SOME BASICS

OF

LASERS

L
A
S
E
R

Light
Amplification by
Stimulated
Emission of
Radiation

WHAT IS A LASER ?

A laser is a device that

transforms light of
various frequencies into
a chromatic radiation in
the visible, infrared, and
ultraviolet regions with
all the waves in phase
capable of mobilizing

 Light beam is composed of packets of energy

known as PHOTONS
Ground State Atoms are normal position
Atoms are excited by an energy source and
move to a higher energy
As it reverts back to its ground state, energy
is emitted Spontaneous Emission
Results without external interference and
forms waves that are in phase

HOW COHERENT AND

INCOHERENT LIGHT WAVES
DIFFERS ?

AMPLIFICATION
Is a part of a process that occurs
inside the laser
An optical cavity is at the center of
the laser device & the core is
comprised of chemical elements,
molecules or compounds Active
Medium
Lasers are generically named for the
material of the active medium
Gas, Crystals or Semi-Conductors

AMPLIFICATION
Gas Co2 & Argon
Solid state semi conductors :
With metals like Gallium, Aluminum, Indium,
Arsenic
With solid rods of garnet crystal growth with
various combinations of Yytrium, Aluminum,
Scandium, Gallium and then doped with
elements of Chromium, Neodynium or Erbium.

AMPLIFICATION
The crystal or gas is excited to emit
photons of a characteristic wavelength
These ware amplified and filtered to
make a coherent beam
The effect of this energy depends on
whether or not the WL of the energy is
absorbed by the surface or not

STIMULATED EMISSION
Quantum theory of Max Planck &
Neils Bohr
Smallest unit of energy
It can be absorbed by electrons,
cause brief excitation and then the
quatum is released Process called
as Spontaneous Emission

RADIATIO
N

Refers to light waves produced by

the laser as electromagnetic energy
EM Spectrum entire range
Wavelengths

.Within the visible or invisible infrared

non-ionizing EM range & emit thermal
radiation

.The dividing line between ionizing

Laser consists of a lasing

medium contained with an
optical cavity, with an
external energy source to
maintain a population
inversion so that stimulated
emission of a specific
wavelength can occur,
producing monochromatic,
collimated and coherent
beam of light

 Active medium Gas, liquid or solid

Contained in glass or ceramic tubes
Energy Electric current
Mirrors are added to each end to
increase the back and forth
movement of photons
Thus increasing the stimulation of
emission of radiation

LASER DELIVERY
SYSTEMS
Two delivery systems that are
employed
1. Hollow Waveguide or Tube

2. Glass fiber optic cable

1. FLEXIBLE HOLLOW WAVEGUIDE (TUBE)

Has an interior finish mirror

Laser energy is reflected along this
tube and exits through a hand piece
Strikes the tissue in a non-contact
manner
An accessory tip of sapphire or

2. G LA SS FIB ER O P TIC C A B LE
More flexible than waveguide
Less weight and less resistance in movement
Smaller diameter (200-600 m)
Glass component is encased in a resilient sheath
Fragile & cant be bent in sharp angles
Used in contact and non-contact mode

Glass Fiber
(Flexible)

Waveguide
(Tube)

Argon

Er

Diode

Cr:YSGG

Nd:YAG

Er:YAG
CO2

Fiber Optic

WAVEGUIDE
TUBE

WHAT DOES THE

OPERATOR CONTROL?
Level of
applied
power
(Power
Density)

Total
energy to
be
delivered
(Energy
density)

Rate &
Duration
of
exposure
(Pulse
Repetitio
n)

Mode of
energy
delivery

Light Amplification by

Stimulated
Emission of Radiation
Spontaneous emission

Stimulated emission

ENERGY LEVEL
DIAGRAM

The possible energies which

electrons in the atom can have is
depicted in an energy level diagram.
E
4
E
3
E2

E
1

LASER

The operation of
the Laser
E4

E3
E2

E1

(Pumping the Laser)

