Centre for Lasers & Applications - Deakin University

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Nov 15, 2013 (4 years and 1 month ago)

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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


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 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

High Voltage

40 kV

Water Cooling

Insulation

Materials

Oil Cooling

(Hot Oil)

Laser Beam

200W

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 CW

Visible Wavelengths Only

Class 4

Unsafe for eyes

Unsafe for skin

0.5W

Class 3B

Unsafe for eyes

Generally safe for skin

5mW

Class 3R

Safe with (0.25 s.) aversion
response no viewing aids

0.5W

Class 2M

Visible wavelengths only

Safe with no viewing aids

1mW

Class 2

Visible wavelengths only

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

0.5W

Class 1M

Safe with no viewing aids

220
μ
W to 0.4
μ
W

Class 1

No precautions

required

Laser Classification System

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

Unsafe for eyes

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

220
μ
W to 0.4
μ
W

Class 1

No precautions


required

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

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


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 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 controls

Hierarchy of controls


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 3B & 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 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, C
lass 1 &
2
Laser Pointers


Laser,
C
hemical and
E
lectrical 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 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