OPTICAL TRAPPING OF MESOSCOPIC TRANSPARENT/METALLIC

PARTICLES BY SPATIALLY STRUCTURED LASER BEAM AND

CHARACTERIZATION OF TRAPPED RBCs

by

RANJEET KUMAR

INSTRUMENT DESIGN DEVELOPMENT CENTRE

Submitted

in fulfilment of the requirement of the degree of Doctor of Philosophy

to the

INDIAN INSTITUTE OF TECHNOLOGY DELHI, INDIA

AUGUST, 2011

CERTIFICATE

This is to certify that the thesis entitled "OPTICAL TRAPPING OF MESOSCOPIC

TRANSPARENT/METALLIC PARTICLES BY SPATIALLY STRUCTURED

LASER BEAM AND CHARACTERIZATION OF TRAPPED RBCS" is being

submitted by RANJEET KUMAR to the Instrument Design Development Centre, Indian

Institute of Technology Delhi, for the award of the degree of DOCTOR OF

PHILOSOPHY. This thesis is a record of bona-fide work carried out by him under my

guidance and supervision. In my opinion the thesis has reached the standards fulfilling the

requirements for the submission relating to the degree.

The results contained in this thesis have not been submitted to any other University/Institute

for the award of any degree or diploma.

Advisors,

Dr. Dalip Singh Mehta

INSTRUMENT DESIGN DEVELOPMENT CENTRE

Prof. Chandra Shakher

INSTRUMENT DESIGN DEVELOPMENT CENTRE

INDIAN INSTITUTE OF TECHNOLOGY DELHI

INDIAN INSTITUTE OF TECHNOLOGY DELHI

ACKNOWLEDGEMENTS

I am indebted to my advisors Dr. Dalip Singh Mehta and Prof. Chandra Shakher

for their endless enthusiasm, ideas and altruistic environment they have provided me

continuously during the last five years. Special thanks extend to examiners who made thesis

more illustrative and coherent from their invaluable comments/suggestions.

Many faces have come into and gone during my research sortie but they have left

inerasable imprints. Name-checking of every one would be a tall list but they really deserve

the recognition.

My special thanks extend to other side of the center, to Prof. P. Senthilkumaran in

the Department of Physics for his support of supplementary experimental facilities. Ever

since I first met with Prof. Hitendra Kumar Malik from the same department, his

guidelines have energized me to embrace a career in academics. Thanksgiving includes my

senior Dr. Pradeep Kumar Kushwaha and Dr. Satish Kumar Dubey who constantly

encouraged and kept-on revitalizing me during odd hours. I'd like to thank my junior

colleagues Mr. Vishal Shrivastava being easy in analysing the data through MATLAB and

Dr. Jai Prakash Rana for providing the Mylar spacer — a key part of sample-cell

preparation. My special thanks extend to a gang of colleagues Ms. Tulsi Anna, Dr. Manoj

Kumar Singh, Dr. Manish Aggrawal, Dr. Arvind Sinha, Ms. Gurvinder Sehgal, Mr.

Gyanendra and Mr. Mohammad Inam for making the Ph.D. sortie merriment including a

friend beyond the premises of Indian Institute of Technology Delhi who provided me

Ehrlich ascites carcinoma cells (EAC).

iv

I would like to thank the supportive staff members of central workshop, especially

Raja Ram who helped me whenever I was in the need of any supplementary part of

experiment to execute optical trapping.

The science promoting organisations in INDIA like DST & CSIR are also greatly

thanked who have extended their financial support in attending the International conferences

in U.S.A. (2009) and FINLAND (2010) for the pursuit of excellence and career development.

More personally I pay my obeisance to my parents: Smt. Shiv Devi & Shri

JangBahadur Singh for their unconditional love, encouragement and moral support. My

sweet younger brother Mr. Ashish Kumar has given his shoulders keeping me away from

the responsibilities during my absence. I could remember each fables taught to me by my late

Grand-parents for the pursuit of essence of a successful human being and her rear during

childhood. This thesis is dedicated to you...

Ranjeet Xumar

V

ABSTRACT

Optical tweezer (OT) using laser light has enabled the researchers to carry-out fundamental studies and peep into the microscopic world of natural sciences and engineering. In this thesis, multiparticle trapping of metallic nanostructures, photodamage-free isolation of electrically anisotropic rod-shaped live single cells E. coli bacteria and biological cells like RBCs and EAC cells, and then their characterisation using spatially structured and asymmetric (SSA) laser beam have been presented in seven chapters.

