INTRODUCTION TO LASERS

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INTRODUCTION TO LASERS

• TECHNOLOGY EDUCATION
• SCARSDALE MIDDLE SCHOOL

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Many of the pictures for this LASER
presentation came from www.howstuffworks.com.
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LASER

• Originally LASER was an acronym for Light
  Amplification by the Stimulated Emission of
  Radiation.
• Now laser is a word used to identify this type of
  equipment or the light it produces.

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The Atom
Different electron orbits represent different
energy levels.
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The Electron
Applying energy to an electron causes it to
jump to a higher orbit.
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The Photon
When the electron drops back to its original
orbit it releases a particle called a photon.
Light is made up of photons.
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Wavelength of Light
Light moves in waves that are similar to ripples
in water.
Light is an example of electromagnetic radiation
It doesnt require a medium to pass through
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Wavelength of Light
1 CYCLE
Wavelength (?) The distance the wave travels
in one cycle. Frequency (f) The number
of times a cycle repeats in one second
(Hertz, formerley cycles/second). ?
c f
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Wavelength of Light
HERTZ ? ENERGY 400
nanometers 700 nanometers
HIGHER FREQUENCY
LESS ENERGY
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1 NANOMETER IS ONE BILLIONTH OF A METER
A human hair is about 80,000 nanometers in
diameter.
Thats about 115 times the wavelength (?) of red
light.
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Light BulbLight is not focusedLight is made
up of many colors (wavelengths)Light is not
coherent
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White Light

• Light From A
• Light Bulb
• All colors
• (wavelengths).
• More longer
• wavelengths.
• Light is not
• coherent.
• Light is not
• focused.

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Laser Light Light is very focusedLight is
made up of one color (wavelength)Light is
coherent
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Laser Light

• Light From A
• Laser
• One color
• (wavelength).
• Light is coherent.
• Light is focused.

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Theodore MaimanFirst Ruby Laser1960
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How a Laser Works
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Ruby Laser
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Types of LasersBased on the Material Used in the
Laser
Classes of LasersBased on the Biological Damage
the LaserCan Cause
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Typical Lasers and Their Emission Wavelengths

• Laser Type Wavelength (nm)
• Argon fluoride (UV) 193
• Krypton fluoride (UV) 248
• Nitrogen (UV) 337
• Argon (blue) 488
• Argon (green) 514
• Helium neon (green) 543
• Helium neon (red) 633
• Rhodamine 6G dye (tunable) 570 - 650
• Ruby (CrAlO3) (red) 694
• NdYag (NIR) 1064
• Carbon dioxide (FIR) 10600

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Optical Damage Threshold TestNASA Research Center
The Optical Damage Threshold test station at NASA
Langley Research Center has three lasers a
high-energy pulsed NDYag laser, a Tisapphire
laser and an alignment HeNe laser.
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Classes of LasersBased on the Biological Damage
the Laser Can Cause
Class I Lasers that dont produce any harmful
radiation. Class II Lasers that are harmful
if viewed for long periods of time. (The
assumption is that people wouldnt let this
happen.) Class III Lasers that are dangerous for
short exposure. (Many laser pointers are class
III lasers!) Class IV Lasers that can blind or
burn after a very brief exposure. These can
only be used under very controlled conditions.
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LASER WEAPONS
Do you expect me to talk Goldfinger? No Mr.
Bond, I expect you to die.
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Laser Gun Sights
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Multiple Integrated Laser Engagement
SystemMILES (2000) Laser Tag for Soldiers
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Laser Targeting SystemAircraft Mounted
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Laser Guided Bomb(Smart Bomb)
Control surfaces
Guidance system
Optical sensor
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Laser Targeting

• Laser targeting
• system paints
• target.

2. Laser guided weapon tracks laser spot
on target.
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Laser Targeting SystemGround Based
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Laser Targeting CountermeasuresAN/VVR-1 Laser
Warning Receiver System
System detects the targeting laser.
Countermeasures include smoke, brighter
laser beam, maneuvering, etc.
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Laser Guided Missile
Hellfire laser guided missiles mounted on a US
Army Apache helicopter gunship.
Newer variation (Hellfire II) replaces laser
guidance with radar guidance to penetrate smoke
and cloud cover.
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ABLAirborne LaserAntimissile WeaponUnited
States Air Force
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ABLNose Turret
CO2 Targeting Laser
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LASERS IN MANUFACTURING
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Punch Press
Typical Stamped Parts

• Punch Press Problems
• Dangerous to operate.
• Required long runs
• to be profitable.

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Laser Cutter
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Computer Controlof Laser Cutter Equipment

• No human contact
• with the part during operation.
• Computer program
• can be loaded
• quickly. Shorter
• runs are now
• profitable.

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Laser Welding
Welded Parts
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Laser Welding
Welded car door panel made from three types of
steel.
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Laser Stereolithography(SLA)
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Part Produced bySLA
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LASERS IN MEDICINE
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Laser Eye SurgeryLAser in SItu Keratomileusis
(Lasik)
1. Tiny flap of outer cornea folded back.
2. Laser removes tissue from remaining
cornea to change its shape.
3. Flap of outer cornea then reattached.
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Laser Tattoo Removal(Doesnt always work!)
The laser beam breaks up the pigments in the
tattoo into small particles. Then the bodys
immune system attacks and destroys them.
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Laser Dentistry
Water jet
Laser

• Major advantage is no drilling sound.
• Cant be used on existing metal fillings.

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LASER TESTING AND MEASURING
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Laser Bar Code Scanning
Universal Product Code (UPC) Label
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Barcode on a UPS Label
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Barcode Scanner
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Railroad Car SortingUsing Barcode Scanning
Labels were often too dirty for the scanners to
read.
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Laser Surface Roughness Tester
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Laser Level
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Laser Speed MeasurementNew York State Police
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Telescope Calibration Lick Observatory
The adaptive optics system at the Shane 3 meter
telescope utilizes a 20-watt sodium laser to put
a false star in the sky. The system uses the star
to compensate for atmospheric disturbances,
creating sharper, clearer images of the objects
observed.
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LASER COMMUNICATION
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Laser Printer
Corona Wire
Discharge Lamp
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Laser Disk
Land
Pit
Beam reflects logical 1.
Beam doesnt reflect logical 0.
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Laser Disk Drive
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MODULATIONSuperimposing a weak signalon a
strong one
MODULATED LASER BEAM Changes in the beam
represent information in the audio signal.
Audio
Laser Carrier
DEMODULATOR Removes audio signal from the
modulated laser beam.
MODULATOR Combines audio signal and laser beam.
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FIBER OPTICSTransparent Pipe for Light to
Travel Through

• Advantages
• Very high capacity.
• Cant be tapped into.
• Not affected by electromagnetic (EM)
  interference.
• Allows light to travel around corners.

• Disadvantages
• Expensive.
• Can be difficult to install.

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Fiber OpticsCenter fiber optic cable has greater
capacitythan any of these bundles of cable.