stimulated Emission of Radiation. A LASER emits light coherently and is tightly packed in a small area which makes it different from other sources of light. The spatial coherence is the reason why the LASER is used for cutting, welding or lithography. The LASER beam can travel great distances without being dispersed and their ability to possess temporal coherence allows a ray of a very narrow spectrum to get emitted.

LASER is used in a variety of applications from laser printers to laser barcode scanners, from DNA Sequencing instruments to LASER surgery, from cutting to welding metals and from measuring speed to LASER light display for entertainment.

So now let’s look at how LASER is created. When an electron absorbs some energy from the photons which is incident onto it in the form of light or heat, its energy increases, and the electrons comes into the ‘excited’ state. When the electron absorbs enough energy to breach its own energy level and enter the excited energy level, it transitions to the higher energy levels and starts populating this energy level.

But the electron that has entered the higher energy level does not remain at the same level. It decays to a lower energy level which is vacant and in the process emits photons. This emission is spontaneous and is thus called spontaneous emission. The material with a huge number of atoms in the excited state results in radiation which is known as LASER emission or Lasing action.

The LASER emitted by the system has similar characteristics when compared to the incident light. It gives the LASER its coherence and helps in maintaining the monochromaticity and uniform polarization of the beam. Most LASERs follow the Gaussian beam which encounters minimum divergence while propagation.

There are different forms of LASERs being used currently. Some of them are discussed below:

  • Gas Lasers- HeNe Laser is the most primitive and basic laser developed. It is the simplest and most effective laser in practice. Other forms of gas lasers used are Carbon Dioxide lasers, Argon-ion laser, HeAg laser, NeCu laser, etc.
  • Chemical Lasers- Chemical lasers are generated as a result of the chemical reactions which allows a huge amount of energy to be emitted in a small amount of time. Some common examples of chemical lasers are Hydrogen fluoride laser, deuterium fluoride laser, etc.
  • Excimer Laser- Excimer laser uses a special type of gas laser which is powered by an electric discharge with excimer as the lasing medium. Photolithography and Lasik eye surgeries are done with the help of this machine.
  • Solid-state Laser- Doped glass rods are used in this laser for taking the electrons to the excited level. Ruby Laser is the most common form of solid-state laser.
  • Semiconductor Laser- Most semiconductor lasers are laser diodes, which are pumped with an electrical current in a region where an n-doped and a p-doped semiconductor material meet. Laser diodes are commonly used in Atomic Force Microscope to create a spot that moves as the cantilever defects.
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