The operation of
the Laser
E4
E3

E2

E1

absorption

The operation of
the Laser
E4
E3
E2

E1

Spontaneous emission

The operation of
the Laser
Spontaneous
emission

1. Incoherent light

2. Accidental direction

The operation of
the Laser
E4
E3
E2

E1

The operation of
the Laser
E4
E3
E2

E1

Stimulated emission

The operation of
the Laser
Light: Coherent, polarized
The stimulating and
emitted. photons have
the same:

Frequency,
Phase,

TWO LEVEL SYSTEM

E2

h
h=E2-E1

E2

E1
absorption

Spontaneous
emission

E1
Stimulated
emission

TYPES OF LASER
1. Based on the mode of operation
(i) Pulsed Laser systems
(ii) High power Q-switched systems
(iii) Continuous wave Laser systems
2.Based on the mechanism in which Population
Inversion is achieved
(i) Three level lasers
(ii) Four level lasers
3.Based on state of active medium used
(i) Gas Laser
(ii) Solid state Laser
(iii) Semiconductor Laser
(iv) Tunable dye Laser

THE ELECTROMAGNETIC SPECTRUM

LASER FUNDAMENTALS

The light emitted from a laser is monochromatic, that is, it

is of one color/wavelength. In contrast, ordinary white light
is a combination of many colors (or wavelengths) of light.
Lasers emit light that is highly directional, that is, laser
light is emitted as a relatively narrow beam in a specific
direction. Ordinary light, such as from a light bulb, is
emitted in many directions away from the source.
The light from a laser is said to be coherent, which means
that the wavelengths of the laser light are in phase in
space and time. Ordinary light can be a mixture of many
wavelengths.
These three properties of laser light are what can
make it more hazardous than ordinary light. Laser light
can deposit a lot of energy within a small area.

INCANDESCENT

VS LASER LIGHT

1. Many wavelengths

1. Monochromatic

2. Multidirectional

2. Directional

3. Incoherent

3. Coherent

Common Components of all Lasers

1. Active Medium
The active medium may be solid crystals such as ruby or
Nd:YAG, liquid dyes, gases like CO2 or Helium/Neon, or
semiconductors such as GaAs. Active mediums contain atoms
whose electrons may be excited to a metastable energy level by
an energy source.
2. Excitation Mechanism
Excitation mechanisms pump energy into the active medium by
one or more of three basic methods; optical, electrical or
chemical.
3. High Reflectance Mirror
A mirror which reflects essentially 100% of the laser light.
4. Partially Transmissive Mirror
A mirror which reflects less than 100% of the laser light and
transmits the remainder.

LASER
COMPONENTS

Gas lasers consist of a gas filled tube placed in the

laser cavity. A voltage (the external pump source) is
applied to the tube to excite the atoms in the gas to
a population inversion. The light emitted from this
type of laser is normally continuous wave (CW).

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

LASING ACTION
1.
2.
3.
4.
5.
6.
7.
8.

Energy is applied to a medium raising electrons to an unstable

energy level.
These atoms spontaneously decay to a relatively long-lived, lower
energy, metastable state.
A population inversion is achieved when the majority of atoms have
reached this metastable state.
Lasing action occurs when an electron spontaneously returns to its
ground state and produces a photon.
If the energy from this photon is of the precise wavelength, it will
stimulate the production of another photon of the same wavelength
and resulting in a cascading effect.
The highly reflective mirror and partially reflective mirror continue
the reaction by directing photons back through the medium along
the long axis of the laser.
The partially reflective mirror allows the transmission of a small
amount of coherent radiation that we observe as the beam.
Laser radiation will continue as long as energy is applied to the
lasing medium.

