UC Santa CruzLaser Safety Training

Acknowledgements UCRRick MannixLaser Safety Officer

Karen Janiga, MSRadiation Safety OfficerLaser Safety Officer

Janette De La Rosa Ducut, Ed.D.Training Manager

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1. Determine laser classes and components

2. Identify hazards Biological Non-Beam

3. Implement controls Engineering Administrative Work Practice PPE

Objectives

Light

Amplification by

Stimulated

Emission of

Radiation

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LasersIntense light that can cause tissue damage, burns, and damage to the eye and skin.

What is a Laser?

Ordinary light is incoherent, visible, dispersed, and low powered.

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Laser light is different from ordinary light, like the type you find in a light bulb. Ordinary light is incoherent. This means that it has many wavelengths, that move in many directions, and thus can emit many different colors. This results in light that has a low concentration of power per surface area.

Light Properties

Laser light is coherent, sometimes invisible, directional, and high powered.

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In contrast, laser light is coherent. This means that the light rays have the same wavelength (that move in unison), travel in one direction, and have one specific color of light (or what is known as “monochromatic”). This results in a narrow laser beam that has a high concentration of power per surface area.

Laser Properties

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Laser Components• All lasers have three common elements: a pump, a lasing medium,

and an arrangement of two mirrors.

• The pump produces energy used to excite the lasing medium, and controls the laser's output power. Examples of energy sources include flash lamps, electricity, chemical reactions, and other lasers.

• The lasing medium is a substance that emits coherent light as the result of exposure to the pumping system.

• Two mirrors form a feedback mechanism. When light is bounced back and forth between the mirrors, its energy is amplified (hence the term “stimulated emission”). The amplified light escapes from the partially transmitting mirror (also known as the “optical resonator”), resulting in an actual laser beam.

Pump

Lasing Medium

MirrorReflectant

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MirrorTransparent

Laser Components

Output

Continuous

Pulsed

> ¼ sec

< ¼ sec

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Lasers also differ from each other based on their output characteristics. They can be a continuous wave or a pulsed laser

beam.

Output

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Continuous wave lasers emit beams at a constant power (similar to a flashlight) for at least ¼ of a second. This is enough time for

serious eye damage, if the laser has a high enough power. Power for these lasers is expressed in the form of Watts.

Continuous

> ¼ sec

Output

< ¼ sec

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Pulsed lasers emit beams in a single pulse, or train of pulses for a period less than ¼ of a second. If you’re struck in the eye by

one pulse, you are unlikely to be struck by a second pulse due to this time gap. However, pulsed lasers are usually more

hazardous than continuous lasers because the peak power for each pulse can be very high, causing biological damage to the

eyes and skin. Energy for these lasers is expressed in the form of Joules per second.

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BEAM DIVERGENCE

LASER d

r

f

f =dr

If the beam is 1 foot in diameterwhen it hits a wall 1000 feet away,

the beam divergence angle is:

f = 1 ft1000 ft

= 0.001 radian

= 1 mrad

Laser-Professionals.com

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Some mathematics covering physical features of a laser beamFollow this slide

BEAM DIVERGENCEThis allows us to calculate the energy or power density at any distance

IRRADIANCE CALCULATIONThis illustrates the change in power density introduced by a focusing lens

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BEAM DIVERGENCE

LASER d

r

f

f =dr

If the beam is 1 foot in diameterwhen it hits a wall 1000 feet away,

the beam divergence angle is:

f = 1 ft1000 ft

= 0.001 radian

= 1 mrad

Laser-Professionals.com

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IRRADIANCE CALCULATION

The diameter is reduced by a factor of 100.

The irradiance is increased by a factor of 10,000.

IRRADIANCE OF FOCUSED SPOT:

E2 = 250,000 watts/cm2

Power Irradiance =

Area p D2

Area = 4

20 Watt Laser

D1 = 1 cm D2 = 0.01 cm

IRRADIANCE AT LENS:

20 watts

(3.14)(1cm)2/4

E1 = 25 watts/cm2

E1 =

Laser-Professionals.com

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1/e2 = 0.135

AverageIrradiance

PeakIrradiance

d1/e2

d1/e1/e = 0.368

BEAM DIAMETER

Laser-Professionals.com

63%

86.5%

99%

Gaussian beam shape

d1/e =2

d1/e2

Semiconductor

Diode

Liquid Dye

SolidRubyNd:YAGTi:Sapphire

GasHeNe ExcimerArgon

Physical State

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Lasers differ from each other based on the kind of lasing

medium they use. This medium can be a gas (such as Argon),

solid-state (such as Ruby crystal), liquid (or a dye), or

semi-conducting material (such as a diode).

