OHS026
Safe work procedure
1. Completed by:
Peter Reece
Staff/Student number:
2173999
The Writing Safe Work Procedures Guideline (OHS027) should be consulted to assist in the completion of this form
Faculty/Division: SCIENCE
Document number
SWP45-01-VisLaser.docx
School/Unit: PHYSICS / OPTOELECTRONICS
Initial Issue date
1 Dec 2011
Current version
1.0
Current Version
Issue date: 1 Dec 2011
Next review date
1 Dec 2012
2.Safe work procedure title and basic description of activity
Title: Alignment procedure for UV lasers (CLASS 3R, 3B & 4)
Lasers can be hazardous for a number of reasons, the most important of which is the danger associated with radiation
damaging the eye or the skin. Other non-beam related hazards include electrical, chemical and environmental. The
degree of possible damage to the eye and skin is a function of the wavelength of emission, the power in the beam,
energy density and duration of the laser radiation.
UV lasers have additional hazards compared with conventional visible lasers which require the need for
additional safety considerations:
1. UV lasers are invisible to the eye and as such the eye has no natural aversion response viewing
potentially hazardous levels of laser radiation.
2. Strong UV light sources produce are known to long term skin damage (including skin cancer) when
exposed to
3. Strong pulsed UV light sources, such as the Nitrogen Laser produce ozone and which can be toxic in
when built up in confined spaces.
Description of activity:General procedures associated with incorporating a UV laser with safety classification (CLASS 3R, 3B & 4) into an
experimental optical arrangement. These procedures cover a number of situations routinely performed within a
research lab conducting optical and spectroscopic measurements. Specific tasks include:
1. CASE 1: Establishing a beam line where no existing optical components are present
2. CASE 2: Redirection of an established beam path or gross alignment where the beam may deviate from any
optical component within the optical train.
3. CASE 3: Fine alignment where the beam will not deviate from any one component, but where the beam spot at
the end of the beam path will be modified.
4. CASE 4: Optical alignment where the beam is not directly manipulated, but the scattered light is modified.
The safe work practices described here are designed with Class 4 lasers, which afford the greatest risk in terms of
laser related eye damage, burns and skin damage and fire hazard, however they may also be considered as general
good practices to adopt for handling all types of laser classes.
Lasers that are relevant to this SWP:
Nitrogen Laser, Coherent Cube 375.
WARNING: Always complete a risk assessment and seek approval from the academic-in-charge before starting a new
optical experiment involving UV lasers.
3.List Hazards and risk controls as per risk assessment
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Associated risk
assessment
number and
location:
Hazards
Controls
Electrical Shock: Ionized gas lasers require
potentially lethal levels of voltage and current to
generate and maintain the plasma in the gain
medium. These are provided by the threephase power supplied to the laboratory.
The manufacturer has provided a series of
interlocks to limit user-access to the
dangerous electrical hazards during normal
operation. These interlocks should never be
defeated by the user unless under the direct
supervision of a qualified service engineer.
Flooding: An associated electrical shock
hazard comes from the use of recirculating
water that is used to cool the power supply and
laser head. The flow required to cool the laser
head is approximately 10 litres a minute and as
there is no floor drainage, in the event of a
major rupture, the lab can quickly become
flooded. There is also the possibility that there
will be a leak within the laser and/or power
supply leading to a potential malfunction of the
laser. Both types of leaks have the potential to
expose the operator and others in the lab to
electrical hazards.
All power in the Optoelectronics Lab has
residual current protection to safeguard
against flooding related electrical shock.
To avoid excessive pressure build-up inside the
laser head during the start-up procedure the
cooling water outlet tap is always opened first
when before opening the inlet. When shutting
down the laser the inlet tap is closed first.
The inlet and outlet connections to the laser
should be checked for leakage after the
cooling water is turned on. If leakage occurs
the laser should be switched off immediately
and the source of the leak should be identified
and fixed.
To avoid abrupt temperature changes inside
the laser head the shutdown procedure
includes allowing the cooling water should be
run for several minutes after the laser is
switched off.
Eye damage: Permanent eye damage may
result in viewing the laser beam along the
beam path with the naked eye or ocular viewing
instrument. The specific type of damage
caused to the eye is related to the wavelength,
intensity and pulse duration. For lasers in the
visible spectrum (400nm to 780nm) the most
common damage is photochemical and
thermal retinal image injury, resulting in
temporary or permanent impairment of
peripheral or total vision.
Unaccompanied lab entry is restricted (by a
locked door) to anyone un-inducted into the
laboratory.
In the case of Class 4 lasers there is an
additional ocular hazard related viewing of
diffuse reflections when operating under high
powers. In instances where the amount of
exposure due to scattering exceeds the
Maximum Permissible Exposure (MPE) for this
particular laser and direct viewing can cause
eye damage.
Strong diffuse reflection should be terminated
at the optical bench with anodized black metal
baffles and curtains.
