Homebrew Lasers

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					Homebrew Lasers

        Florian Gahbauer

OSA Latvia Student Chapter Seminar
        November 5, 2007
I myself have never made or attempted to make any of
the devices described in this presentation or anything
like them. Everything that I know about this devices I
learned from the internet. Thus, I cannot guarantee the
accuracy or safety of the designs. The purpose of this
presentation is to present interesting ideas and perhaps
stimulate future projects, but anyone attempting to
realize these projects will have to take responsibility for
their own safety.

At the same time, I have tried to give credit where credit
is due, by including links. I apologize, if I have failed to
acknowledge any sources of information.
Construction and operation of any laser device is
hazardous. Do not attempt to construct or operate a
laser without adequate safeguards and safety practices.
Most lasers involve high voltages, toxic chemicals, high
vacuum, laser radiation and other hazards. The author
specifically disclaims any and all liabilities associated
with the construction and use of such devices. Designs
presented here are in the interests of providing
information on operational principles only and do not
represent safe nor ANSI safety compliant designs.
•   Basic principles of lasers
•   The Nitrogen TEA Laser
•   Different examples of N2 TEA Lasers
•   High Voltage supplies
      Basic Principles of Lasers (1):
          Population Inversion
      Basic Principles of Lasers (2):
          Stimulated Emission
     Typical Laser Schematic
           The TEA Nitrogen Laser
                                               • Medium: Nitrogen gas (N2)
                                               • Pump: electric discharge
                                               • Resonator: not needed
   N2 TEA Laser Schematic
N2 Laser Circuit Schematic
 Advantages of the TEA N2 Laser
• Can operate in air (72% nitrogen)
• No optics required
  – Amplification of nitrogen is very high
  – Significant reduction in cost and complexity
• No vacuum required
• Parts are generally inexpensive
Disadvantages of the TEA N2 Laser
• Timing of spark pulse is critical: ns
  – Upper state lifetime: t[ns] = 36/(1+P[torr]/58)
• Beam profile is not so good and small
  – Hard to use as dye laser pump (1.5mm-2mm)
• Light output is in UV (337.1 nm)
  – (but fluorescence visible on paper)
• Some people recommend the N2 laser in
  – Less critical electronic requirement
                  Possible Parts List
                                           + HV supply
Nitrogen Laser by Thomas Rapp
  Prof. Csele’s Basic TEA Laser
Improved TEA Laser by Prof. Csele
Jarrod Kinsey’s TEA Laser
        Some Critical Issues
• Timing of discharge circuit
  – Must be very fast (<2.5 ns at P=1atm)
  – Therefore, must avoid stray inductance in
• Alignment of Electrodes
  – Electrodes must be aligned to within
    micrometers (according to one source)
• Smoothness of Electrodes
  – Electrodes must be smooth to avoid
    discharges at sharp edges
Prof. Csele’s Nitrogen Laser
 Nitrogen TEA Lasers in Operation
• Tour of Homemade TEA Laser
• Rapid-firing TEA laser
         High Voltage Supplies
•   Laboratory High Voltage Supply
•   Laser printer HV supply
•   Ignition coil circuit
•   Fly-back transformer (from TV) circuit
•   Electrostatic generator
•   Flash transformer (from disposable
    camera)/Cockroft-Walton multiplier
    – Caution: Camera flash circuits can store
      dangerous amounts of energy in capacitors
Fly-back Transformer

Fly-back Transformer Circuit
                     Ignition Coils

 E  ds   dt
                 Ignition Coil Circuit
           Cockroft-Walton Multiplier

    Eout  2 * Eac * N stages
 Cockroft-Walton Multiplier and
   Neon Sign Transformer
   Electrostatic Generator

• Laser radiation
  – 337.1 nm is in UV, i.e., invisible
• High Voltage
  – 20 kV but only a few mA
  – Careful of energy stored in capacitors
• Spark Gap
  – UV
  – Noise: noise can be more damaging than it sounds.
    Enclose the spark gap or use ear protection
• Professor Csele’s Site

• Sam’s Laser FAQ

• Jarrod Kinsey’s Site

• Thomas Rapp’s Site
More Information

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