Working with Lasers Deakin University Working with Lasers

Working with Lasers Deakin University

Working with Lasers Part 1: Background information Part 2: Laser hazards to consider Part 3: Laser classification Part 4: Laser safety Part 5: Lasers at Deakin

Part 1: Background Information • How lasers work • Why they are hazardous

How Lasers work • • Laser Material (gas, liquid, solid, semiconductor) Pump/Excitation Mechanism (discharge, flashlamp, laser) Feedback Mechanism (mirror) Output coupler (semi-transparent mirror)

Why Lasers Are Hazardous Laser light differs from light from other sources in several ways: – Monochromatic (single wavelength) – Directional (Low Divergence) – Coherent Laser light can pose an extreme hazard because a lot of energy is concentrated in a small area

Why Lasers Are Hazardous 2 Main Factors 1. Collimation Effects : Collimated light means the photons emitted from the laser are in parallel not scattered like conventional light sources. Therefore more light can be introduced into the eyes compared to other light sources.

Why Lasers Are Hazardous 2 Main Factors 2. Spot Size Effects : Radiation in the 400 – 1400 nm region is brought to a sharp focus on the retina. This can increase the radiant exposure (irradiance) by approx 100, 000 times.

Part 2: Laser Hazards to Consider 1. Beam Hazards • Damage to the eye • Damage to the skin 2. Non-Beam Hazards • Electrical safety • Chemical safety • Airborne contaminants • Noise safety

Beam hazards. Effects on Eyes and Skin by wavelength

Non-beam Hazards: Chemical § Laser dyes – most dyes are carcinogenic § Insulation Materials – Dusts, Fibres (Wear Masks) § Optical Fibers – Eye hazards § Solvents – flammability

Non-beam Hazards: Electrical • High voltages – Always ensure covers are in place. • 240 v – No uninsulated connections permitted. • Don’t leave live circuits unattended.

Non-beam hazards: Gases § Compressed gases – toxicity, flammability and asphyxiation hazards. § Vacuum system – implosion issues with glass vessels. Safety glasses must be worn.

Non-beam hazards: Cryogenics § Liquid nitrogen – cold burns and asphyxiation hazard. § Liquid N 2 can condense O 2 from the atmosphere and may cause an explosion. § Ensure you have been trained in the correct way to handle liquid N 2. § Do not accompany full Liquid N 2 Dewars in Lifts.

Non-beam hazards: Laser Generated Air Contaminants • Laser cutters can generate hazardous dust particles • Familiarise yourself with any potential by-products • Consult MSDS, reference books and supervisors • Use adequate extraction

Lab Hazards Combinations Toxic Gases Laser Beam 200 W Vacuum System High Voltage 40 k. V High Temp 800 C UV from Discharge Ionising Radiation Water Cooling Insulation Materials Oil Cooling (Hot Oil)

Part 3: Laser Classification

Factors affecting Laser classification level 6 main factors to consider: - Wavelength - Continuous Wave or Pulsed Operation - Power or Pulse Energy - Repetition Rate (PRF) - Beam Diameter & Profile - Beam Divergence

Laser Classification System Approx. Power Limits for CW Visible Wavelengths Only Class 4 Unsafe for eyes Unsafe for skin 0. 5 W Class 3 B Unsafe for eyes Generally safe for skin 5 m. W Class 3 R Safe with (0. 25 s. ) aversion response no viewing aids 0. 5 W Class 2 M Safe with no viewing aids Visible wavelengths only 1 m. W Class 2 Visible wavelengths only 0. 5 W 220μW to 0. 4μW Class 1 M Class 1 Safe with (0. 25 s. ) aversion response including viewing aids Safe with no viewing aids No precautions required

Old Laser Classification System Approx. Power Limits for CW Visible Wavelengths Only Class 4 0. 5 W Class 3 B 5 m. W Class 3 A 1 m. W Class 2 Visible wavelengths only Unsafe for eyes Unsafe for skin Unsafe for eyes Generally safe for skin Safe with (0. 25 s. ) aversion response no viewing aids Safe with (0. 25 s. ) aversion response including viewing aids 220μW to 0. 4μW Class 1 No precautions required