Burns: Direct exposure of the skin to a Class 4
laser beam can lead to skin damage ranging
from mild erythema to sever blistering. Longterm effects include, increased pigmentation,
ulceration and scarring.
Where possible, restrict access to beam paths
where the laser beam operating at high powers.
Strict procedural guidelines outlined in
section 5 of this document must be adhered at
all times when working with lasers.
Laser safety goggles are provided as Personal
protective equipment to cover each laser type
housed in the Optoelectronics Laboratory.
Strict procedural guidelines outlined in
section 5 of this document must be adhered at
all times when working with lasers. (3. Never
place your hand or other part of your body or
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clothing into the direct beam path when laser is
running at high powers.)
Fire Hazard: Class 4 lasers operating at high
power have the potential to ignite flammable
materials including, paper, fabric, etc.
Where possible, restrict access to beam paths
where the laser beam operating at high powers.
Strict procedural guidelines outlined in
section 5 of this document must be adhered at
all times when working with lasers. (4. Never
place flammable objects in the path of a Class4 laser operating at high powers.)
Restrict the use of flammable solvents and
oxidizing agents in the vicinity of a Class 4
laser operating under high powers.
4.List resources required including personal protective clothing, chemicals and equipment needed
Laser safety goggles: Personal protective equipment designed to protect the operator from direct exposure to a specific
range of laser wavelengths. Each goggle has an optical density rating (i.e. level of attenuation of light) for each spectral
band that they provide protection.
Anodized black metal baffles: Metal shields designed to block diffuse scattered light and weak specular reflections and
limit laser light to the confines of the optical bench. May also be used to shield stray scattered light from sensitive optical
instrumentation.
Beam stop – a beam stop is designed to terminate a beam line or strong reflection without producing significant
scattering. Beam stops have a large thermal mass to accommodate the energy absorbed from the . The surface is also
designed to the heat
Viewing card – typically a white card that is used to visualize the beam path under low excitation intensities.
Mechanical marker – typically a white card or variable aperture mounted on an optical base. This is used to define the
beam height and aid with alignment of the laser to the desired beam path.
5.List step by step instructions or order for undertaking the task
General safe-handling protocols:The following practices apply to all visible lasers (UV and IR lasers have additional constraints):
1. Lasers cannot be handled without proper training from the Area Supervisor (Peter Reece).
2. Never view the laser beam directly along the beam path with your naked eye or any kind of optical viewing
apparatus.
3. Never place your hand or other part of your body or clothing into the direct beam path when laser is running at
high powers.
4. Never redirect a laser beam with unmounted optics.
5. **Never place flammable objects in the path of a Class 4 laser operating at high powers.
6. Never place strong diffuse scatterers (e.g. a white card) in front of a class 4 laser operating at high powers.
7. Where possible, maintain the laser beam path to a plane parallel to the optical bench and well below the viewing
height of the operator.
8. Fix all optical component firmly to the optical bench once alignment is complete.
9. Periscope arrangements are only appropriate to change the height of the beam with respect to optical bench or
when passing the beam through a microscope column. Laser beams should never be directed out of the plane
towards the ceiling in an uncontrolled manner.
10. Always keep your head above the height of the beam path at all times.
11. Never allow the laser beam or any associated specular reflections to stray from the optical bench in an
uncontrolled manner; this represents a hazard to your work colleagues.
12. Always terminate the laser beam or strong collimated stray reflections using a beam-dump, beam-stop or metal
baffle. Black curtains do not block stray reflections.
13. Never perform any gross alignment of a laser beam under high power; attenuate the beam to a level that is
equivalent to a class II laser for the wavelength and temporal mode of operation for the laser.
14. Always visually check the intended beam path for obstructions and termination conditions before setting the laser
to high power operation.
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15. For lasers with cooling water and three-phase power, always turn off the cooling water after the cool-down
procedure has been completed.
16. Laser safety goggles are only appropriate for procedures where minor adjustments to the beam path are required
and shouldn’t be used for gross alignment.
17. Complete Risk Assessments for all new optical experimental set-ups.
Task-specific protocols:1. PROCEDURE FOR ESTABLISHING A NEW BEAM LINE (CASE 1)
1. Ensuring that the laser aperture is closed or blocked with a beam-stop, start the laser as per the model specific
instructions – given below.
2. Plan the beam path on paper and identify all of the optical components that are necessary to complete the optical
train.
3. Clear the space on the optical bench where the beam path is desired.
4. Working from the laser aperture, place each mounted optical component of the train in place and direct the beam
towards the next planned component - always place a baffle after the final mounted optical component.
5. During the gross alignment procedures goggles should be worn and the beam power should be attenuated to a
safe level either using the power controls or a suitable external attenuator.
6. Other group members working in the lab should be made aware when gross alignment procedures are in being
conducted.
3. PROCEDURE FOR OPTICAL GROSS ALIGNMENT (CASE 2)
Gross alignment procedures, where the laser beam deviates significantly from an existing optical beam path or walks off
any optical component within the optical train, should always be performed with the laser power at a minimum operating
power.
