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) Laser is basically comprised of laser material, a pump, and mirrors 1. When pump is ON, photons are spontaneously emitted by the laser material as excited electrons return to lower energy levels 2. Photons reflect off mirrors and start to stimulate other electrons to emit their photons 3. A chain reaction begins and the laser begins to ‘lase’

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. A 1mW laser (could be classed as low as a Class 2 laser) will introduce 82,000 times more light into the eye than a 100W light globe!

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. A low power laser pointer (1mW) when viewed directly by the eye introduces 26 times more light than looking directly at the sun! Never stare at any laser!!

Part 2: Laser Hazards to Consider 2. Non-Beam Hazards Electrical safety Chemical safety Airborne contaminants Noise safety Beam Hazards Damage to the eye Damage to the skin Make sure both beam and non-beam hazards are considered when working with lasers

Beam hazards- Effects on Eyes and Skin by wavelength Eyes are most sensitive to laser damage. Different parts of the eye are susceptible to different wavelengths. Damage can occur from heating, photochemical reactions & explosive rupture. Effects include: Photokeratitis (Inflammation of the cornea) Cataracts Retinal Burns Erythema (Abnormal redness) Corneal Burns Degradation of Colour & Night Vision Thermal Skin Burns

Non-beam Hazards: Chemical Apart from laser hazards in labs, other hazards are usually present. Laser dyes, solvents, acids and other chemicals may be used which should be taken into consideration when designing lab safety precautions. Insulation materials may require the use of dust masks. 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. Another hazard is electrical, workers have been killed by excitation circuits. Experimental circuits are used in some labs, it is important to have these checked thoroughly by qualified personnel for safety. Don’t leave exposed live circuits in labs unattended.

Non-beam hazards: Gases Compressed gases – toxicity, flammability and asphyxiation hazards. Vacuum system – implosion issues with glass vessels. Safety glasses must be worn. Compressed gases and vacuum system pose yet another common lab hazard. Ensure that caution is taken working with gas piping and cylinders. Do not attempt to change gas bottles unless you have been instructed how.

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. Only handle if properly trained. Wear thick, insulated gloves and face/eye protection. Use in well ventilated areas. Asphyxiation -- nitrogen is not poisonous; air has about 78% nitrogen, 21% oxygen.   If sufficient liquid nitrogen is vaporized to reduce the oxygen below 19.5%, you are at risk of oxygen deprivation.  In a 3 x 3m unventilated lab only 6l of Liquid N2 would be required. Liquid N2 expands around 700x into a gas. Simple asphyxiants such as nitrogen do not have good warning properties!   You simply pass out without any warning and then die. Liquid Nitrogen has a boiling point of -195.8°C

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 With Laser cutting it is important to have an extraction systems in place and functioning correctly so as to catch all the contaminants produced. Extraction systems must be maintained, including regular cleaning, to ensure they function correctly.

Lab Hazards Combinations Toxic Gases Laser Beam 200W Vacuum System High Voltage 40 kV With most experiments and experimental equipment hazards are usually present in combinations. This picture of a Laser system is a good example of multiple hazards. High voltages & solvent/oil present a fire risk - High voltages & water present an electric shock risk High Temp 800C Water Cooling Insulation Materials UV from Discharge Ionising Radiation Oil Cooling (Hot Oil)

Part 3: Laser Classification

Factors affecting Laser classification level 6 main factors to consider: When you work with a laser it is very important to know the laser hazard class. Lasers are not classified based purely upon their energy: Wavelength, Pulse Repetition Frequency, Pulse Energy, Beam Diameter and Divergence are factors that play a part in laser classification by the Australian Standard 2211.1:2004 - 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 0.5W Class 3B Generally safe for skin 5mW Class 3R Safe with (0.25 s.) aversion response no viewing aids Class 2M Visible wavelengths only Safe with no viewing aids 1mW Class 2 Safe with (0.25 s.) aversion response including viewing aids Class 1M 220μW to 0.4μW Class 1 No precautions required When using Lasers in Australia, the Australian Laser Safety Standard AS2211:2004 should be followed. This is the current laser Classification System in force. New Classes of lasers have been included from the old classification system: Class 3R replaces 3A and Class 1M and 2M of note due to the higher powers allowed Classifying lasers is an involved process and is explained with examples in the Australian standard Note that the powers quoted can be used as a rough guide only- they are for CW (Continuous Wave) visible lasers only; pulsed lasers or those with wavelengths outside 400-700nm will have different power cut-offs for each Classification

