Optical Instrumentation u1

7/31/2019 Optical Instrumentation u1

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OPTICAL

INSTRUMENTATION

ANUJ BHARDWAJ (UNIT-1) 1


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INTRODUCTION

Optical instrumentation has become even more firmly established as a

subject in its own right & an increasing number of courses in physics &

electronic engineering include aspects of optoelectronics.

An optical instrument either processes light waves to enhance an image forviewing, or analyzes light waves (or photons) to determine one of a

number of characteristic properties

http://en.wikipedia.org/wiki/Light_wavehttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Light_wavehttp://en.wikipedia.org/wiki/Light_wavehttp://en.wikipedia.org/wiki/Light_wave


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SYLLABUS

Unit:1 ) light sourcing, transmitting and receiving

Concept of light , Classification of different phenomenon based on theories of

light, Basic light sources and its characterization , Polarisation ,Coherent and

Incoherent sources , Grating theory, Application of diffraction grating, Electro-optic

effect, Acousto-optic effect, Magneto- optic effect Unit:2 ) Opto- Electronic devices and Optical components

Photo diode, PIN, Photo- Conductors, solar cells, Photo transistors, Materials

used to fabricate LEDs and Lasers Design of LED for optical communication,

Response times of LEDs , LED drive circuitry, Lasers classification: Ruby lasers,

Neodymium Lasers, He-Ne lasers, Dye lasers, Semiconductors lasers, Lasersapplications



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Unit-3)InterferometryInterference effect, Radio-metery, Types of interference phenomenon and its

application,Michelsons Interferometer and its application , Fabry-Perotinterferometer , Refractometer,Rayleighs interferometers, Spectrographs andMonochromators,Spectrophotometers,Calorimeters,Medical Optical Instruments

unit-4) HolographyPrinciple of Holography, On-axis and Off axis Holography , Application ofHolography , Optical data storage

optical fiber sensorsActive and passive optical fiber sensor, Intensity modulated displacement type

sensors, Multimode active optical fiber sensor (Microbend sensor ) Single Modefiber sensor-Phase Modulates and polarization sensors



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Unit-1( Light sourcing, Transmitting and

Receiving )Concept of light , Classification of different phenomenon based ontheories of light, Basic light sources and its characterization ,

Polarisation ,Coherent and Incoherent sources , Grating theory,

Application of diffraction grating, Electro-optic effect, Acousto-optic

effect, Magneto- optic effect



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UNIT-1 ( Light sourcing, Transmitting and

Receiving )

Concept of light : Light is electromagnetic radiation of wavelength that is visible

to the human eye ( about 400-700 nm ).Light is composed of elementary

particles called photons.

Three properties of light :

a)Intensity b) frequency c) polarization

Light can exhibit properties of both waves and particles.



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Nature of light

What am I?

Waves? Particles?ANUJ BHARDWAJ (UNIT-1) 9


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The Nature of Light- described by different

theories

Quantum TheoryLight consists of small

particles (photons)

Wave TheoryLight travels as a transverse

electromagnetic wave

Ray TheoryLight travels along a straight

line and obeys laws ofgeometrical optics.

Ray theory is valid when the objects aremuch larger than the wavelength

(multimode fibers)



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Classification of different phenomenon based on theories

of light

Image formation - ray theory

Wavelength color,

polarization anddiffraction -

wave theory (electricityand magneticsm)

Interaction of light withatoms - quantum theory of

photons

Constant speed of light

no matter how fast the

source or observer is

moving - special theory of relativity



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Different theories of light

given by different scientist



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A long time ago

Aristotle (384 - 322 B.C.), an ancient Greek thinker, thought that

we saw the world by sending something out of our eye and that

reflected from the object.

In Platos time (427 347 B.C.), the reflection of light from

smooth surfaces was known. He was also a Greek.

The ancient Greeks (about 200 A.D.) also first observed therefraction of light which occurs at the boundary of two

transparent media of different refractive indices.