2. PROCEDURE FOR OPTICAL FINE ALIGNMENT (CASE 3)
1. The laser start up procedure is unique to the particular laser system in use. The start-up procedure for each of
the lasers used in the Optoelectronics Lab is detailed at the end of this section.
2. The laser beam (or associated specular reflections) should never deviate from the optical bench where the
experiment is being performed.
3. Use a beam-stop to terminate strong optical reflections and anodized metal baffles for all other stray reflections.
4. PROCEDURE FOR INSTRUMENT OPTIMISATION (CASE 4)
Once the laser beam is set with appropriate termination conditions, associated optical apparatus for measuring sample
properties may be aligned. An example such a procedure includes alignment of collection optics for measuring
photoluminescence from a semiconductor sample. This typically is achieved using the diffuse scattering of the laser from
the sample surface or the sample holder.
LASER START UP PROCEDURES
Coherent INNOVA 70 argon ion lasers
1. Slowly open the outlet tap of the recirculating cooling water mounted on the wall adjacent to the Power supply.
The direction of flow is indicated on the pipes.
2. Slowly open the inlet tap of the recirculating cooling water and check there is no leaking at the input and output
connections.
3. Switch the aperture on the front of the laser to closed.
4. Switch the key on the power supply followed by the switch on the control panel – if the cooling water is flowing
correctly the flow interlock indicator will blink once.
5. Press the start button on the control panel and wait for the laser tube to fully ionize (approximately 30 seconds).
6. During the start up procedure the laser cycles through to maximum optical power and therefore it is important to
ensure that the beam is terminated using a beam stop or the aperture during this time.
7. With the aperture closed turn up the current to about 90% of its maximum operating current (~ 35A). The argon
ion lasers take about half an hour to an hour to warm to stable operation and it is important to run it at close to full
capacity during this period.
8. Once the warm up process is completed adjust the current to the desired output power.
Coherent INNOVA 90 argon ion laser
1. Slowly open the outlet tap of the recirculating cooling water mounted on the wall adjacent to the Power supply.
The direction of flow is indicated on the pipes.
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2. Slowly open the inlet tap of the recirculating cooling water and check there is no leaking at the input and output
connections.
3. Switch the aperture on the front of the laser to closed.
4. Switch the key on the power supply followed by the switch on the control panel – if the cooling water is flowing
correctly the flow interlock indicator will blink once.
5. Press the start button on the control panel and wait for the laser tube to fully ionize (approximately 30 seconds).
6. During the start up procedure the laser cycles through to maximum optical power and therefore it is important to
ensure that the beam is terminated using a beam stop or the aperture during this time.
7. With the aperture closed turn up the current to 41.5A. The argon ion lasers take about an hour to an hour to warm
to stable operation and it is important to run it at close to full capacity during this period.
Quantronix - Frequency Doubled Q-switched YAG Laser
1. Place a beam-stop in front of the laser to block the exit aperture.
2. Slowly open the outlet tap of the recirculating cooling water mounted on the wall adjacent to the power supply.
The direction of flow is indicated on the pipes.
3. Slowly open the inlet tap of the recirculating cooling water and check there is no leaking at the input and output
connections on the power supply or laser head.
4. Turn the key on the power control unit and press and hold the interlock button until the pump is running
continuously.
5. Set the triggering conditions – if no external trigger is used set the triggering mode to “int”
6. Adjust the current control to a minimum (counter-clockwise to the stop)
7. Switch the power button and wait for a few seconds until the flash lamp has ignited.
8. Increase the current until the laser light is observed to exit the aperture.
Coherent Cube Diode Lasers
1. Switch the aperture on the front of the laser head to closed.
2. Turn on the power to the laser at the mains power supply
3. Switch the secondary power switch to provide power to the control unit and laser hear.
4. Turn the key on the control unit and wait 5 seconds.
5. The power on the laser may be adjusted via a software interface if the laser is connected to the computer by the
serial or USB port.
6.List emergency shutdown procedures
Argon ion lasers (Innova 70 and Innova 90 series)
7.List Emergency procedures for how to deal with fires, spills or exposure to hazardous substances
In the event of an electrical fire
8.List Clean up and waste disposal requirements
N/A
9.List legislation used in the development of this SWP
Laser Safety Standard: AS/NZS 2211.1:2004
10.List competency required – qualifications, certificates, licensing, training - e.g. course or instruction:
UNSW Lab Induction
UNSW Optoelectronics Laser Safety Induction
11.Supervisory approval, And review
Supervisor:
Peter Reece
Responsibility for SWP review: Peter Reece
Signature:
Date of review: 1 June 2012
12.SWP Sign off sheet
SWP name and version: Alignment procedure for visible lasers (CLASS 3R, 3B & 4)
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In signing this section the assessor/ authorisor agrees that the following persons are competent in following this
SWP
Name
Signature
Date
Competent
Name of Assessor/Authoriser
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Assessor/Authoriser
signature