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Laser Classification

- Class 1- Class 1M - safe for viewing

without optics- Class 2- Class 2M- hazardous if

viewed with optical aids- Class 3R – used to be called

3A- Class 3B- Class 4

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Class 1 LaserPower output is too low to cause eye or skin injury

Examples:

- power = few microwatts

- high-powered expanded beam

A class 1 product is a totally contained laser system, does not present a hazard during normal operation.

The goal of laser safety is to have every laser set up a class 1 product.

A class 1 product will contain a higher class laser

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Class 2 Laser

- Output less than 1 milliwatt in visible range (400-700nm).

- If struck in the eye by a Class 2 laser, one will normally

blink or turn away. This reflex takes less than one quarter

of a second, which is adequate time to protect the eye.

- Since the eye must see the light to cause the blink reflex,

there are no Class 2 lasers that emit invisible wavelengths.

- Can be a hazard if the aversion response is overridden or

slowed

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Class 3R Laser (formerly 3A)

- Safe for momentary viewing- Can be visible or invisible (Only visible for commercial products)- Between 1-5 mW- Can be a hazard if momentary viewing is through optics capable of collecting enough energy from a large diameter beam and focusing it onto the eye.

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Class 3B Laser

- Visible or invisible- Intra beam viewing hazard- Specular reflection hazard- CW output between 5-500 mW- Pulse limit cannot produce 125mJ in less than 0.25 s

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Class 4 Laser

- Pose greatest danger- Any output higher than Class 3B- Intra beam viewing hazard- Specular reflection hazard- Possible Diffuse reflection hazard- Fire hazard

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Non-Classical Lasers

Non-linear optics-Harmonic generation of light waves at integral multiples of the frequency

of the original wave.

-You may have to protect yourself simultaneously from multiple wavelengths, depending upon the circumstances.

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Biological Effects

XeCl gas excimer

When used improperly, lasers can cause injuries. The organs affected by exposure to are the eyes and skin. Some lasers can cause delayed effects after low-level exposures over long time periods (perhaps even for years). Most effects, however, are immediate following acute, brief exposures, lasting seconds or even much less.

Examples of two very dangerous lasers include the XeCl gas excimer which causes cataracts in the eyes, and the Nd:YAG Invisible laser which causes

most skin injuries.

180 280 315 400 7001400

3000

UV-C UV-B UV-A

Ultraviolet Visible Infrared

IR-A IR-B IR-C

Photokeratisis(200 – 315 nm)

Photochemical Cataracts(315 – 400 nm)

Thermal retinalinjury

(315 – 400 nm)

Cataracts(750 – 1400 nm)

Corneal burn(1400 – 1,000,000 nm)

Cornea

Lens

Retina

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Biological Effects

180 280 315 400 700 1400 3000

Biological Effects

UV-C UV-B UV-A

Ultraviolet Visible Infrared

IR-A IR-B IR-C

Blue Light Hazards• Do not stare at sun,

welding arcs, or blue lamps • Prevent lengthy exposures

greater than 10 seconds• Beware of delayed

appearance (24-48 hours)

Photobleaching(400 – 500 nm)

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Biological EffectsUltraviolet Radiation

• 180 - 400nm (damages cornea and lens)• Hazardous Properties

– Invisible to eye– Delayed sensation effect– Chronic health effects (cataracts)

• If you are taking a medication and working around UV laser light, you should check to see if the medication will make you photosensitive.

180 280 315 400 700 3000

UV-C UV-B UV-A

Ultraviolet Visible Infrared

IR-A IR-B IR-C

Biological Effects

IntrabeamViewing

SpecularReflections

Diffuse Reflections

Direct viewing

Flat Surface (mirror like)ex: plastic, glass

Rough Surface(diffusion)ex: table top

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SpecularReflections

Diffuse Reflections

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Flat Surface (mirror like)ex: plastic, glass

Rough Surface(diffusion)ex: table top

Biological Effects

Lasers that have shorter wavelengths (such as those in the UV region up to 315 nm) easily disperse off of rough surfaces through diffusion. In contrast, lasers that have longer wavelengths (such as those above 315 nm) tend to disperse easily off

of flat surfaces through specular reflection.

Check for eye injury See: Flash and after-

image in opposite color OR difficulty detecting blue or green colors

Feel: Burning pain on cornea

Hear: “Pop” sound

Before After

Signs and Symptoms

Colors

180 280 315 400 700 1400 3000

Biological Effects

UV-C UV-B UV-A

Ultraviolet Visible Infrared

IR-A IR-B IR-C

Accelerated AgingIncreased Pigmentation

(280 – 315 nm)

Eurythema and Cancer(200 – 315 nm)

Burns and Pigment Darkening(315 – 400 nm)

Burns and Photosensitive reactions(400 – 780 nm)

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Emergency Procedures

Disable machineTurn off, unplug, and post sign

Seek medical attentionTreat minor skin damage with first aid OR transport major skin or any eye injuries to medical facility

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Electrical HazardHigh voltage risk • Eliminate contact with

high voltage• Arrange for repairs• Lockout / Tagout• Inspect cords and plugs• Ground all equipment• Complete training

Non-Beam Hazards

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Many lasers have high voltage power supplies that can present a risk of electrocution unless

sufficient care is taken when servicing them. Thus, ensure that you eliminate any contact with high voltage equipment.

