1. A short introduction on how “lasing” is achieved
LASERS
A short introduction on how
“lasing” is achieved

2. Applications of Lasers
To annoy people at the movies
Lasers in Industry
Lasers in Geography
Lasers in Astronomy
Lasers in Communication

3. 3 ways radiation interact with the energy levels of atoms
Spontaneous Emission
atom*  atom + photon
Induced absorption
atom + photon  atom*
Induced/stimulated emission
Responsible for laser creation
Atom* + photon  atom + 2photons
2 photons travel in exactly the same direction with the same energy and in phase

4. Importance of Induced Emission
Laser = Light Amplification by Stimulated Emission of Radiation
Simple Model
Why won’t this work?
Population Inversion
More atoms in upper/excited state than lower state
Done by pumping the ground states to excited states
Once pumped – decay rapidly (sp. em) to a metastable state
More atoms in a metastable state than ground state
Achieves population inversion

5. Lasing Transition Can happen once population inversion is maintained
Transition from metastable state to the ground state
Atom* + photon  atom + 2photons

6. 3 level laser
Ruby laser
1960 by
Theodore Maiman

7. 4 level laser
Relieves population inversion difficulty

8. Summary
How A laser Works