What is pumping in LASER? Give the types of pumping.
The process of raising large number of atoms from lower energy to a higher energy level is called pumping.
Types of pumping:
1. Optical pumping: which uses strong light source for excitation.
2. Electrical pumping: which uses electron impact for excitation.
3. Chemical pumping: which uses chemical reactions for excitation.
4. Direct pumping: which uses direct conversion of electric energy into light energy.