Laser safety

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Laser safety

• Paul van Kampen
• 31/01/07

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Almost all you need to know about laser safety

• Beware of electrical safety
• Dont expose your eyes or skin
• Wear goggles
• Beware of water leaks
• Use warning signs
• Use interlocks

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Types of laser

• Continuous wave (cw) or pulsed
• Power
• Wavelength
• Visible/invisible
• Effect on skin

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Laser classification (1)

• Class I safe (UNFOCUSSED!)
• Class II safe - your aversion to bright light
  will protect you
• Class IIIA cw 1-5 mW, safe unless you look at
  it,or its reflection, directly
• Class IIIB cw 5-500 mW, pulsed lt10 J/cm2,
  sometimes diffuse reflection hazard
• Class IV cw gt500 mW, pulsed gt10 J/cm2, diffuse
  reflection, fire, skin hazard

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Laser classification (2)

• What is it based on?
• Cumulative ocular damage assumed linear lt3h
• Total energy of 3.85 mJ is safe
• Example class I laser limit
• Fully dilated pupil radius of 7 mm, area 0.385
  cm2
• Must be safe over 3 h 104 s
• Maximum Permissible Exposure (MPE)

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UV lasers

• Excimer lasers gas premix typically contains 0.1
  percent of fluorine/chlorine
• ArF, KrCl, KrF UV-C radiation
• Eye snowblindness
• Skin sunburn, skin cancer
• XeCl UV-B radiation
• Eye snowblindness
• Skin skin aging, increased pigmentation
• XeF, NdYAG tripled UV-A radiation
• Eye cataracts
• Skin skin burn, pigment darkening

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Visible/IR lasers

• CW/pulsed
• protect your eyes
• blue/-green worse than red-infrared
• dont shoot at your skin
• Dye lasers dyes are carcinogens
• CO2 lasers fire hazard

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Good lab design

• Often a competition between hazards
• Water
• Electrical
• Trip
• Laser radiation
• Scatter
• Direct exposure
• Good management is mostly common sense

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A laser lab (1)

• Data
• Vacuum chamber
• Pulsed IR class IV laser
• Target 10 cm behind glass
• Target 1.5 m above floor
• Lens F.L. 20 cm
• Lens holder aluminium
• Can you do better?

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A laser lab (2)

• Beam height
• Unsafe for people gt5 ft
• If you cant adjust target, move beam out of the
  way
• Door
• Dont shoot laser in that direction!
• Make sure the system is interlocked door open,
  laser off

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A laser lab (3)

• Lens
• Beware of scatter
• Each surface reflects 4 as a mirror (back into
  laser!)
• AR coating
• Turn lens around
• You may hit lens holder
• Spray paint black
• Window
• 4 reflection focused on lens

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A laser lab (4)

• Adaptability
• Cant easily adjust beam
• Tripping
• Water/electrical leads all over the floor
• Invisibility
• Can you mount a collinear visible alignment
  laser?

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A laser lab (5)

• Possible solution
• Collinear weak visible laser
• Shorter FL lens, turned
• Piped beam
• Mirrors allow manipulation
• Laser against wall
• Beware of pushing against piping