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  • Laser Safety Training Course
  • Laser Output

    The output of a laser may be described as continuous or pulsed

     

    Continuous Wave (Figure 5)

    If energy is continuously pumped into the active medium an equilibrium may be achieved between the number of atoms raised to a meta stable state and the number of photons emitted resulting in a continuous laser output. Output for continuous wave lasers is expressed as Irradiance(E) which is the concentration of laser power incident on a given area or Power/Unit Area (W/cm2)

    Figure 5 -  Continuous Output

     

    Pulsed Lasers and Q-Switched Lasers (Figure 6)

    Pulsed laser emissions are produced when the excitation medium is modulated producing a pulse of laser radiation lasting usually less than 0.25 sec. Pulsed output may also be produced by blocking the beam with a rotating mirror or prism.

    Q-switching or Q-spoiling is a technique employed to produce a very high output pulse. Q- switching is accomplished by using a device to prevent the reflection of photons back and forth in the active medium. This produces a higher population of electrons in the meta stable state. At a predetermined instant the Q-switch is turned off allowing the lasing action to continue producing very intense short pulses of laser radiation. Q-switched lasers produce pulses of 10 to 250 nanoseconds (ns).


    Output for pulsed lasers expressed as Radiant Exposure (H) which is the concentration of laser energy on a given area Energy/Unit Area (J/cm2).

    Figure  6 - Pulsed Output

     

     

    Examples of Common Laser Types             

     Laser Type 

    Media

    Wave Length (s)

    Nanometres

    Excimer Gas Lasers Argon Fluoride (UV) 193 nm
      Krypton Chloride                  (UV) 222 nm
      Krypton Fluoride (UV) 248 nm
      Xenon Chloride                    (UV) 308 nm
      Xenon Fluoride                    (UV) 351 nm
    Gas Lasers Nitrogen                      (UV) 337 nm
      Helium Cadmium (UV) 325 nm
      Helium Cadmium    (Violet) 441 nm
      Argon         (Blue) 488 nm
      Argon   (Green) 514 nm
      Krypton       (Blue) 476 nm
      Krypton       (Green) 528 nm
      Krypton        (Yellow) 568 nm
      Krypton       (Red) 647 nm
      Xenon     (White) multiple
      Helium Neon  (Green) 543 nm
      Helium Neon  (Yellow) 594 nm
      Helium Neon  (Orange) 612 nm
      Helium Neon  (Red) 633 nm
      Helium Neon   (NIR) 1,152 nm
      Helium Neon  (MIR) 3,390 nm
      Hydrogen Fluoride  (MIR) 2,700 nm
      Carbon Dioxide (FIR) 10,600 nm
    Metal Vapour Lasers Copper Vapour (Green) 510 nm
      Copper Vapour           (Yellow) 570 nm
      Gold Vapour (Red) 627 nm
      Doubled Nd:YAG (Green) 532 nm
      Neodymium: YAG (NIR) 1,064 nm
      Erbium: Glass (MIR) 1,540 nm
      Erbium: YAG (MIR) 2,940 nm
      Holmium: YLF (MIR) 2,060 nm
      Holmium: YAG (MIR) 2,100 nm
      Chromium Sapphire (Ruby) (Red) 694 nm
      Titanium Sapphire (NIR) 840-1,100 nm
      Alexandrite (NIR) 700-815 nm
    Dye Lasers Rhodamine 6G (VIS) 570-650 nm
      Coumarin C30 (Green) 504 nm
    Semiconductor Lasers Gallium Arsenide (GaAs) (NIR) 840 nm
      Gallium Aluminium Arsenide (VIS/NIR) 670-830 nm