A short introduction on how “lasing” is achieved LASERS A short introduction on how “lasing” is achieved
Applications of Lasers To annoy people at the movies Lasers in Industry Lasers in Geography Lasers in Astronomy Lasers in Communication
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
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
Lasing Transition Can happen once population inversion is maintained Transition from metastable state to the ground state Atom* + photon atom + 2photons
3 level laser Ruby laser 1960 by Theodore Maiman
4 level laser Relieves population inversion difficulty
Summary How A laser Works