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Isaac Newton1643 - 1727

Christian Huygens1629 - 1695

In the17th century, two scientists had different views

about the nature of light

Light is

particles

No! Light is

waves



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Laws of Reflection

According to the Laws of Reflection,

angle of incidence = angle of reflection (i= r)

Incident light ray Reflected light ray

Normal

i r



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Laws of Refraction

Willebrord Snell discovered in 1621 that when a wave travelsfrom a medium of refractive index, n1 , to one of differentrefractive index, n2 ,

n1sin(1) = n2sin(2)

This relationship is calledSnells Law

Incident light rayNormal

Refracted light ray

1

2

n1

n2

Interface

Light bends towards the normal when ittravels from an optically less dense medium

to an optically more dense medium.ANUJ BHARDWAJ (UNIT-1) 17


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Newton proposed his particle theory of light (orcorpuscular theory of light) to explain the characteristics of

light.(source: Opticks, published by Isaac Newton in 1704)

I think light is a stream of tiny

particles, called Corpuscles



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Why does light have different colours?

The particles of different colours have different

properties, such as mass, size and speed.

Why can light travel through a vacuum?

Light, being particles, can naturally pass through vacuum.(At Newtons time, no known wave could travel through a

vacuum.)

Particle Theory



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Why does light travel in straight lines?

A ball thrown into space follows a curved path because of

gravity.

Yet if the ball is thrown with greater and greater speed, its

path curves less and less.

Thus, billions of tiny light particles of extremely low mass

travelling at enormous speeds will have paths which are

essentially straight lines.



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How does the particle theory explain the Laws of

Reflection?

The rebounding of a steel ball froma smooth plate is similar to the

reflection of light from the

surface of a mirror.

Steel Ball Rebound

Light Reflection

Mirror

Many light

particles in a light rayANUJ BHARDWAJ (UNIT-1) 21


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A cannon ball hits the surface of water, it is acted upon by arefracting force which is perpendicular to the water surface. Ittherefore slows down and bends away from the normal. Light doesthe opposite. Newton explained this observation by assuming thatlight travels faster in water, so it bends towards the normal.

(What was the problem in this explanation?)

The problem:

Does light really travel

faster in water?

In fact nobody could measure

the speed of light at the time of

Newton and Huygens

How does Newton's particle theory explain the Laws of Refraction?

Cannon ball Light

Water

Air



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Lets see how Huygens used his wave theory toexplain the characteristics of light

I think light is emitted as a series of

waves in a medium he called aether

(source: Treatise on light, published by Huygens in 1690)

(aether commonly also called ether)



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A wave starts at P and a wavefront W

moves outwards in all directions.

After a time, t, it has a radius r, so that

r= ct if c is the speed of the wave.

Each point on the wavefront starts

a secondary wavelet. These secondarywavelets interfere to form a new wavefront

W at time t.

How do waves propagate?

P



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How can wave theory explain the Laws of Refraction?

Opticallydensermedium

n1sin1 = n2sin2

can be proved by geometry.

Refer to the appendix of the

worksheet or your textbookfor the proof.

Click here for animation

Wavefront W1 reaches the boundary between media 1 & 2, point A of

wavefront W1 starts to spread out. When the incoming wavefrontreaches B, the secondary wave from A has travelled a shorter

distance to reach D. It starts a new wavefront W2. As a result the

wave path bends towards the normal.

Air A

C

B

D

W1

W2

1

2

http://d/Eudora/Attach/propagation.htmlhttp://d/Eudora/Attach/propagation.htmlhttp://d/Eudora/Attach/propagation.htmlhttp://d/Eudora/Attach/propagation.html


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If light behaves as waves, diffraction and interference should be seen. Theseare two important features of waves. This was known in the 17th century.

