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Light: Its Applications in interometery, polarimetry and photodynamic therapy

Masroor IkramMay 13, 2010

Pakistan Institute of Engineering and Applied Sciences


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Light ? By the end of nineteenth century wave nature of

light was well accepted and there was a slogan thatall the problems related to optics have been solvedexcept to prove ether.

In 1887 well-known Michelson-Morley experimentdisprove the concept of ether.

Earlier black-body radiation and in 1905 the famouspaper of photoelectric effect forced scientists torethink particle nature of light.

Since then light is considered to has dual nature.


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Light is an elephant An old story tells of three blind men who were

asked to describe an elephant. One blind man touched the elephants tail and

said the elephant was long and thin like a rope.

The second blind man touched the elephants legand described the elephant as round and hard likea tree trunk.

The third man felt an ear and said that theelephant was thin and flat, like a huge leaf.Each mans description was correct, but didntgive the complete picture.


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Scientists who study the nature of light are like theblind men in the story. They try to describe light, buttheir descriptions depend very much on which

aspects of light they study. Each description of light is merely an approximation

to the reality that is light. During the last fourcenturies, light is sometimes considered as particleand sometimes as wave, now scientists agreed on itsdual nature.


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Einstein in Optics and Lasers

Einstein is famous for relativity but hiscontributions in optics and lasers are alsofundamental.

In 1905, photoelectric effect shaken the basicsof the theory of light and Einstein was awardedNobel prize for it.

In 1916-17, he published two papers describingthe stimulated emission, which wasexperimentally demonstrated in MASER during1950s and led the foundations of LASER.


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Interferometry


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Michelson Interferometer

The Michelson interferometeris the most commonconfiguration for opticalinterferometry. Theinterference pattern produceddepends on the pathdifference between the twobeams.

Michelson & Morley used this

interferometer for theirfamous experiment (1887) inwhich this interferometer wasused to disprove the conceptof ether.


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Novel Interferometersfor precision angle and axis of rotation measurements

M. Ikram and G. Hussain, Michelson interferometer for precision angle measurements ,Appl. Opt. 38(1) 113-120, 1999.


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CarouselInterferometer

G. Hussain and M. Ikram, Optimization of

linearity by use of a glass plate in carousel interferometers , Opt. Letts. 29(16) 1930-32, 2004.


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Angle andAxis of

RotationMeasurementG. Hussain and M. Ikram,

Optical Measurements of Angle and Axis of Rotation , Opt. Lett. 33 (21)2419-21, 2008.

G. Hussain and M. Ikram,Measurements of Angle and Axis of Rotation in a Carousel Interferometer: ADetailed Analysis , Appl.Opt. 49(6) 1025-1031, 2010.


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Vibration Detection with Lasers

A. Hussain, S. K. Ayazuddin, M. Ikram , A. A. Mudassar, A. A. Qureshi, and M. Iqbal, Remote

sensing for flow induced vibrations in PARR-1 core assembly , Nucl. Engg. Design 205 (3) 323-31, 2001.

Intensitymodulation of thelaser beamprofile due tovibration of theobjective isdemodulated togive theamplitude and

frequency of vibration.


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Optical Coherence Tomography

Optical Coherence Tomography (OCT)performs imaging by measuring the echotime delay and magnitude of back reflected

or backscattered light using interferometry. The most common detection method is

based upon a Michelson interferometer with

a scanning reference arm. In OCT low coherence light source is used,

e.g. Ti: Sapphire laser or SLDs


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OCT is capable of high temporal resolutionallowing the study of dynamic physiologicfeatures

Optical measurements can be performedexceedingly fast (


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Experimental Setup of OCT


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PolarimetryPolarization sensitive optical imaging


16/38I' = M I

M = 4 x 4 Mueller Matrix

II'

Laser

M

IQUV

Total Intensity

I =

Scatterer, representedby Mueller matrix,

Incident beam

ScatteringAngle

ScatteredBeam

Circular Polarization 45 0,90Polarization

Polarization Imaging


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detector

sample cell

polarizer

Light source

plane isrotated analyzer

aaplane-polarizedlight

observedrotation

00000

rotate to null

A Simple Polarimeter


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Stokes Vector

+

==+

LCP RCP

V H

V H

I I

I I I I

I I

S

SS

S

s4545

3

2

1

0


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To determine the properties of emergingbeam, one multiplies the vectors describingthe incident beam with Mueller matrices. Ingeneral, the interaction of light with optical

elements such as lenses, polarizers, filters,surfaces, scattering media etc, changes thepolarization state of the light, when itdescribed by a four-component vector,[S 0 ,S 1,S 2 ,S 3 ], interacting with any opticalelement or material .

