Optoelectronics and Photonics - LASER Safety

LASER: Light Amplification by Stimulated Emission of Radiation

• Components:
  • Amplifying or gain medium
  • Pumping source
  • Optical cavity (mirrors)

LASER Light Characteristics

• Monochromaticity: Single color light within a narrow range of wavelengths.
• Coherence: Waves travel in phase.

Laser Safety - Hazards

• Skin Injury: Typically heals, but large area exposures can lead to infections.
• Eye Hazards: Most vulnerable, injuries more serious than skin injuries, occur at lower power levels.

Laser Wavelength Regions & Eye Absorption

• UV (100 nm - 400 nm):
  • UV-C (280 nm - 100 nm)
  • UV-B (315 nm - 280 nm)
  • UV-A (400 nm - 315 nm)
• Visible Light (700 nm - 400 nm)
• IR (700 nm - 1 mm):
  • IR-A (1400 nm - 700 nm)
  • IR-B (3000 nm - 1400 nm)
  • IR-C (1 mm - 1400 nm)
    • Absorption varies by wavelength:
  • Cornea: Middle-ultraviolet (180-315 nm)
  • Lens: Near-ultraviolet (315-390 nm), selected wavelengths (700 nm - 3000 nm)
  • Retina: Visible and near-infrared (400 nm - 1400 nm)

Eye Injury Types by Wavelength

• Ultraviolet (UV): Inflammation and pain in cornea/conjunctiva, cataracts.
• Visible: Retinal impairment.
• Infrared (IR):
  • IR-A: Retinal injury.
  • IR-B: Cornea burn, cataracts.

Focusing and Irradiance

• Parallel rays focus on the retina, increasing irradiance.
• Intrabeam viewing: Focusing causes a significant irradiance increase.

Laser Hazard Classifications

• Based on potential to cause eye and skin injury.
• NOHD: Nominal Ocular Hazard Distance

Laser Classes

• Class 2: Output power below $1 mW$, visible light only, considered safe for normal operation.
  • NOHD for a $0.99 mW$ laser is $46 ft (14 m)$.
• Class 3R: Output power between $1-5 mW$, small hazard potential.
  • NOHD for $4.99 mW$ laser is $104 ft (32 m)$.
• Class 4: Hazardous; can burn skin and materials. Significant eye injury risk.

Laser Equipment Examples

• Class 1: Safe in all operations (low output power).
• Industrial lasers (Class 3/4) can be enclosed to become Class 1 (embedded laser), e.g., laser printers.

Safety Rules For All Lasers

• Avoid direct beam/reflection viewing.
• Remove reflective surfaces.
• Control access to laser areas.
• Operate lasers under supervision of knowledgeable personnel (Laser Safety Officer - LSO).
• Report accidents immediately.

Causes of Laser Accidents

• Alignment (28%)

• High voltage (16%)

• Eyewear failure (16%)

• Non-beam hazards (12%)

• No eyewear (8%)

• Malfunction (8%)

• Accidental exposure (8%)

• Improper restoration after servicing (4%)

  Laser Safety Glasses

  • Optical Density (OD) is defined as: $OD = Log_{10} \frac{1}{T}$, where T is the transmittance.