Answer to Question #202109 in Optics for prachi

Question

Why pumping is necessary for laser action? Compare and contrast three level and four level pumping schemes for lasers.

Answer 1

Laser pumping is the act of vitality exchange from an outside source into the pick-up medium of a laser. ... In this condition, the instrument of invigorated outflow can take put and the medium can act as a laser or an optical enhancer. The pump control must be higher than the lasing edge of the laser.

In a three-level framework, the laser move closes on the ground state. The unpumped pick-up medium shows solid retention on the laser move. ... Center: a four-level framework, where the laser move closes on a level over the ground state, which is rapidly eliminated e.g. by means of phonons.