Lasing Action
Diagram
Excited State
Spontaneous
Energy Emission

Energy
Introduction

Metastable State

Stimulated Emission
of Radiation

Ground State

WAVELENGTHS OF MOST COMMON LASERS

Laser Type
Argon fluoride (Excimer-UV)
Krypton chloride (Excimer-UV)
Krypton fluoride (Excimer-UV)
Xenon chloride (Excimer-UV)
Xenon fluoride (Excimer-UV)
Helium cadmium (UV)
Nitrogen (UV)
Helium cadmium (violet)
Krypton (blue)
Argon (blue)
Copper vapor (green)
Argon (green)
Krypton (green)
Frequency doubled
Nd YAG (green)
Helium neon (green)
Krypton (yellow)
Copper vapor (yellow)

Key:

Wavelength (m)
0.193
0.222
0.248
0.308
0.351
0.325
0.337
0.441
0.476
0.488
0.510
0.514
0.528
0.532
0.543
0.568
0.570

Helium neon (yellow)

Helium neon (orange)
Gold vapor (red)
Helium neon (red)
Krypton (red)
Rohodamine 6G dye (tunable)
Ruby (CrAlO3) (red)
Gallium arsenide (diode-NIR)
Nd:YAG (NIR)
Helium neon (NIR)
Erbium (NIR)
Helium neon (NIR)
Hydrogen fluoride (NIR)
Carbon dioxide (FIR)
Carbon dioxide (FIR)

UV = ultraviolet (0.200-0.400 m)
VIS = visible (0.400-0.700 m)
NIR = near infrared (0.700-1.400 m)

0.594
0.610
0.627
0.633
0.647
0.570-0.650
0.694
0.840
1.064
1.15
1.504
3.39
2.70
9.6
10.6

Laser Output
Pulsed Output (P)

Energy (Watts)

Energy (Joules)

Continuous Output (CW)

Time

Time

watt (W) - Unit of power or radiant flux (1 watt = 1 joule per second).
Joule (J) - A unit of energy
Energy (Q) The capacity for doing work. Energy content is commonly used to characterize the output
from pulsed lasers and is generally expressed in Joules (J).
Irradiance (E) - Power per unit area, expressed in watts per square centimeter.

WAVE NATURE OF LIGHT

Wavelength

Blue: = 400
nm

Light is an electromagnetic
wave.
Different wavelengths in the
visible spectrum are seen by
the eye as different colors.

Red: = 700
nm

ELECTROMAGNETIC SPECTRUM
Blue

Green

Yellow

Red

Visible
Gamma
Ray

X-ray

Short
Wavelength

Ultraviole
t

Infrared

Radio
Microwave
s

Radi
o

Long
Wavelength

Lasers operate in the ultraviolet, visible, and

infrared.

STIMULATED EMISSION
Incident Photon

Incident Photon
Excited Atom

Stimulated Photon
same wavelength
same direction
in phase

CHARACTERISTICS OF LASER LIGHT

MONOCHROMATIC
DIRECTIONAL
COHERENT

The combination of these three

properties makes laser light focus
100 times better than ordinary light

SIMPLE EXAMPLE
OF LASER

: HELIUM-NEON GAS LASER

APPLICATIO
NS
OF
LASERS

APPLICATION OF LASER
Many scientific, military,

medical and
commerciallaser
applicationshave been
developed since the invention
of thelaserin 1958. The
coherency, high
monochromaticity, and ability

SCIENTIFIC
In science, lasers are used in

many ways, including:

A wide variety ofinterferometric
techniques
Raman spectroscopy
Laser induced breakdown spectr
oscopy
Atmosphericremote sensing
Investigatingnonlinear optics

 Holographictechniques

employing lasers also contribute

to a number of measurement
techniques.
Laser based
LIght Detection And Ranging (LI
DAR)
technology has application in
geology,seismology, remote
sensing and
atmospheric physics.

