Working with Lasers

Deakin University

Working with Lasers

Part 1: Background informationPart 2: Laser hazards to considerPart 3: Laser classificationPart 4: Laser safetyPart 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 HazardousLaser 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 – 1400nm 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 N2 can condense O2 from the atmosphere and may cause an explosion.

Ensure you have been trained in the correct way to handle liquid N2.

Do not accompany full Liquid N2 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

High Voltage40 kV

Water Cooling

Insulation Materials

Oil Cooling(Hot Oil)

Laser Beam200W

Vacuum System

High Temp 800C

Ionising Radiation

Toxic Gases

UV from Discharge

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

Approx. Power Limits for CWVisible Wavelengths Only

Class 4 Unsafe for eyesUnsafe for skin

0.5W Class 3B Unsafe for eyesGenerally safe for skin

5mW Class 3R Safe with (0.25 s.) aversion response no viewing aids

0.5W Class 2MVisible wavelengths only

Safe with no viewing aids

1mW Class 2Visible wavelengths only

Safe with (0.25 s.) aversion response including viewing aids

0.5W Class 1M Safe with no viewing aids

220μW to 0.4μW

Class 1 No precautions required

Laser Classification System

Old Laser Classification System

Approx. Power Limits for CWVisible Wavelengths Only

Class 4 Unsafe for eyesUnsafe for skin

0.5 W Class 3B Unsafe for eyesGenerally safe for skin

5 mW Class 3A Safe with (0.25 s.) aversion response no viewing aids

1 mW Class 2Visible wavelengths only Safe with (0.25 s.) aversion

response including viewing aids

220μW to 0.4μW

Class 1 No precautions required

Laser Safety Precautionsby classification

Class 1 Lasers : - Safe

Class 1M Lasers: - No viewing aids

Class 2 Lasers : - Safe with aversion response

(No staring)

Class 2M Lasers: - Safe with aversion response

(No staring); No viewing aids

Class 3R Lasers : - No Staring, No viewing aids,

(also old Class 3A lasers) Unsafe outside visible range

Laser Safety Precautionsby classification, cont.

Class 3B 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 forClass 3B & 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 controlsHierarchy of controls Elimination Substitution Isolation Engineering Administration PPE

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

Laser ControlsAdministrative• 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 3B & Class 4 lasers is recommended

Visual acuity Ishihara test Amsler Grid

Laser ControlsPPE

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 1400nm are often labelled as ‘eye-safe’ because wavelengths greater than 1400nm 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 3B and Class 4 lasers should have a written Safe Working Procedure on hand – guidelines available

Laser pointersLaser 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 1mW

• 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