(You can see this easily with water waves in a ripple tank)

The wave theory of light predicts interference anddiffraction. However, Huygens could not provide any

strong evidence to show that diffraction and interference

of light occurred.

Diffraction and interferenceof water waves



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Newton was the winner.. (at that time!)

Newtons particle theory of light dominated optics during

the 18th century.

Most scientists believed Newtons particle theory of light

because it had greater explanatory power.

Lets consider the reasons



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Sounds can easily be heard around an obstacle butlight cannot be seen around an obstacle. Light, unlikesound, does not demonstrates the property ofdiffraction and it is unlikely to be a type of wave.

(1)Waves do not travel only in straight lines,

so light cannot be waves.



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(3) Particle theory of light can explain why there are

different colours of light.

Huygens could not explain why light has different colours

at all. He did not know that different colours of light havedifferent wavelengths.

Though Newtons explanation was not correct (particles

of different colours of light have different mass and size),his particles theory could explain this phenomenonlogically in the 17th century.

?ANUJ BHARDWAJ (UNIT-1) 32


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(4) Reputation of Newton

People tend to accept authority when there is notenough evidence to make judgement. Newtonsparticle theory could only explain refraction by

incorrectly assuming that light travels faster in a densermedium. No one could prove he was wrong at thattime.

The uncertainty about the speed of light in water remained

unresolved for over one hundred years after Newton's death.



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However, the wave theory of light wasre-examined 100 years after Newtons particle theory of light had been

accepted

Thomas Young

1773 - 1829

Light is not

particles!



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Thomas Young successfully

demonstrated theinterference of light (which

Huygens failed to show),

by his famous double-slit

experiments.

Since then the wave

theory of light has been

firmly established.



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The wave theory of light was widely accepted until1905

Albert Einstein

1879 - 1955

Wave theory oflight? No way!



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The photoelectric effect is observed when light strikes a metal,

and emits electrons.

Einstein used the idea of photons (light consists of tiny particles)

to explain results which demonstrate the photoelectric effect.



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Light

What evidence did Einstein find in his

photoelectric effect experiments that

helps to support the particle theory of

light?

In the setup investigating the photoelectric effect (as shown

below), the intensity of the light, its frequency, the voltageand the size of the current generated are measured.

e-



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fC

For certain metals, dim blue light can generate a currentwhile intense red light causes no current at all.

Below a certain cut off frequency

of light ( ), no voltage is

measurable.

Why does the wave theory of light

not explain the result?

Results from photoelectric effect experiments

Voltage

Frequencyof light

n0

fC fANUJ BHARDWAJ (UNIT-1) 39


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Albert Einstein provided a piece of convincing evidence for the particle

nature of light

Has the story ended yet?

Is light particles or waves?

Louis de Broglie

1892 - 1987

Light is not particles, not

waves, but BOTH!



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Louis de Broglie in 1924 proposed that particles also have

wave-like properties, this was confirmed experimentallythree years later.

Most scientists did not understand de Broglies Ph.D.dissertation at that time. One scientist passed it on to

Einstein for his interpretation. Einstein replied that deBroglie did not just deserve a doctorate but a Nobel Prize!

De Broglie was awarded the

Nobel Prize in 1929.



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Aristotle ( Light was emitted from our eyes )

Christian Huygens ( Wave theory of light )

Isaac Newton ( Particle theory of light )

Thomas Young ( Wave theory of light )

Albert Einstein ( Particle theory of light )

de Broglie ( Wave-particle duality of all matter)

Summary



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Summary: What can we learn from the historical development about the

understanding the nature of light?

Evidence(e.g. Youngs double slit experiment, photoelectricexperimental resultsetc) can establish or refute a theory.