 In astronomy, lasers have been used to

create artificiallaser guide stars, used

as reference objects foradaptive optics
telescopes.
Lasers may also be indirectly used in
spectroscopy as a micro-sampling
system, a technique termed Laser
ablation(LA), which is typically applied
toICP-MSapparatus resulting in the
powerful LA-ICP-MS.
The principles of laser spectroscopy are
discussed by Demtrderand the use of
tunable lasers in spectroscopy are

DOPPLER
EFFECT
DOPPLER SHIFT

RED SHIFT

BLUE SHIFT

COSMOLOGICAL GRAVITATIONAL

Definition:- There is an apparent change

in frequency of the sound waves emitted
from the source, when there is a relative
motion between the source and the
observer. This effect is called Doppler
effect and the shift in frequency is called

LASER COOLING
The use of Lasers to

achieve extremely
low temperatures
has advanced to the
temperatures of 10e9 K.
These laser cooling
can be used for
transmitting power
without any loss
from power station
to sub station

COMMUNICATION
AT PRESENT
The speed of the
communication is
high,
But still the
communication with
the outer world is still
lagging.
IN FUTURE
Using LASER the
communication to
other galaxy is

COMPUTING
SPEEDS

At present the computing speed ranges from

256 kilobits per

second to 1 gigabit per second, which is slow
for the present
world.
The ability to achieve a speed of 25 gigabits
per second can be done with the use of laser
chips.

Lasers are already used to transmit

high volumes of computer data over

longer distances for example,
between offices, cities and across
oceans using fibre-optic cables. In
computer chips, data moves at great

MILITARY
DEFENCE

1. Find Target

An infrared camera on the laser

continuously scans a 6 to 10-mile
radius around the airport for
suspicious heat emissions. When it
finds a plume, it relays the coordinates
to an identification and tracking
system, which is also on the unit.

2. Confirm Threat

The onboard computer checks the

objects heat signature against a data
bank, confirms that its a missile (and
not a bird or a plane), and activates
the laser.

3. Prepare to Fire

Reactive gases in the lasers fuel tanks

are funneled through a vacuum tube
to heat up atoms and send them
cascading through resonator mirrors.
This produces a tightly focused, highenergy beam.

4. Destroy Missile

The laser-beam cannon emits a burst

of intense light aimed at the missiles

MILITARY
Militaryuses of lasers

include applications such

astarget designation
and ranging, defensive
countermeasures,
communications and
directed energy weapons

METEOROIDS
ATTACKS

The concept which was

used for military defence

can be used to destroy
the meteoroids coming
towards earth.
These incoming
meteoroids can be
shattered into pieces,
thus saving our earth
from any major
destruction.
A group of strong laser
beams are focused
together to the target and
the target is shattered off.

LASER IN
We are proposing our own idea for the
use of AUTOMOBILES
laser light in automobiles. All

automobiles have ball bearings in there

wheels, these bearings wear off while
use and this may cause accidents. To
prevent these accidents we use a laser
beam to detect the position of the shaft
in the wheels, on one end there will be a
laser and the other end a sensor is kept,
when the ball bearing malfunctions the
shaft position is moved from the original
position, now the sensor is activated.
This sensed signal is sent to the user.

MATERIAL PROCESSING
Laser cutting,

laser welding, laser

brazing, laser bending,
laser engraving or
marking, laser cleaning,
weapons etc. When the
material is exposed to
laser it produces intense

LASER COOLING
A technique that has recent success

islaser cooling. This involves

atom trapping, a method where a
number of atoms are confined in a
specially shaped arrangement ofelectric
andmagnetic fields. Shining particular
wavelengths of laser light at the ions or
atoms slows them down,
thuscoolingthem. As this process is
continued, they all are slowed and have
the same energy level, forming an

MEDICAL

Cosmetic surgery (removing tattoos,

scars, stretch marks, sunspots, wrinkles,

birthmarks, and hairs): see
laser hair removal. Laser types used in
dermatologyincluderuby(694nm),
alexandrite(755nm), pulsed diode array
(810nm),Nd:YAG (1064nm),Ho:YAG
(2090nm), andEr:YAG (2940nm).
Eye surgeryandrefractive surgery

 Soft tissue surgery:CO2,Er:YAG laser

Laser scalpel(General surgery,

gynecological, urology, laparoscopic)

Photobiomodulation(i.e. laser therapy)
"No-Touch" removal of tumors, especially

of the brain and spinal cord.

