Gas Lasers

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Gas Lasers

• Light Amplification by Stimulated Emission of
  Radiation

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Introduction
Gas Lasers

• Lasing medium is made up of one or a mixture of
  gases or vapors
• Classified in terms of the type of transitions
  that lead to their operation atomic or molecular
• Most common is He-Ne laser - uses atomic
  transition to produce output light, also Argon
  laser
• Molecular gas lasers are CO, CO2, N2 lasers,
  excimer lasers
• Focus First gas laser developed by renowned
  scientist Ali Javan (Bell Telephone Laboratory)
  He-Ne laser

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Advantages of Gas Lasers

• High Volume of Activation Material
• The Materials are Inexpensive
• Not Easily Damaged
• Heat Can be Removed Easily

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Quantum Laser Processes

• Energy levels of atoms and molecules can have
  only certain quantized values
• Transitions between these quantized states occur
  by photon processes absorption, emission, and
  stimulated emission
• Transitions typically involve the absorption or
  emission of photons

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Helium-Neon Gas Laser

• Excited state life is very short 10-8 seconds
• He gas in the laser tube provides the pumping
  medium for population inversion
• Excited level of He20.61eV is close to a level
  in Ne20.66eV
• Upon He-Ne collision, energy is transferred from
  He to Ne atom

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• With Mirrors at the ends of the tube allow for
  the beam to gain intensity by stimulated emission
  of more photons at the same wavelength
• Operates in the red at 633nm, green at 544nm,
  and IR at 1523nm or 3391nm
• Used in laser light displays, bar code scanning,
  medical treatments regimentation

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Parts of the Argon Ion Gas Laser

• The laser medium - Argon Gas
• The Energy Pump - Electrical Discharge
• The Two mirrors that form the Resonator Cavity

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Stimulated Emission

• Electron already in excited state incoming
  photon with energy equal to the difference in
  levels
• Stimulates a transition to that lower level
  producing a second photon of the same energy

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Population Inversion

• Population inversion sets the stage for
  stimulated emission of multiple photons
• This is precondition for the light amplification
  in a laser
• Emitted photons have a definite time and phase
  relation to each other coherence

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The out put of the Argon Lasers

• The output wavelength are 514 nm (green) and 488
  nm (blue)
• The output power is 3 watts.
• The output is a continuous wave

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Applications

• Range finder (Measuring distance)
• Removes stains and tattoos
• Skin treatment
• Hair removal
• Cosmetic surgery

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Disadvantages

• Low efficiency
• Limited power out put
• Old technology