Types of Lasers
A laser is composed of an active laser medium, or gain medium, and a resonant optical cavity. The Laser gain medium transfers external energy into the laser beam. It is a material with controlled purity, size, concentration, and shape, which amplifies the beam by the process of stimulated emission. The laser gain medium, in general, is pumped, by an external energy source including a flash lamp, another laser source, electric gas discharge, exothermic chemical reactions etc. . The pump energy is absorbed by the laser medium, exciting some of its particles into high-energy state where these can interact with light both by absorbing photons or by emitting photons. Under certain conditions, as mentioned in earlier sections, the amount of stimulated emission due to light that passes exceeds the amount of absorption resulting in amplification. Thus the basic components of a laser are:
- Lasing material e.g. crystal, glass, gas, semiconductor, dye, etc.
- Pump source that adds energy to the lasing material, e.g. flash lamp, electrical current to cause electron collisions, radiation from a laser, chemical reactions etc.
- Optical cavity, which consists of reflectors, acts as the feedback mechanism for light amplification.
Solid State lasers
Gas lasers
Free Electron lasers