Indentistryforcariesremoval,endodontic/

periodontic

procedures,tooth whitening,

CURIOSITY USING ITS

LASER DEVICE IN ITS
MISSION

OTHER APPLICATIONS
Cuttingandpeeningof metals and other

material,welding, marking, etc.

Laser drilling
Guidance systems(e.g.,ring laser gyroscopes)
Rangefinder/surveying,
LIDAR/ pollution monitoring,
Laser cladding, a surface engineering process

applied to mechanical components for

reconditioning, repair work orhardfacing
Laser accelerometers

INDUSTRIAL AND
Levelling of ceramic tiles floor
COMMERCIAL
with a laser device

LASERS USED FOR VISUAL EFFECTS DURING

A MUSICAL PERFORMANCE. (ALASER LIGHT SHOW )

 Laser line levelsare used in surveying and construction. Lasers

are also used forguidance for aircraft.

Extensively in both consumer and industrial imaging equipment.
Inlaser printers: gas and diode lasers play a key role in

manufacturing high resolution printing plates and in image

scanning equipment.
Diode lasersare used as a lightswitch in industry, with a laser

beam and a receiver which will switch on or off when the beam is
interrupted, and because a laser can keep the light intensity over
larger distances than a normal light, and is more precise than a
normal light it can be used for product detection in automated
production.
Laser alignment
Additive manufacturing
Inconsumer electronics,telecommunications, and

data communications, lasers are used as the transmitters in

optical communicationsoveroptical fiberandfree space.
To store and retrieve data inoptical discs
Laser lighting displays(pictured) accompany many music

concerts.

Digital minilabs
Barcode readers
Laser engravingof printing plate
Laser bondingof additive marking
materials for decoration and identification,

LASER POINTERS:

Holography
Bubblegrams
Photolithography
Optical communications(over
optical fiberor infree space)
Optical tweezers
Writingsubtitlesontomotion picture
films.[18]
Space elevator, a possible solution
transfer energy to theclimbersbylaser
ormicrowavepower beaming
3D laser scannersfor accurate 3D

IS
LASER
DANGER ?

LASER BEAM INJURIES

High power lasers can

cause skin burns.
Lasers can cause severe
eye injuries
resulting in permanent
vision loss.

aser-Professionals.com

SKIN BURN FROM CO2 LASER

EXPOSURE

Accidental exposure to partial reflection of 200

W CO2 laser beam
from metal surface during cutting

LASER CLASSIFICATION
SYSTEM
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

Safe with no viewing aids

Visible wavelengths only

1mW

Class 2
Visible wavelengths only

0.5W
220W to 0.4W

Class 1M
Class 1

Safe with (0.25 s.) aversion

response including viewing aids
Safe with no viewing aids
No precautions
required

OLD LASER CLASSIFICATION

SYSTEM

Approx. Power Limits for CW

Visible Wavelengths Only

Class 4
0.5 W

Class 3B

5 mW

Class 3A

1 mW

Class 2
Visible wavelengths only

Unsafe for eyes

Unsafe for skin

Unsafe for eyes

Generally safe for skin

Safe with (0.25 s.) aversion

response no viewing aids

Safe with (0.25 s.) aversion

response including viewing aids

220W to 0.4W

Class 1

No precautions
required

LASER SAFETY
PRECAUTIONS
BY CLASSIFICATION
Class 1 Lasers :

- Safe

Class 1M Lasers:

- No viewing aids

Class 2 Lasers :
response

- Safe with aversion

(No staring)

Class 2M Lasers:
response

- Safe with aversion

(No staring); No viewing

aids
Class 3R Lasers :
aids,
(also old Class 3A lasers)

- No Staring, No viewing
Unsafe outside visible

LASER SAFETY
PRECAUTIONS
BY CLASSIFICATION,
CONTINUE.
Class 3B Lasers :

- Unsafe for eyes, generally

safe for skin

Class 4 Lasers :
for

- Unsafe for eyes, unsafe

skin

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

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

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

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.

THANK
YOU

REFERENCES