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• What are the Characteristics of LASER light? What are the properties of LASER Light?

• How many types of LASER?

The LASER has following characteristics:
i) Monochromatic:

We know that the wavelength (or the frequency) of light decides its color. The ordinary light contains several electromagnetic waves of different colors (or different wavelengths). Generally, in a laser the light is produced by a specific atomic transition. Hence, the laser light is nearly monochromatic, means it has only one specific color or wavelength rather than so many wavelengths.

ii) Coherent:

In a laser, the process of stimulated emission produces photons of electromagnetic radiation. Thus, it is highly coherent, i.e. all the waves of a laser beam are in phase with one another.

iii) Collimated:

Due to the use of optical resonator, all the electromagnetic waves emitted by a laser travel in the same direction, exactly parallel to one another. This means that laser beams are very narrow and does not spread out much.

iv) Highly intense:

Since the laser produces a collimated beam of coherent electromagnetic waves, travelling in the same direction. Thus, they interfere constructively with each other and hence the intensity (power per unit area) of a laser beam is much greater than the intensity of any other source of electromagnetic radiation.

Types of Lasers

Generally, the lasers are categorized based on the type of active medium used. The active medium may be a solid, gas, liquid or semiconductor:

Solid-state lasers:

Generally, a rod of suitable material is used as active medium in a solid- state laser (e.g. ruby laser and Nd:YAG laser).

Gas lasers:

The active medium of a gas laser is in the gaseous form (e.g. He-Ne laser and CO2 laser).

Dye lasers:

They use liquid solution or suspension of an organic dye (e.g. rhodamine or fluorescein) as active media. They are tunable and capable to produce a wider range of wavelengths.

Semiconductor lasers:

In these lasers, the laser action is performed in a p-n junction diode. They are very compact in size and required very low power.

Lasers may also be categorised based on light produced by them as pulsed laser and continuous wave laser. As the names suggested, the pulsed laser emits light in the form of very short pulses (typically of the order of a few hundred microseconds to a few milliseconds) while the continuous wave laser emits light in the continuous wave form.