Explain the basic principles for producing laser beam.
Answers
In lasers, photons are interacted in three ways with the atoms:
Absorption of radiation
Spontaneous emission
Stimulated emission
Absorption of radiation
Absorption of radiation is the process by which electrons in the ground state absorbs energy from photons to jump into the higher energy level.
The electrons orbiting very close to the nucleus are at the lower energy level or lower energy state whereas the electrons orbiting farther away from the nucleus are at the higher energy level. The electrons in the lower energy level need some extra energy to jump into the higher energy level. This extra energy is provided from various energy sources such as heat, electric field, or light.
Let us consider two energy levels (E1 and E2) of electrons. E1 is the ground state or lower energy state of electrons and E2 is the excited state or higher energy state of electrons. The electrons in the ground state are called lower energy electrons or ground state electrons whereas the electrons in the excited state are called higher energy electrons or excited electrons.
Absorption of radiation is the process by which electrons in the ground state absorbs energy from photons to jump into the higher energy level.
In general, the electrons in the lower energy state can’t jump into the higher energy state. They need sufficient energy in order jump into the higher energy state.
When photons or light energy equal to the energy difference of the two energy levels (E2 – E1) is incident on the atom, the ground state electrons gains sufficient energy and jumps from ground state (E1) to the excited state (E2).
The absorption of radiation or light occurs only if the energy of incident photon exactly matches the energy difference of the two energy levels (E2 – E1).
To produce a laser beam we should have a light of high frequency i.e red light