[S out ] = [ Msystem ].[S in]

Mueller Matrix


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Curve fits for the calculation of unknowncoefficients

Photo-detector

Polarizerat 45owith E

Analyzerat -45owith E

Melles GriotM/N 05-LHP-1115mW Max Output

= 632.8 nm

Plate

Lenses fordiverging the

light

Kerr CellL

dTerminalsfor Voltage

Ea Y axis

X axis

Z axis

Material characterization withpolarized laser light (Kerr Cell )


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0 1000 2000 3000 4000 5000 60000.0

0.2

0.4

0.6

0.8

1.0

Applied Voltage (V)

N o r m a l i z e d T r a n s m i t t a n c e

Solid curve is the simulated result of traditional expression for intensitytransmittance where as filled circles is the experimental transmittance for

Nitrobenzene device


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Depolarization of light from nitrobenzene

0 1000 2000 3000 4000 5000

0.0

0.2

0.4

0.6

0.8

1.0

= 45o, = -45 o

N o r m a l

i z e d

T r a n s m

i t t a n c e

Applied Voltage (volt)

= 45 o, = 45 o

= 0 , = 0

Curve fit for = 0

, = 0

= 0 , = 90

Curve fit for = 0 , = 90

Estimate of MaxI 45,45Curve fit for MaxI 45,45

Estimate of MinI 45,45Curve fit of MinI 45,45

S. Firdous, K. Hassan and M. Ikram , Applied Optics 44(7) 1171-77 (2005)


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Characterization Of UHMWPE UsingMueller Matrix Polarimetery

Using standard Mueller Matrix Polarimeter, it is trivial toobtain 16 elements of a Mueller matrix.

In order to get some physical information from Muellermatrix, the decomposition can provide information of material parameters.

In one of the decomposition algorithm (i.e. LU-Chipmandecomposition), Mueller matrix is decomposed intosequence of three matrix factors; a di-attenuator followedby a retarder and a depolarizer.

The three matrices gives the di-attenuation, polarizance,depolarization and retardence.


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Optical Biopsy


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Photodynamic TherapyCancer Treatment with Lasers


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Two individually non-toxic componentsbrought together to cause harmful effects oncells and tissues in the presence of oxygen

Photosensitizingagent

Light of specific

wavelength

Process of Photodynamic Therapy


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Illustration of the Process

The photosensitiser is given by injection.

After time the photosensitiser concentrates in

the tumor.The photosensitiser isactivated by light

The tumor is selectivelydestroyed

Mechanism

Celulardestruction


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Epidermis

Basal cell carcinoma

5-AminolevulinicAcid

selectivetumor necrosis

Topical PDT


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In Vitro Studies of PDT on HeLa andHep2c Cell Lines

HeLa is a cell line of human cervical cancer,from a Mexican female Henrieta Lacks.

HeLa cells were grown with 5-ALAphotosensitizer in the laboratory of NationalInstitute of Health, Islamabad.

The primary focus of the experimental work

was to study he efficacy of ALA mediatedphotodynamic effects in HeLa cells.


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-20 0 20 40 60 80 100 120 140 160

20

40

60

80

100

120

% V i a b i l i t y

ALA Concentration (g/ml)

50 J/cm 2

0 J/cm 2

Comparison of Dark Cytotoxic & Phototoxic Effectsof different ALA Concentrations in HeLa Cell Line

M. Atif et.al. Laser Physics Letters 6 (12) 886-891, December 2009


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0 50 100 150 200 250

20

30

40

50

60

70

80

90

100

110

% V i a b i l i t y

ALA concentration, g/ml

85J/cm 2

0J/cm 2

Comparison of Dark Cytotoxic & Phototoxic Effectsof different ALA Concentrations in Hep2c Cell Line

A. Khurshid et.al. accepted in Laser Physics 20(7), pp--, July 2010


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Photodynamic Therapy: In Action

Profs. Hasan, Harvard Medical School and Georgakoudi,Tufts University, are observing the skin cancer treatmentperformed by Dr Rahmat Ullah Khan in NORI.


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After 72 hours

After 1 week

After 4 weeks

Aktinic Keratosis

Diagnosis:Basal cell carcinoma (Nose) andActinic Keratosis ( Left Cheek ).

Treatment:Two (02) sessions of PDT given .

Remarks:Gross tumor clearance with goodcosmetic outcome.

Histopathologicalclearance also seen onre-biopsy at 3 monthsfollow up in PIMS dated19-05-08 reported as Noevidence of malignancyfound.

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After 4 weeks

35

B f T t tAQ , 53 years male , resident of Peshawar


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Before Treatment

After Treatment...72 hours After 4 weeks

Diagnosis:Basal Cell Carcinoma ( left eye medial

canthus )Treatment :

Excision Biopsy doneTwo sessions of PDT given for positive

marginsRemarks:

09 months recurrence free periodwith good

cosmetic outcome.Histopathological clearance also seen

on re-biopsyat 9 months follow up in Peshawar

dated 27-11-08

reported as No evidence ofmalignancy found .

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Summary of PDT In vitro studies on HeLa and Hep2c cell line are

carried out and published. Clinically 28 biopsy proven skin patients are treated

in PAEC Hospitals. One patient of Leishmaniaisis is

treated with positive response. Follow up shows complete response for majority of

the patients and partial response for a few and onehas no response.

Currently we have treated only superficial skincancers but planned to start for internal cancersusing inject able photosensitizer and endoscope.


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I am Thankful to: Prof. Tayyab Hasan, Harvard University, Boston, USA

Prof. Vanderlei Bagnato, University of Sao Paulo, Brazil Dr Shamaraz Firdous, NILOP Dr Rahmat Ullah Khan, PAEC General Hospital Dr Muhammad Atif, NILOP

Hafeez Ullah, PIEAS

Malik Sajjad Mehmood, PIEAS Manzoor Ahmad, PIEAS Ahmat Khurshid, PIEAS Fakhar-e-Alam, PIEAS Muhammad Imran, PIEAS Lubna Noreen, NILOP Dr Sohail Zaidi, NIH , etc.

For Their Contributions

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