Do not perform electrical service or maintenance on a laser unless you are properly trained. Allow the experts, including the service representatives for the laser manufacturer, or the campus electricians, to make any necessary repairs.

When there are known issues with equipment, lockout or tagout the equipment until it is safe to use.

Make sure that you inspect cords, plugs, and accessories for missing or damaged wiring. Look for shorts and overheated components. Do not overload circuits / outlets, place near water, or wear metal objects around electrical equipment.

Ground all equipment and complete training in basic electrical safety.

If personnel in your work area are working with high voltage power supplies, then Environmental Health & Safety recommends that you take a First Aid and CPR class.

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Non-Beam Hazards

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ElectrocutionEmergency Procedures

• Kill the circuit• Call 911• Use nonconductor to

remove victim• Initiate CPR (if trained)

Chemical (Liquid)Liquid phase dye lasersMay be carcinogenic or

mutagenic and require special precautions,

• Mix in fume hood• Wear PPE• Use secondary

containment• Review MSDS

Non-Beam Hazards

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Chemical (Gas)Excimers involve use oftoxic fluorine or chlorine gas

• Store in ventilated gas cabinets

• Use halogen detection and alarm systems or halogen gas scrubbers in rare cases

Non-Beam Hazards

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Chemical (Gas)Gases generate harmfulairborne contaminants• High powered lasers

can vaporize materials• Prevent from inhaling• Ventilate adequately• Use local exhaust

systems

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Non-Beam Hazards

FiresClass 4 Lasers can ignite some substances

Irradiance greater than 10 W/cm2

Improperly ventilated beam enclosuresFlammable dyes 39

Non-Beam Hazards

Non-Beam Hazards

Fire HazardExplosions and Radiation

• Separate flammables• Construct with fire-

resistant materials• Keep fire extinguishers

nearby• Shield against radiation

(X-ray, Plasma, RF, and Microwaves)

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Non-Beam Hazards

Laser

ProtectiveHousing

Interlock Warning Light

Beam Block41

Engineering Controls

Eliminate ExposureUse physical structures as your first line of

defense

1. Protective housing2. Interlocks3. Aperture beam blocks4. Warning lights

Engineering Controls

Interlockto laser or shutter

Laser curtainat entry

Storageof eyewear protection

Controlled Accessto laser area

Warning signon door

Warning light

Fire Extinguisher

Warning labelson equipment

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Engineering ControlsEliminate ExposureUse physical structures as your first line of

defenseBeam attenuators decrease

the power per unit area of laser beams through absorption and scattering of the beam.

Use beam attenuators on high powered lasers:Class 3BClass 4

Administrative Controls

Rules and PoliciesFollow all rules and

guidelines1. Laser Safety Training-

Every 3 Years (You and everyone you are working with)

2. Follow posted rules and regulations

3. Post warning signs if hazards are present

4. Restrict access5. Register all laser

machines

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DANGER sign

High powered lasers (Class 3B, 3R, 4)Eye damage (permanent) or burn possible.

NOTICE sign

Alignment, installation, or repair in progress.Injury possible.

CAUTION sign

Strong lasers (Class 2, 2M)Eye damage possible.

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Administrative Controls

Follow procedures Isolate laser operations

Never leave unattended

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Administrative Controls

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Alignment ProceduresSafety Precautions-Most laser-related injuries occur

during alignment!When performing alignment on “beam out of the

box” devices, follow these rules:1. Remove metal jewelry, watches, and badges

before beginning any activities 2. Prepare all equipment and materials prior to

beginning 3. Use non-reflective tools 4. Arrange for someone else to be present 5. Remove unnecessary equipment, tools, and

combustible material to minimize the possibility of stray reflections and non-beam accidents.

6. Make sure to keep objects out of the path of the beam.

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Exclude unnecessary personnel from the laser area during alignment.

2. Where possible, use low-power visible lasers for path simulation of high power visible or invisible lasers.

3. Wear protective eyewear during alignment. Use special alignment eyewear when circumstances permit their use.

4. When aligning invisible beams, use beam display devices such as image converter viewers or phosphor cards to locate beams.

5. Perform alignment tasks using high-power lasers at the lowest possible power level.

6. Use a shutter or beam block to block high-power beams at their source except when actually needed during the alignment process.

