This document discusses types of lasers and their applications. It begins with an introduction to lasers and their basic requirements. It then describes different laser types including solid-state, semiconductor, dye, gas and excimer lasers. The document outlines various scientific applications such as laser spectroscopy, metrology and cooling. It also discusses commercial uses in cutting, welding, printing and displays. Medical laser applications include cosmetic surgery, dentistry and imaging. Finally, military laser applications are described for countermeasures, guidance and targeting.

1. TYPES OF LASER AND APPLICATIONS
Bahir Dar University, College of Science, Department of Physics
By:Getnet Tegenie
Advisor: Dr. GETASEW ADMASU(PhD)
January, 2021
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2. Overview
1 Introduction To Laser
2 Fabry Perot
3 Laser Modes
4 Types of Laser
5 Applications of Laser
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3. Introduction To Laser
The acronym word laser means light amplification by stimulated
emission of radiation.
An optical source that emits photons in a coherent beam.
A device which produces any particles or electromagnetic radiations in
a coherent state is called Laser, e.g., Atom Laser.
In most cases laser refers to a source of coherent photons i.e., light or
other electromagnetic radiations.
It is not limited to photons in the visible spectrum.
Lasers are generally applied in commercial, industrial, bio-medical,
scientific and military applications.
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4. Properties of Laser
I Monochromatic: with one color/wavelength
I Directionality: estimulated light propagate in particular direction
I Coherency: estimulated Laser lights are in phase and same direction
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5. Basic requirements of any Laser
An active medium with a suitable set of energy levels to support laser
action.
Active medium can be
1 Solid state Lasers
2 Gas lasers
3 Semiconductor Lasers
A source of pumping energy in order to establish a population
inversion.
An optical cavity or resonator to introduce optical feedback and so
maintain the gain of the system overcoming all losses.
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6. Fabry Perot
A set of two or more mirrors arranged to cause light to propagate in a
closed path is called an optical resonator
The simplest resonator consists of two mirrors, and a ring resonator
consists of at least three mirrors.
Any given mirror may be characterized by its amplitude reflection
coefficient r and its transmission coefficient t.
Typically we are interested in the intensity reflectivity R and
transmission T.
Consider the simplest two-mirror resonator having a monochromatic
laser beam incident on the input mirror.
It describes the intensity of light transmitted through the output
mirror, and the intensity of light reflected from the resonator.
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7. Laser Modes
Characteristics that affect laser performance are
the power output and mode of emission:- continuous wave, pulsed,
Qswitched or Mode locked lasers.
CW laser- emits a continuous beam of light as long as medium is
excited.
Pulsed laser- emit light only in pulses- from femtoseconds to second
Q-switched laser-pulses from micro to nanosecond are produced
Mode-Locked laser pulses from pico (10-12s) - to femto seconds (
10-15s) are produced
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8. cont..
I Lasers operated in Continuous Wave (CW) or Pulsed modes.
I CW lasers-energy is continuously pumped - producing a continuous
laser output.
I Pulsed lasers - the pump energy is applied in pulsesusually with a
flash lamp
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9. Laser: Q-switching
Q-switching is a way of obtaining short - from a few nano -seconds to
few tens of nano -seconds powerful - from a few megawatts to few
tens of megawatts- pulses of laser.
Q - quality factor of laser resonator.
High Q Low losses
Low Q - High losses
The term Q-switching refers to an abrupt switching of the cavity Q
from low value to a high value.
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10. Methods of Q-switching:
There are many ways to Q-switch a laser:-
Active Q-switching
1 Mechanical devices- shutters, chopper wheel or spinning mirror.
2 Electro-optic device: Pockel cells and kerr cells.
3 Acousto-optic device
Passive Q-switching
1 Q-switch is a saturable absorber
.
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11. cont..