In Chapter 1 Fundamentals of optical tweezers (OT), radiation pressure, classification of the working regimes based on trapping wavelength and particles size, forces involved in OTs acting on transparent as well as metallic particles, development of OT, need of spatial beam shaping techniques (SLM, CHGs, e-beam lithographic phase-plate, multiple beam interferometry, holography etc.) and their merits and demerits in optical trapping schemes and up-to-date literature review is covered. Factors, like state of polarization of laser beam, aberrations of the optical system and the consequences of excitation of plasmon waves influencing the light-matter interaction in trapping have been discussed. Predominantly, the central role of SSA laser beam in multiparticle trapping has been augmented.

In Chapter 2 Generation of spatial beam patterns from fundamental mode TEMoo (also LPo1 )

emitted from red He-Ne laser light (Milles Garriot) using a 1x2 single mode fiber-coupler (SMFC) has been described. Here it has been investigated that due to presence of birefringence as a result of either of fibre-core asymmetry or a stress-induced waveguide cause the generation of LP 1 modes. Further, spiral pattern of unit charge (sometimes more than one) obtained by interfering LPo 1 and LP 1 modes at beam-splitter is demonstrated for real-time observation of minuscule power-fluctuations of a laser source (2mW, 532nm).

In Chapter 3 Multiparticle trapping and assembling of polystyrene beads using SSA laser

beam emitted directly from the cavity of diode pumped solid state (Nd 3+ : YVO4 ) laser source (Laser Glow, Canada) operating at 532nm is described. It has been analysed that distributed intensity gradients of SSA beam has generated relatively larger focused spot size than pure TEMoomode, smearing out the centrally confined power which in-turn effected weaker axial scattering force. SSA laser beam (p — polarization) driven OT has achieved in real-time photodamage-free multiple trapping of anisotropic rod-shaped live-microorganisms.

Chapter 4 In-situ clustering of unfunctionalized large diameter Au-NP (150nm and 254nm) by SSA laser beam near plasmon excitation wavelength window has been demonstrated. This

Vi

has been achieved because SSA beam has reduced the destabilizing axial-scattering force and created distributed potential wells corresponding to intensity gradients enough to trap the Au-NPs at the lowest reported value of trapping power so far (9.6mW). Therefore, first Ehrlich ascites carcinoma (EAC) cell was trapped in a sample containing unfunctionalized but distributed Au-NPs (254nm) and multiply enhanced scattering of trapping beam was observed — a confirmation of in-situ cluster formation. This study can be used for sensing, imaging, assessing the state of tumor/cancer progression, efficacy assessment of targeted load-delivery, phototherapy, non-linear spectroscopy and SERS etc.

In Chapter 5 Real-time line-pattern formation from trapped polystyrene spheres and tiny clusters of SDBS-functionalized single walled carbon nanotubes (SWCNTs) along the bright and dark region of fringes respectively using a crude, simple and cost-effective Michelson type interferometric optical tweezer (IOT) is presented. IOT is developed by coating a highly reflecting layer (-100nm thick by vapour deposition method) on one surface of cubic beam splitter which has freedom of changing the fringe-pitch and their orientation simultaneously. Despite the trapping wavelength (532nm) being blue-detuned with respect to two absorption peaks of SWCNTs (516nm and 545nm), this has been realized due to alternate intensity regions of Interferometric beam.

In Chapter 6 Simultaneous Euler buckling-free (threshold laser power for Euler buckling at object plane is 4.2mW) trapping of human red blood cells (RBCs) by SSA laser beam driven OT and IOT for their morphometry is investigated. Trapping of RBCs using SSA laser beam found two fold advantages. One, RBCs were trapped stably without causing any photodamage (computed threshold power at sample was 3.64mW- less than threshold value). Second, undesirable perturbations often induced into RBCs from the direct physical contact with glass-substrate to make them stationary in frequently employed techniques for morphometry, has been overcome. Morphology and refractive index (RI) of thus trapped RBC was measurement using fringe projection and phase-retrieval techniques. The obtained values of RI using this scheme are found close to standard values.

Chapter 7 provides conclusion of the research work presented in the thesis and perspectives of future work.