Gathering scientific knowledge (the nature of light) is hardwork, building upon the hard work of other scientists in thepast or present. (collaboration across time)

Scientific knowledge is ever changing, sometimes even

revolutionary (Einstein discovered the particle nature of light,de Broglie discovered the

wave-particle duality of all matter)



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Some properties of light...

light travels more slowly in an optically dense

medium than it does in a less dense medium

A measure of this effect is the refractive index (indexof refraction)

Gives us refraction and reflection

materialinlightofSpeed

invacuumlightofSpeed=h h > 1



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Reflected Rays

h1

h2

a

a= acceptance angle

c= critical angle

Incident Ray Reflected

Ray

c

Partial Reflection

Exit Ray


T l i l fl i i f b di f h


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Total internal reflection is an extreme case of a ray bending awayfrom the

normal as it goes from a higherto alowerindex of refraction medium (from a

slowerto afastermedium)

Glass orwater

(slow)

Normal

Air (fast medium)

Just below thecritical angle for totalinternal reflection there is a reflectedand a transmitted (refracted) ray

Glass or

water

(slow)

Normal

Just abovethe critical angle for total

internal reflection there is a reflected raybut no transmitted (refracted) ray

Critical

angle

For the glass-air interface



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Total internal reflection



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Basic light sources and its characterisation:There are many sources of light. The most common light sources are

black body radiation

Incandescent light bulbs

Flames

Certain other mechanisms can also produce light: scintillation

Electroluminescence

Sonoluminescence

Cherenkov radiation

For characterisation of these sources , we have to discuss their properties,that how they emit light, what is the spectrum region..etc etc.



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Polarisation :Thisphenomenon tells the

transverse nature of light.

We can understand this by

doing simple experiment.



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Experiment:

light from a source S fall on a tourmaline crystal A cut parallel to itscrystallographic axis shown dotted in fig on next slide.

Second crystal B is placed in the path of beam.

Now if B is rotated, the intensity of the emergent light decreases and no light

comes out of the crystal B when B is right angle to A .

Thus it can be easily inferred that light is transverse motion.



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experiment



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Plane polarised light may bedefined as the light in which

the light vector vibrates

along a fixed straight line in

a plane perpendicular tothe direction of

propagation.



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Pictorial representation of light vibrations



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Brewsters law

According to this law,when light is incident at the

polarizing angle the

reflected and refracted rays

are perpendicular to eachother.



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Coherence

Purpose Neglect temporal dependence Coherence light -> stable interference Degree of coherence interference fringes visibility

What light is coherent Monochromatic temporal coherence Coherence length

Spherical waves spatial coherence Coherence area

Formal description Binary relation Cross correlation between two signals



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I t f i i h t f h ith d


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Interfering many waves: in phase, out of phase, or with random

phase

Waves adding exactly

in phase(coherent

constructive addition)

Waves adding withrandom phase,partially canceling

(incoherentaddition)

If we plot the

complex

amplitudes:

Re

Im

Waves adding exactly

out of phase, adding tozero (coherentdestructive addition)



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h f l h b lb h


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Light from a light bulb is incoherent

Itotal = I1 + I2+ + In

When many light waves add withrandom phases, we say the light is

incoherent, and the light wave totalirradiance is just the sum of the

individual irradiances.

Other characteristics of incoherent light:

1. Its relatively weak.

2. Its omni-directional.

3. Its irradiance is proportional to the number of emitters.ANUJ BHARDWAJ (UNIT-1) 60

C h t I h t Li ht


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Coherent vs. Incoherent Light

Itotal = I1 + I2+ + InEtotal = E1 + E2

+ + En

Coherent light:1. Its strong.

2. Its uni-directional.

3. Total irradiance N2 or0.

4. Total irradiance is the mag-squareof the sum of individual fields.

Incoherent light:1. Its relatively weak.

