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Laser
Lesson objectives
What is laser?
 Applications of laser around us
 Laser radiation hazards
 Laser classification
 Laser safety
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What is a laser?
A laser is a device that emits light
(electromagnetic radiation) through a
process called simulated emission.
 The term laser is an acronym for light
amplification by simulated emission of
radiation.
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(from http://en.wikipedia.org/wiki/laser )
Overivew of laser
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In 1917 Albert Einstein, Zur Quantentheorie der
Strahlung (On the Quantum Theory of Radiation)
The first working laser was demonstrated on 16
May 1960 by Theodore Maiman at Hughes
Research Laboratories.
Applications: optical storage devices such as
compact disc and DVD players (largest), fiberoptic communication (second largest)
Video (Record 5 events/applications of lasers)
Properties of laser
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Spatially coherent
 The electric fields at
different positions
oscillate in a totally
correlated way
 Strong directionality of
laser beams
Monochromatic (not for
all lasers)
 Narrow wavelength
spectrum
Design of laser
Gain medium
 High reflector
 Energy supply
 Laser output
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Applications of laser
Medicine: bloodless surgery, laser healing
 Industry: Cutting, welding, material heat
treatment
 Defense: marking targets, missile defense
 Research: spectroscopy, laser scanning
 Commercial: laser printer, CDs, barcode
scanners
 Aesthetics: laser light shows
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Laser radiation hazards
Coherent light, low divergence angle
concentrate on a small spot on the
retina
 Laser radiation predominantly causes
injury via thermal effects.
 A transient increase of only 10 °C can
destroy retinal photoreceptors.
 Some lasers are so powerful that even the
diffuse reflection from a surface can be
hazardous to the eye.
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Laser classification
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Class I: inherently safe (light
enclosed), e.g. CD players
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Class II: safe during normal
use (damage prevented by
blink reflex of the eye) e.g.
laser pointers
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Class IIIa/3R: up to 5mW,
small risk of eye damage
Laser classification
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Class III/3B: up to 500mW,
immediate severe eye
damage upon exposure, e.g.
those in CD burners.
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Class IV: burn skin, even
scattered light can cause eye
damage. Many industrial and
scientific lasers are in this
class.
Laser safety
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Laser safety is the avoidance of laser accidents,
especially those involving eye injuries.
Safety measures
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Everyone who uses a laser should be aware of the
risks.
Optical experiments should be carried out on an
optical table with all laser beams travelling in the
horizontal plane only, and all beams should be
stopped at the edges of the table. Users should never
put their eyes at the level of the horizontal plane
where the beams are in case a reflected beam leaves
the table.
Laser safety
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Safety measures (cont’d)
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Watches and other jewelry that might enter the optical
plane should not be allowed in the laboratory. All nonoptical objects that are close to the optical plane
should have a matte finish.
Adequate eye protection should always be required
for everyone in the room if there is a significant risk
for eye injury
High-intensity beams that can cause fire or skin
damage (mainly from class 4 and ultraviolet lasers)
and that are not frequently modified should be guided
through tubes
Alignment of beams and optical components should
be performed at a reduced beam power whenever
possible
Laser safety
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Protective eyewear
Spectacles or goggles with appropriately
filtering optics
 Eyewear must be selected for the specific
type of laser, to block or attenuate in the
appropriate wavelength range
 The protective specifications (wavelengths
and optical densities) are usually printed on
the goggles
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Laser safety
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Laser safety officer
In many jurisdictions, organizations that
operate lasers are required to appoint a laser
safety officer (LSO).
 The LSO is responsible for ensuring that
safety regulations are followed by all other
workers in the organization.
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Group Activity
4 people in a group (Individual
responsibility)
 Poster Design for introduction of lasers
 15 minutes
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