Laser categories

A laser source can consequently be classified with respect to ether one of the two following characteristics :

• The first classification compares laser sources for which temporal properties differ. One can distinguish continuous sources (corresponding to pulses longer than 0.25s, such as in the He-Ne case), and pulsed sources (gain-switched sources : τ= 10 µs to 0.1 s ; Q-switched sources : τ= 10 ns to 10 ps ; mode locked lasers : τ~1 fs to few 10 ps )

• The second classification compares laser sources for which the amplifying mediums differ. One can then distinguish four different gain medium classes :

  • Gaseous mediums, using for example neutral atoms ( He-Ne, He-Cd, ...), ions (Argon Ar+, Kryton Kr+), or molecules (C02, excimers ...)

  • Solid mediums, such as rubis (first historical laser), YAG...

  • dyes

  • semi-conductors