DecCicatedito,

My parents antifamily members

and

VII

In the memory of my Grand=parents

ix

TABLE OF CONTENTS

Certificate I

Acknowledgements III

Abstract V

List of Figures XIV

List of Tables XX

Chapter 1: INTRODUCTION 1-34

1.1 Prologue 1

1.2 Radiation pressure 2

1.3 Optical tweezers (OT) 4

1.4 Forces involved in OT on transparent spherical particles 6

1.4.1 Geometrical optics regime (Ray-optics model) 7

1.4.2 Rayleigh regime (Dipole moment approach) 8

1.5 Laser — metallic-nanoparticles interaction and forces 10

1.5.1 Surface plasmons 10

1.5.2 The evanescent wave 10

1.5.3 Optical forces 14

1.6 Need and applications of OT 18

1.7 Basic OT set-up and its advancement 19

1.8 General theory of effects of aberrations on focussing and imaging 22

1.9 Influence of polarisation state of laser and its consequences on trapping 25

1.10 Need of spatial beam shaping/sculpting and its pros and cons 27

x

1.11 Cavity generated SSA laser beam and size of focused spot 30

Chapter 2: GENERATION OF OPTICAL VORTEX BEAM USING SINGLE MODE FIBER OPTIC Y COUPLER AND ITS APPLICATION 3 5-47

2.1 Introduction 35

2.2 Mode characteristics in SMF

37

2.3 Core asymmetry/stress-induced birefringence for generation of LP m modes

in fiber Y-coupler w 2.4 Experimental details and results discussion 41

2.5 Application of spiral pattern for real-time observation of power-fluctuations

of lasers 47

2.6 Conclusion 50

Chapter 3: MULTIPARTICLE TRAPPING OF POLYSTYRENE BEADS AND ROD-SHAPED SINGLE CELL E.Coli MICROORGANISM USING SPATIALLY STRUCTURED AND ASYMMETRIC LASER BEAM 49-63

3.1 Introduction 49

3.2 Brief theory of field at focused spot 51

3.3 Computational analysis 53

3.1.1 Trapping forces on polystyrene beads under straight-ray model 53

3.1.2 Trapping forces on polystyrene beads under parabolic-ray model 54

3.4 Experimental details 55

xi

3.5 Results and discussion 57

3.6 Application of SSA laser beam for multiple trapping of cylindrical

prokaryote E. coli bacteria 61

3.7 Conclusion 63

Chapter4: SPATIALLY STRUCTURED AND ASYMMETRIC LASER BEAM FOR In-Situ CLUSTERING OF PLASMONIC Au-NPs AND ASSISTED In-Vitro CHARACTERIZATION OF EHRLICH ASCITES CARCINOMA CELLS 65-95

4.1 Introduction G

4.2 Theories and methods of calculation of trapping forces 68

4.3 Evaluations of the components of trapping forces 72

4.3.1 Radiation forces and trapping efficiencies for 254nm diameter Au-N72

4.3.2 Change of temperature-profile of 254nm diameter Au-NPs in

surrounding medium 73

4.3.3 Radiation forces and trapping efficiencies for 150nm diameter Au-N75

4.3.4 Change of temperature-profile of 150nm diameter Au-NPs in

surrounding medium 75

4.4 Experimental details 78

4.5 Results and discussion 79

4.5.1 Role of SSA laser beam 79

4.5.2 Role of near and far-field trapping efficiencies 81

4.5.3 Role of thermophoresis and convective forces 83

4.6 SSA laser beam for intra-cellular clustering of Au-NPs within EAC cells 85

xii

4.7.1 Mechanism of assembling of Au-NPs near plasmon excitation in OT 87

4.7.2 Material and EAC cells 90

4.7.3 Experimental details 92

4.7.4 Results and discussion 92

4.7 Conclusion 95

CHAPTER 5: INTERFEROMETRIC OPTICAL TWEEZERS FOR PATTERNED TRAPPING AND MANIPULATION OF POLYSTYRENE SPHERES AND SWCNTS 97-106

5.1 Introduction 97

5.2 Details of interferometric optical tweezers 99

5.3 Optical characterization of coating surface 101

5.4 Experimental procedure and results discussion 101

5.4.1 Experimental set- up 101

5.4.2 Trapping and manipulation of polystyrene micro-particles 102

5.4.3 Linear aggregation of SWCNTs clusters 104

5.5 Conclusion 106

CHAPTER 6: ASSIMILATION OF EULER BUCKLING-FREE OPTICAL TRAPPING WITH INTERFEROMETRY TO RETRIEVE MORPHOMETRY AND REFRACTIVE INDEX MESUREMENT OF RBC 107-120

6.1 Introduction 107

6.2 Optical characterisation techniques of RBCs 107

6.3 Shape and dynamics of RBC under laser-light in OT 109

6.4 Interferometric fringe projection profilometry and phase retrieval 112

6.5 Experimental set-up and procedure 114

6.6 Results and discussion 114

6.7 Conclusion 120

CHAPTER 7: CONCLUSION AND SCOPE FOR FUTURE WORK

121-124 Conclusion 121-122

Scope of the present study for future work 123-124

REFRENCES: 125-170