The active medium is excited without feedback -by blocking the reflection
from one of the end mirrors of the cavity
The end mirror is then suddenly allowed to reflect
Suddenly applied feedback causes a rapid population inversion of the
lasing levels
Results in a very high peak power output pulse of short duration
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12. Techniques for Q switching
Using a mechanically driven device:-
1 A rotating prism or mirror
2 Rotate one of the mirrors about an axis perpendicular to the laser
3 Rotating speed cannot be made very large
4 Q switching does not take place instantaneously
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13. Types of Laser
Lasers are usually classified in terms of their active (lasing) medium.
Major types of Lasers are:-
1 Solid-state lasers
2 Semiconductor Lasers
3 Dye Lasers
4 Gas Lasers
5 Excimer Lasers
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14. Types of Laser
Solid-state lasers
1 have lasing material distributed in a solid material
2 such as ruby or neodymium: yttriumaluminum garnet ”YAG”).
3 Flash lamps are the most common power source.
4 The Nd:YAG laser emits infrared light at 1.064 micrometers.
Semiconductor lasers
1 sometimes called diode lasers- are pn junctions.
2 Current is the pump source.
3 Applications: laser printers or CD players.
Gas lasers are pumped by current.
1 Helium-Neon lases in the visible and IR.
2 Argon lases in the visible and UV.
3 CO2 lasers emit light in the far-infrared (10.6 micro m)
4 are used for cutting hard materials.
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15. Applications of Laser
Laser considered to be ”a solution in search of a problem in 1958.
Now Laser has many applications:
1 Scientific Applications
2 Commercial Applications
3 Medical Applications
4 Military Applications
The properties like Coherence, mono-monochromaticity, and ability to
reach extremely high powers, allow for these specialized applications.
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16. Scientific Applications
Laser Spectroscopy:
atmospheric physics - pollution monitoring-cancer detection
Optical metrology:
optical distance, optical temperature measurements etc...
Optical frequency metrology:
for precise position measurements
Laser induced breakdown spectroscopy:
Solid materials can be analyzed
Laser cooling:
makes it possible to bring clouds of atoms or ions to extremely low
temperatures
Optical tweezers:
used for trapping and manipulating small particles- such as bacteria or
parts of living cells.
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17. Scientific Applications
Laser microscopes:
provide images of, e.g., biological samples with very high resolution -
often in three dimensions
Optical fiber communication:
extensively used for long-distance optical data transmission-relies on
laser light in optical glass fibers.
Free-space optical communications:
for inter-satellite communications- is based on higher-power lasers-
generating collimated laser beams which propagate over large
distances with small beam divergence.
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18. Commercial Applications
I Cutting, welding, marking,
I Rangefinder / surveying,
I LIDAR / pollution monitoring,
I CD/DVD player,
I Laser printing,
I Laser engraving of printing plates,
I Laser pointers, holography, laser light displays
I Optical communications.
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19. Medical Applications
Cosmetic surgery
Dentistry
Dermatology
Eye surgery
Cardiology
Neurology
Urology
Optical Imaging
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20. Medical Applications
Cosmetic surgery: removing tattoos, scars, stretch marks, wrinkles,
birthmarks, and hairs.
Dentistry: caries removal, tooth whitening, and oral surgery.
Dermatology: Treatment of acne and skin cancer by PDT
Eye surgery: Cataract and Glaucoma surgery
Cardiology: Angioplasty, vessel recanalization
Neurology: To cut, ,vaporize and coagulate tissue with out
mechanical contacts
Urology: lithotripsy (removal of kidney stones)
Laser scalpel: gynecology, urology, laparoscopy
Optical Imaging: field of online monitoring and diagnostics
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21. Military Applications
1 Defensive counter measures
IR counter measure systems use lasers to confuse the seeker heads on
infrared homing missiles.
2 Disorientation
Some weapons simply use a laser to disorient a person
3 Laser guidance
is a technique of guiding a missile or other projectile or vehicle to a
target by means of a laser beam.
4 Target designator
Another military use of lasers is as a laser target signator by shone
infrared onto the target.
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