Light: Its Applications in interometery, polarimetry and photodynamic therapy

Masroor IkramMay 13, 2010

Pakistan Institute of Engineering and Applied Sciences

Light ?• By the end of nineteenth century wave nature of

light was well accepted and there was a slogan that all the problems related to optics have been solved except to prove ether.

• In 1887 well-known Michelson-Morley experiment disprove the concept of ether.

• Earlier black-body radiation and in 1905 the famous paper of photoelectric effect forced scientists to rethink particle nature of light.

• Since then light is considered to has dual nature.

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

asked to describe an elephant. – One blind man touched the elephant’s tail and

said the elephant was long and thin like a rope.

– The second blind man touched the elephant’s leg and described the elephant as round and hard like a tree trunk.

– The third man felt an ear and said that the elephant was thin and flat, like a huge leaf.

Each man’s description was correct, but didn’t give the complete picture.

• Scientists who study the nature of light are like the blind men in the story. They try to describe light, but their 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 four centuries, light is sometimes considered as particle and sometimes as wave, now scientists agreed on its dual nature.

Einstein in Optics and Lasers

• Einstein is famous for relativity but his contributions in optics and lasers are also fundamental.

• In 1905, photoelectric effect shaken the basics of the theory of light and Einstein was awarded Nobel prize for it.

• In 1916-17, he published two papers describing the stimulated emission, which was experimentally demonstrated in MASER during 1950s and led the foundations of LASER.

Interferometry

Michelson Interferometer• The Michelson interferometer

is the most common configuration for optical interferometry. The interference pattern produced depends on the path difference between the two beams.

• Michelson & Morley used this interferometer for their famous experiment (1887) in which this interferometer was used to disprove the concept of ether.

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.

Carousel Interferometer

G. Hussain and M. Ikram, Optimization of linearity by use of a glass plate in carousel interferometers, Opt. Letts. 29(16) 1930-32, 2004.

Angle and Axis of

Rotation MeasurementG. 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: A Detailed Analysis, Appl. Opt. 49(6) 1025-1031, 2010.

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.

Intensity modulation of the laser beam profile due to vibration of the objective is demodulated to give the amplitude and frequency of vibration.

Optical Coherence Tomography

• Optical Coherence Tomography (OCT) performs imaging by measuring the echo time 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

• OCT is capable of high temporal resolution allowing the study of dynamic physiologic features

• Optical measurements can be performed exceedingly fast (<ns).

• OCT provides relatively low spatial resolution because of the physics of light propagation in turbid media

• The penetration range of light in tissue limits the size of the target tissue volume.

• Light intensity is heavily attenuated in tissue and falls off exponentially.

Experimental Setup of OCT

PolarimetryPolarization sensitive optical imaging

I' = M I

M = 4 x 4 Mueller Matrix

θI

I'

Laser

M

IQUV

Total Intensity

I =

Scatterer, represented by Mueller matrix,

Incident beam

Scattering Angle

ScatteredBeam

Circular Polarization± 45°0°,90° Polarization

Polarization Imaging

detector

sample cell

polarizer

Light source

plane isrotated analyzer

aaplane-polarizedlight

observedrotation

00000

rotate to null

A Simple Polarimeter

Stokes Vector

−−−+

=

=−+

LCPRCP

VH

VH

IIIIIIII

SSSS

s4545

3

2

1

0

To determine the properties of emergingbeam, one multiplies the vectors describingthe incident beam with Mueller matrices. Ingeneral, the interaction of light with opticalelements such as lenses, polarizers, filters,surfaces, scattering media etc, changes thepolarization state of the light, when itdescribed by a four-component vector,[S0,S1,S2,S3], interacting with any optical element or material .

[Sout] = [Msystem].[Sin]

Mueller Matrix

Curve fits for the calculation of unknown coefficients

Photo-detector

Polarizerat 45o

with E

Analyzerat -45o

with 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 axisZ axis

Material characterization with polarized laser light (Kerr Cell )

0 1000 2000 3000 4000 5000 6000

0.0

0.2

0.4

0.6

0.8

1.0

Applied Voltage (V)

Norm

alize

d Tr

ansm

ittanc

e

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

Depolarization of light from nitrobenzene

0 1000 2000 3000 4000 5000

0.0

0.2

0.4

0.6

0.8

1.0

θι = 45o, θο = -45o

Norm

alize

d Tr

ansm

ittan

ce

Applied Voltage (volt)

θι = 45o, θο = 45o

θι = 0ο, θο = 0ο

Curve fit for θι = 0ο, θο = 0ο

θι = 0ο, θο = 90ο

Curve fit for θι = 0ο, θο = 90ο

Estimate of MaxI45,45 Curve fit for MaxI45,45

Estimate of MinI45,45 Curve fit of MinI45,45

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

Characterization Of UHMWPE Using Mueller 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 ofmaterial 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.

Optical Biopsy

Photodynamic TherapyCancer Treatment with Lasers

• Two individually non-toxic components brought together to cause harmful effects on cells and tissues in the presence of oxygen– Photosensitizing

agent

– Light of specific

wavelength

Process of Photodynamic Therapy

Illustration of the Process

The photosensitiser is given by injection.

After time the photosensitiser concentrates in the tumor.

The photosensitiser is activated by light

The tumor is selectively destroyed

Mechanism

Celular destruction

Epidermis

Basal cell carcinoma

5-AminolevulinicAcid

selectivetumor necrosis

Topical PDT

In Vitro Studies of PDT on HeLa and Hep2c Cell Lines

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

• HeLa cells were grown with 5-ALA photosensitizer in the laboratory of National Institute of Health, Islamabad.

• The primary focus of the experimental work was to study he efficacy of ALA mediated photodynamic effects in HeLa cells.

-20 0 20 40 60 80 100 120 140 160

20

40

60

80

100

120%

Viab

ility

ALA Concentration (µg/ml)

50 J/cm2

0 J/cm2

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

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

0 50 100 150 200 250

20

30

40

50

60

70

80

90

100

110

% V

iabi

lity

ALA concentration, µg/ml

85J/cm2

0J/cm2

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

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

Photodynamic Therapy: In Action

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

After 72 hours

After 1 week

After 4 weeks

Aktinic Keratosis

Diagnosis:“Basal cell carcinoma (Nose)” and Actinic Keratosis ( Left Cheek ).

Treatment: Two (02) sessions of PDT given .

Remarks:Gross tumor clearance with good

cosmetic outcome.

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

34

After 4 weeks

35

Before Treatment

After Treatment...72 hours After 4 weeks

AQ , 53 years male , resident of PeshawarDiagnosis:

“Basal Cell Carcinoma ( left eye medial canthus )”

Treatment :Excision Biopsy done

Two sessions of PDT given for positive margins

Remarks:09 months recurrence free period

with good cosmetic outcome.

Histopathological clearance also seen on re-biopsy

at 9 months follow up in Peshawar dated 27-11-08

reported as “No evidence of malignancy found .“

36

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 one has no response.

• Currently we have treated only superficial skin cancers but planned to start for internal cancers using inject able photosensitizer and endoscope.

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