journal club 23rd march 2011 - windows

8/2/2019 Journal Club 23rd March 2011 - Windows

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OU :: Department of Physics &

Astronomy :: Journal Club

Alexander Baker23rd March 2011


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Propagation dynamics of optical

vortices .Journal of Optical Society of America B/Volume14th3054-3065 (Nov1997).

D. RozasDepartment of Physics, Worcester Polytechnic

Institute, Worcester, Massachusetts.C. T. LawDepartment of Electrical Engineering and

Computer Science, University of Wisconsin, Milwaukee.

G. A. Swartzlander, Jr. Department of Physics, Worcester

Polytechnic Institute, Worcester, Massachusetts.

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University College London

Department of Physics & Astronomy, Dr PhillipJones

Optical Tweezers Group

Summer project to investigate a numerical model for

the propagation of OVs in linear and non linearmediums.

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Contents

Section 1: Background & Introduction Section 2: Review of definitions

Section 3: Analytical descriptions of the propagation

dynamics

Section 4: Numerical and revised theoretical analysesfor special cases

Section 5: Conclusions

UCL Model, demonstration and findings

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Section 1: Background

Optical Vortex Light can be twisted like a corkscrew around its axis

of travel, light waves at the axis cancel each other out.

Projected ring of light.

Topological Charge.

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Section 1: Introduction

Dynamics similar to hydrodynamic vortexphenomena.

Develop intuitive understanding of OV motion.

Describe propagation dynamics of different types of

vortices. Applications in Optical Tweezers, Exoplanet

detection, Quantum Computing.

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Section 2: Definitions and Properties of

OVs.

Field of single

vortex with Ansatz

G_{bg} - Gaussianprofile.

Compare and

contrast two core

functions.

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Section 3 : Analytics Descriptions of

the propagation dynamics.

Scalar paraxial

propagation, linear

and nonlinear. Phase and intensity

gradient

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Section 3.1 : Gaussian beam dynamics.

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Phase increases 2pi

clockwise both cores.

No rotation found

around optical axis.


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Section 4: Numerical analyses

for special cases

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Split step or beam

propagation method.

Linear and non linear

terms.


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Three factors that affect motion of optical vortices Amplitude gradient

Phase gradient

non linear factordepends on intensity gradient

Contrasting differences between r and tanh corefunctions.

Discuss 4 different cases

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Case 1: Linear vortexLinear propagation of a vortex placed in the centre of a

Gaussian beam.

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Diffraction ringing

may occur in near

field


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Case 2: Nonzero background gradientDisplaced vortex from the centre of the beam to location

with non zero background gradient

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Single tanh vortex

expected to move in

straight line

propagation.


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Case 3: Second vortexIntroduce a second vortex, trajectory affected by Gaussian

field and field of second vortex.

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R vortex no

rotation.

Pair of tanh

vortices significant

rotation


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Case 3: Second vortexIntroduce a second vortex, trajectory affected by Gaussian

field and field of second vortex.

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Case 4: Nonlinear mediaIntroduce self-defocusing non linear medium.

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Three factors that affect motion of optical vortices Amplitude gradient

Phase gradient

non linear factordepends on intensity gradient

Contrasting differences between r and tanh corefunctions.

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UCL Model & Findings ::

animations

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OU :: Department of Physics &

Astronomy :: Journal Club


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Appendix A : Geometry.

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Ginzburg and

Pitaevskii.

Scalar paraxial

propagation, linear

and nonlinear.

Hydrodynamic

paradigms describe

EM phenomena

Phase and intensity

gradient.

journal club 23rd march 2011 - windows

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