Laser Safety Precautions by classification Class 1 Lasers : - Safe Class 1 M Lasers: - No viewing aids Class 2 Lasers : - Safe with aversion response (No staring) Class 2 M Lasers: - Safe with aversion response (No staring); No viewing aids Class 3 R Lasers : (also old Class 3 A lasers) - No Staring, No viewing aids, Unsafe outside visible range

Laser Safety Precautions by classification, cont. Class 3 B Lasers : - Unsafe for eyes, generally safe for skin Class 4 Lasers : - Unsafe for eyes, unsafe for skin

Part 4: Laser safety

General Laser Lab Safety § Never directly view a laser beam. § Never point a laser pointer at a person. § Never over-ride interlocks § Never remove covers from equipment without approval from supervisors – laser, high voltages and other hazards are present.

General Laser Lab Safety, cont. § Clothing: Long sleeve clothing should be worn to protect skin. Wear enclosed footwear in labs. § Jewelry: watches & rings which could reflect beams should not be worn. § Viewing Aids: Never use microscopes, telescopes, magnifying glasses etc to view laser beams

Special Considerations for Class 3 B & 4 Lasers • Avoid Exposure of eyes & skin • Work in Controlled Areas • Diffuse Reflections are Hazardous • Use Beam Stops • Use Eye Protection • Post Warning signs • Interlocks Required

Laser Lab design § A labyrinth style entryway into labs, giving a safe area to put on safety equipment (PPE). § A storage rack for laser safety eyewear (labelled with wavelengths etc). § Laser operators should not be seated at beam height to avoid possible exposure

Laser hazard controls Hierarchy of controls Ø Ø Ø Elimination Substitution Isolation Engineering Administration PPE

Laser Controls Engineering • • • Protective Housings Remote Interlocks Access Panels Master Switches Enclosed beam baths

Laser Controls Administrative • • • Laser Safety Officer Safe Working Procedures (SWPs) User registration Record keeping Correct Labelling of device and area Medical surveillance (Eye tests) Laser Warning signs

Medical Surveillance > Eye testing before and after the use of Class 3 B & Class 4 lasers is recommended Visual acuity Ishihara test Amsler Grid

Laser Controls PPE The main form of protective equipment is protective eyewear, but when using Class 4 lasers protective clothing and footwear must also be worn

Eye protection > Ensure the correct wavelengths are covered (not all safety eyewear materials are the same) otherwise the safety goggles may be offering no protection for the laser you are working with

A note about Eye safe lasers Lasers with emission wavelengths longer than 1400 nm are often labelled as ‘eye-safe’ because wavelengths greater than 1400 nm are strongly absorbed in the cornea & lens of the eye rather than the relatively more sensitive retina. High powered or pulsed lasers at these wavelengths will still burn the cornea and cause severe eye damage. Corneal injuries are very painful. A laser labelled eye-safe should be treated the same as any other laser – with extreme caution. NEVER stare at a laser beam.

Part 5: Lasers at Deakin § Majority of lasers are Low Power, Class 1 & § § 2 Laser Pointers Laser, Chemical and Electrical safety procedures must be followed No Laser use after hours or by untrained personnel

Deakin laser procedures § All work should be covered by a Project Safety § § Plan which has been signed off by a lab manager and the University Radiation Safety Officer A Laser Hazard Identification checklist must be completed for Laser classes 3 and above Class 3 B and Class 4 lasers should have a written Safe Working Procedure on hand – guidelines available

Laser pointers are effective tools when used properly. The following considerations should be observed when using them: • Use only laser pointers with AS/NZS 2211 classification Class 1 or Class 2. • Do not use or purchase a laser pointer that has a stated emission level of greater than 1 m. W • Ensure Class 2 lasers are labelled correctly "Caution: Laser Radiation. Do not stare into the beam. Class 2 Laser Product. " • Never look directly into the laser beam. • Never point a laser beam at a person. • Do not aim the laser at reflective surfaces. • Do not allow children to use laser pointers.

Conclusion § Consider all the implications of your laser use, including those around you. § Never stare at a laser beam § Always wear correct Laser Safety Glasses § Report any lab problems or concerns to your supervisor and/or the University radiation safety officer