LASERS

1
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 wont 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