2. Its omni-directional.

3. Total irradiance N.

4. Total irradiance is the sum ofindividual irradiances.

Laser



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Diffraction

What exactly is diffraction

Everything not being reflection or refraction

Interference of many sources

Scalar Diffraction

Easier in certain environment

Huygens-Fresnel principle More precise formulations

Kirchhoff

Rayleigh-Sommerfeld

t

t

t-Dt

t-Dt

t+Dt

t+Dt

Direction of

propagation

Direction of

propagation

) ) sdsoiyxu srsrik

S

cos

~

,~

|)(|

|))(|exp(

=1



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Diffraction is a phenomenon when a wave

that passes through an aperture or around an

obstacle forms a pattern on a screen.

What causes diffraction is interference of an

infinite number of waves that are emitted by

the points of the aperture



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There are two different limiting types ofdiffraction observations

- Fresnel diffraction patterns

- Fraunhofer diffraction patterns



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For Fraunhofer diffraction pattern there is alarge distance between aperture and the

screen.

For Fresnel diffraction the distance between

the aperture and the screen is generally

small.


l f l diff i


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Example of Fresnel diffraction



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Airy disk: This is a Fraunhofer diffraction.



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Grating theory: diffraction

grating is an arrangementequivalent to a large number of

parallel slits of equal widths and

separated from each other byequal opaque spaces.


A single beam of light will scatter off of the grating and emerge as many beams with indices m

0 1 2 3 The outgoing beam with m 0 is called the "zeroth order" beam and it goes


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= 0,1,2,3,,,,. The outgoing beam with m = 0 is called the zeroth order beam and it goes

straight through. The beam with m=1 is called the "first-order" beam and the beam with

m=2 is called the "second order" beam.

All of these higher orders beams have the same color (wavelength) as the incident beam.

Each order m refers to a pair of diffracted beams that emerge from the grating at

angles from the initial beam's direction.

The directions of the beams diffracted from the initial beam of wavelength is given by the

relation,



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A diffraction grating is the tool of choicefor separating the colors in incident light.

The condition for maximum intensity is

the same as that for a double slit.

However, angular separation of the

maxima is generally much greater because

the slit spacing is so small for a diffraction

grating.

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/slits.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/slits.html


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Diff ti


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Diffraction

ordersBecause the diffraction angle depends

on , different wavelengths are

separated in the nonzero orders.

No

wavelength

dependence

occurs in

zero order.

The longer the wavelength, the larger its deflection in each

nonzero order.

Diffraction angle, m()

Zeroth order

First order

Minus

first order

Incidence

angle, i


Diffraction grating dispersion


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Because diffraction gratings are used to separate colors, its helpful to

know the variation of the diffracted angle vs. wavelength.

Differentiating the grating equation,

with respect to wavelength:

Diffraction-grating dispersion

cos( ) mm

da md

=

sin( ) sin( )m ia m - =

cos( )

m

m

d m

d a

=

Rearranging:

[i is constant]

Thus, to separate different colors maximally, make a small, work in high

order (make m large), and use a diffraction angle near 90 degrees.

Gratings typically have an

order of magnitude moredispersion than prisms.


Any surface or medium with


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periodically varying or n is a

diffraction grating.

Transmission gratings can be amplitude () or phase (n) gratings.

Gratings can work in reflection (r) or transmission (t).


Real diffraction


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gratings

Diffracted white light

White light diffracted by a real grating.

m = 0 m =1m = 2

m = -1

The dots on a CD areequally spaced (although

some are missing, of

course), so it acts like a

diffraction grating.

Diffraction

gratings



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The tracks of a compact

disc act as a diffraction

grating, producing a separation ofthe colors of white light. The nominal

track separation on a CD is 1.6micrometers, corresponding to about

625 tracks per millimeter. This is in

the range of ordinary laboratory

diffraction gratings. For red light of

wavelength 600 nm, this would give

a first order diffraction maximum atabout 22 .