Old Laser Classification System Approx. Power Limits for CW Visible Wavelengths Only Class 4 Unsafe for eyes Unsafe for skin 0.5 W Class 3B Generally safe for skin 5 mW Class 3A Safe with (0.25 s.) aversion response no viewing aids 1 mW Class 2 Visible wavelengths only Safe with (0.25 s.) aversion response including viewing aids 220μW to 0.4μW Class 1 No precautions required This table shows the old Laser Classification System (AS/NZS 2211.1:1997). Some people may be familiar with these classes Notable here is that any lasers over 5mW are considered dangerous to the eyes. Note: Lasers classified in America will be noted as Class I, II, IIa, IIIa, IIIb, IV which is not directly transferrable to the current method of Australian laser classification

Laser Safety Precautions by 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 Although Classes 1, 1M, 2, 2M and 3R have little in the way of precautions, no laser above class 1 is safe to be stared at. Never stare at any laser beam or reflections. Remember that some lasers may still be labelled Class 3A from the old standard Viewing Aids- Any Optics (magnifying glass, microscope, telescope, etc.) that are used to focus and hence intensify the laser Aversion response- Also known as the blink reflex; Intentional suppression of the aversion response could lead to eye injury Note: Class 3R lasers are unsafe outside of the visible range (400-700nm) because they cannot be seen and hence there is no aversion response

Laser Safety Precautions by classification, cont. Class 3B Lasers : - Unsafe for eyes, generally safe for skin Class 4 Lasers : - Unsafe for eyes, unsafe for skin Class 3B & 4 Lasers are dangerous for the eyes and will cause damage if viewed Class 4 are dangerous for skin exposure also

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. Never directly view a laser beam. With Class 3B & 4 Lasers diffuse reflections can be a hazard. Even when some lasers are switched off and plugs removed from wall sockets, excitation circuits, capacitors can still retain a charge.

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 Clothing: It is recommended watches and rings are removed and long sleeved clothing is worn when working with higher powered lasers. Viewing Aids: Viewing a laser using viewing aids can magnify the laser beam and cause significant eye damage.

Special Considerations for Class 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 The following considerations should be made by users of Class 3B & Class 4 lasers: -Avoid any eye exposure to laser beam (also skin exposure for Class 4) -Laser to be contained in a Controlled area, with only trained staff and students having access (enclosed beam if possible) -Specular (shiny, reflective surfaces) and diffuse (dull, non-reflective surfaces) reflections must be considered as they are hazardous -Beam Stops are used to prevent inadvertent exposure; they ensure beam paths are terminated at end of useful length Use CORRECT eye protection if exposure is possible, with good room illumination (causes pupil dilation) Warning Signs used and in place -Remote Interlocks connected to Room and Door Circuits -Laser can be Key Controlled – Key is removed when laser not in use. -Emission indicator Lights used -Lasers are registered with the University; SOPs and manuals are on hand in immediate area

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 It is good practice to have a labyrinth style entryway into laser areas. This area is useful as an eye safe space to store and put on personal protection equipment (PPE) before entering the hazard area. All reflective surfaces in the laser lab should be removed or covered to prevent unsafe reflections

Laser hazard controls Hierarchy of controls Elimination Substitution Isolation Engineering Administration PPE Consideration should be given in this order to controlling the laser hazard. PPE is the LAST option to consider!

Laser Controls Engineering Protective Housings Remote Interlocks Access Panels Master Switches Enclosed beam baths Hierarchy of Controls: Elimination Substitution Isolation Engineering Administration PPE

Laser Controls Administrative Laser Safety Officer Safe Working Procedures (SWPs) User registration Record keeping Correct Labelling of device and area Medical surveillance (Eye tests) Hierarchy of Controls: Elimination Substitution Isolation Engineering Administration PPE Laser Warning signs

Medical Surveillance Eye testing before and after the use of Class 3B & Class 4 lasers is recommended Eye examinations are recommended for operators of high powered lasers to check that no damage is being done to eyes. Checks should be done before lasers are first used, when ceasing employment and after a suspected exposure. Recommended tests include: Ocular history General health Visual acuity Ishihara test or Farnsworth D15 test Amsler grid Contact the Deakin Radiation Safety Officer for details. 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 Hierarchy of Controls: Elimination Substitution Isolation Engineering Administration PPE

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 lasers must be on the University laser register 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 safety information is available from the University Radiation Safety Officer, Matthew Connolly (x71370)

Laser pointers 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 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 When choosing eyewear, be sure that they are for the correct wavelengths and have enough optical density to protect you. Always consider all the implications of your project, for you and those around you. Regarding any safety issues, please talk to your supervisor, lab safety officer or the University Radiation Safety Officer (Matt Connolly x 71370)