A laser is a light source that generates an intense beam of coherent monochromatic light (or other electromagnetic radiation) by stimulated emission of photons from excited atoms or molecules. The word laser stands for Light Amplification by Stimulated Emission of Radiation.
Some terms related with laser:
Stimulated absorption: The electron in its ground state absorbs some energy (E1) and jumps to higher energy state (E2). This process is called stimulated absorption.
Spontaneous emission: The electron cannot remain in its excited state for long time. Its life time is about 10-8 sec. It spontaneously return back to its ground state by emitting a photon equal to the energy different of two states. This is called spontaneous emission.
Simulated emission: If an electron in its excited stated is forced to return back to its ground state is called stimulated emission.
Metastable state: The life of an electron in it excited state is about 10-8 sec. But if the electron stays in the excited state for a longer time about 10-3 sec then it is called metastable state.
Population inversion: Generally, the number of electrons is greater in ground state and only a few are available on excited state due to thermal energy. But if somehow we make the number of electrons in the excited state more than that of in ground state, such condition is called population inversion.
Optical pumping: The method of achieving population inversion by supplying energy to ground state electrons by the incidence of photons is called optical pumping.
Electric pumping: The method of achieving population inversion by applying potential difference is called electric pumping.
Properties of laser:
- The laser light is nearly monochromatic
- They do not show the tendency to diverge at all.
- The beam is very intense.
- The light is coherent and in phase with each other.
Uses of laser:
- Lasers are used in radio communication in outer space.
- It is used to weld metals.
- It is used in scientific researches.
- It is used in holography.
- It is used in piercing holes in metals.
- It s used to detect objects at great distances.