Application of diffraction grating
http://hyperphysics.phy-astr.gsu.edu/hbase/audio/cdplay.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/audio/cdplay.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/audio/cdplay.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/audio/cdplay.html


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Application of diffraction grating

GRATINGS FOR INSTRUMENTAL ANALYSISAtomic and molecular spectroscopy

Fluorescence spectroscopy

Colorimetry

Raman spectroscopy

GRATINGS IN LASER SYSTEMS

Laser tuning

Pulse stretching and compression

GRATINGS IN ASTRONOMICAL APPLICATIONS

Ground-based astronomy

Space-borne astronomy

GRATINGS IN SYNCHROTRON RADIATION BEAMLINES

SPECIAL USES FOR GRATINGS

Gratings as filters Gratings in fiber-optic telecommunications

Gratings as beam splitters

Gratings as optical couplers

.Gratings in metrological applications

http://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asphttp://gratings.newport.com/information/handbook/chapter13.asp


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Colorimetryis the measurementand specification of color, used inanalytical chemistry, color matching,color reproduction and appearancestudies. Because color as perceivedcannot be associated with a singlewavelength it is a more complicated

function of how the three differentlight receptors in the human eyerespond to the entire visiblespectrum when looking at an objectit is common to use amultiwavelength instrument such asa grating spectrometer.



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Real life application of diffraction grating

The diffraction grating is animmensely useful tool for theseparation of the spectral linesassociated with atomictransitions. It acts as a "superprism", separating the different

colors of light much more thanthe dispersion effect in a prism.The illustration shows thehydrogen spectrum. Thehydrogen gas in a thin glass tubeis excited by an electrical

discharge and the spectrum canbe viewed through the grating.

http://hyperphysics.phy-astr.gsu.edu/hbase/hyde.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/hyde.html


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Electro-optic effect:when an electric field Is applied across an optical medium the distribution of

electrons within it is distorted so that the polarizability and hence the refractive

index of the medium changes anisotropically. The result of this electro-optic

effect may be to introduce new optic axes into naturally doubly refracting

crystalse.g. KDP,GaS



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Acousto-optic effect: theacousto-optic effect is the change in

the refractive index of a medium

caused by the mechanical strains

accompanying the passage of an

acousic(strain) wave through themedium.


Acousto-Optics:

h f i i d f i l di i l d b


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The refractive index of an optical medium is altered by

the presence of sound; sound modifies the effect of

medium on light; Many useful devices make use of this acousto optic

effect: optical modulator,switches, deflectors, filters,

isolators, frequency shifters, and spectrum analyzers.

Sound is a dynamic strain involving molecularvibrations that take the form of waves which travel at a

velocity characteristic of the medium; vibration of

molecular => polarizability => refractive indexx

z

=2/s in

Bragg diffraction: an

acoustic plane

wave acts as a partial

reflector of light

beams litter .ANUJ BHARDWAJ (UNIT-1) 90

Interaction of light and sound:

B Diff i


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Bragg Diffraction:

Consider an acoustic plane wave traveling in thex

direction in a medium with velocity vs, frequencyf,and wavelength = vs/f. The strain (relative

displacement) at positionx and time tis

)c o s (),(0 q xtstxs -=

s0: amplitude; = 2f; q = 2/ (wavenumber).

The acoustic intensity (W/m2) is 2/2

0

3svI ss =

: mass density of medium.

The medium is assumed to be optical transparent and

the refractive index in the absence of sound is n. The

strain s => perturbation of the refractive index

(analogous to the Pockels effect)

),(),(3

21

txsntxn p-=Dp: photoelastic constant

(strain-optic coefficient)ANUJ BHARDWAJ (UNIT-1) 91


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Magneto-optic devices:the presence of magnetic fields may

also affect the optical properties of

some substances thereby giving rise

to a number of useful devices.This is

based on the faraday effect.


Assignment


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Assignment

Discuss basic light sources and its characterisation.

What is Bire frengence? How it is useful to generate electro-

optic effect.

What is Acousto optic effect? Explain Raman Nath effect.

How magneto optic effect is used to design current

sensors.Explain with relevant diagram.

What is Diffraction grating? Write down its application.

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