Transcript Introduction to laser safety

Imperial College Safety Unit - Introduction to laser safety - 1
Introduction to
laser
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What is a laser?
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The word “laser” is an acronym which stands for Light
Amplification by Stimulated Emission of Radiation.
Light energy is amplified to extremely high intensity by a
process called stimulated emission.
The energy generated by the laser is in or near the
optical portion of the electromagnetic spectrum.
How does a laser work?
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Electrons surrounding atoms are excited into higher
energy states to create a “population inversion”.
The excited electrons release their energy in the form of
photons which can, in turn, collide with other excited
electrons and cause them to release an identical photon
- this is called stimulated emission.
As more energy is put in so more photons are released.
By reflected the photons back and forth in a mirrored
system the amount of energy can be increased.
Some of the energy is allowed to escape through a
partially coated mirror to create a “laser beam”.
Types of laser
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Gas lasers
• including He-Ne and carbon dioxide lasers
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Dye lasers
Solid state lasers
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• including neodymium-YAG (Nd:YAG) lasers
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Semiconductor lasers
• diode lasers
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Chemical lasers
Laser light
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Laser light has the following properties:
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it is monochromatic
it is very intense
it has low divergence
it is coherent.
Lasers can have different types of beam output
• continuous wave (CW), or
• pulsed.
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Laser “speckle” is caused by scattered laser radiation
interfering with incident laser radiation.