7. Use a laser rated beam block to terminate high-power beams downstream of the optics being aligned.

8. Use beam blocks and/or laser protective barriers in conditions where alignment beams could stray into areas with uninvolved personnel.

9. Place beam blocks behind optics to terminate beams that might miss mirrors during alignment.

10. Locate and block all stray reflections before proceeding to the next optical component or section.

11. Be sure all beams and reflections are properly terminated before high-power operation.

12. Post appropriate area warning signs during alignment procedures where lasers are normally class 1.

13. Alignments should be done only by those who have received laser safety training.

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Other Safety PrecautionsWHENEVER Working with laser machines:

1. Wear PPE at all times during operation, and when a Class 1 laser enclosure is open.

2. Reduce the beam power using filters, beam splitters and dumps, or the lowest possible power supply. Avoid using high-power during alignment.

3. Label the areas where the beam leaves the horizontal plane. 4. Work around (or avoid) beam paths that are at sitting or

standing eye level. Direct beam away from eye level, and keep body parts out of the beam path.

5. Simulate the beam path using lower power visible lasers6. Terminate any stray or unused beams. Use beam shutters to

block high power beams any time they aren't needed. Terminate the beam at the end of its useful path. Eliminate all beams and reflections prior to high power operation.

7. View invisible beams with IR/UV cards or sensor cards; taking care to avoid specular reflections off of some of these materials.

8. Do not look directly at the beam! You can prevent from intentional intra-beam viewing with the eye by using cameras or fluorescent devices to view the beam

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Never intentionally look directly into a laser. Do not stare at the light from any laser. Allow yourself to blink if the light is too bright.

Do not view a Class 3a (or any higher power) laser with optical instruments. Never direct the beam toward other people. Operate lasers only in the area designed for their use and be certain that the beam is terminated at the

end of its use path. Never allow a laser beam to escape its designated area of use. Position the laser so that it is well above or below eye level. Always block the beam with a diffuse reflecting beam block. Remove all unnecessary reflective objects from the area near the beam’s path. This may include items

of jewelry and tools. Do not enter a designated Class 3b or Class 4 laser area (posted with a DANGER sign) without approval

from a qualified laser operator. Eye protection is required in these areas. Always wear laser safety eyewear if a class 4 invisible beam is exposed.

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Personal Protective Equipment

PPEThe strategy of last

resort 1. Ensure proper fit2. Select proper PPE for

the job3. Make sure PPE is

properly maintained and not damaged

4. Use consistently

Use laser eye protection.Do not rely onyour blink reflexfor protection.

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Personal Protective Equipment Your body has a natural aversion response when it comes in contact with a laser beam. Your head will tend to turn, and your eyes naturally blink. This response occurs every ¼ of a second, and is used to calculate laser hazards. However, because it may not always occur in all incidents, you should not rely on this response as a substitute for laser eye protection.

Use laser eye protection.Do not rely onyour blink reflexfor protection.

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Safety eyewear that protects against chemicals, dust, impact, or heat do not have the proper lens filters to protect against laser beams and are not for use with Lasers

Personal Protective Equipment

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Personal Protective EquipmentSafety EyewearUse safety eyewear that protects

against optical radiation through:

• Neutral density absorbs and reflects

• Bandpasstransmits weaker light

• Cut-offblocks light at one end

Ultraviolet Visible Infrared

Argon(488 nm and 514 nm)

KTP(532 nm) Ruby

(694 nm) Nd:YAG(1060 nm)

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Personal Protective EquipmentSafety EyewearSelect eyewear based on

wavelength.

The wavelengths that the eyewear can be used to protect against is labeled on the eyewear, generally on the lens itself.

012345678

100 % 10 1 0.10 0.01 0.001 0.0001 0.00001 0.000001

Optical Density (OD)

Light transmission

100%transmission

10%transmission

1%transmission

OD = 0

OD = 1

OD = 2

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Safety Eyewear

012345678

100 % 10 1 0.10 0.01 0.001 0.0001 0.00001 0.000001

Optical Density (OD)

Light transmission

100%transmission

10%transmission

1%transmission

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Safety Eyewear

012345678

100 % 10 1 0.10 0.01 0.001 0.0001 0.00001 0.000001

Optical Density (OD)

Light transmission

010

1001,000

10,000100,000

1,000,00010,000,000

100,000,000

Outputpower

mW

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Safety Eyewear

012345678

100 % 10 1 0.10 0.01 0.001 0.0001 0.00001 0.000001

Optical Density (OD)

Light transmission

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Safety Eyewear

Select laser safety eyewearbased on the optical densityand wavelength of your laser.

In addition to…

FitField of Vision PrescriptionSensor Card UseDegradation

Too much space Proper fit

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For more information

ehs.ucsc.edu

(831) 459-2553

ehs@ucsc.edurad@ucsc.educsherma1@ucsc.edu