For laser action to occur the medium used must have at least three energy levels what must be the nature of each of these levels? Why is three the minimum number?
Answers
Answer:
Medium plays a very important role for production of Laser . It can be Crystal, Solid,Liquid , Semiconductor or gas can be send to excited state. The material must have controlled purity ,size and shape and must have three energy levels.
Answer:
The condition for achieving laser action are
(I) There must be an inverted population i.e. more atoms in the excited state than in the ground state.
(ii) the excited state of the system should be in metastable state
(iii) The emitted photons must stimulate further emission
Medium plays a very important role for production of Laser .It can be Crystal, Solid, Liquid , Semiconductor or gas can be send to excited state.
The material must have controlled purity ,size and shape and must have three energy levels.
The medium should have three or four Energy Levels
1. Ground Energy Level
2. Met stable energy level
3. Excited energy level.
The material is pumped to level 3-- Excited state from Ground state --- Level 1 which comes down rapidly through Level 2 Through Spontaneous emission and again to level 1 by Stimulated emission from level 2 to level 1.
Where as For Four level Laser, The material is pumped to level 4 Excited level which will come down fast to level 3-- Met stable and from level 3 to level 2 through Stimulated emission
The material must have controlled purity ,size and shape and must have three energy levels.
Explanation: