Laser Principle

  • Karl F. RenkEmail author
Part of the Graduate Texts in Physics book series (GTP)


A laser (=laser oscillator) is a self-excited oscillator. A self-excited oscillator starts oscillation by itself and maintains an oscillation. Laser radiation is generated by stimulated transitions in an active medium. The active medium is a gain medium — propagation of radiation in the active medium results in an increase of the energy density of the radiation. The active medium in a laser experiences feedback from radiation stored in a laser resonator. A portion of radiation coupled out from the resonator represents the useful radiation.


Active Medium Occupation Number Round Trip Gain Factor Lower Laser Level 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.Institut für Angewandte PhysikUniversität RegensburgRegensburgGermany

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