GENERATION OF VERSATILE VORTEX LINEAR LIGHT BULLETS Thesis Submitted to The School of Engineering of the UNIVERSITY OF DAYTON In Partial Fulfillment of the Requirements for The Degree of Master of Science in Electro-Optics By Xin Huang UNIVERSITY OF DAYTON Dayton, Ohio December, 2015 GENERATION OF VERSATILE VORTEX LINEAR LIGHT BULLETS Name: Huang, Xin APPROVED BY: ________________________________ ______________________________ Andy C. Chong, Ph.D. Imad Agha, Ph.D. Advisory Committee Chairman Committee Member Assistant Professor Assistant Professor Physics Department and Physics Department and Electro-Optics Graduate Program Electro-Optics Graduate Program _____________________________ Joseph W. Haus, Ph.D. Committee Member Professor Electro-Optics Graduate Program ________________________________ ___________________________ John G. Weber, Ph.D. Eddy M. Rojas, Ph.D., M.A., P.E. Associate Dean Dean School of Engineering School of Engineering ii © Copyright by Xin Huang All rights reserved 2015 iii ABSTRACT GENERATION OF VERSATILE VORTEX LINEAR LIGHT BULLETS Name: Huang, Xin University of Dayton Advisor: Dr. Andy C. Chong We demonstrate a versatile vortex linear light bullet as a three-dimensional vortex Airy- Bessel wave packet for the first time. It combines a temporal Airy pulse with a higher order vortex Bessel beam in the spatial domain. Its non-varying feature in linear propagation is verified by three-dimensional (3D) measurements. Advanced from previously reported linear light bullets which are limited to specific materials, the vortex Airy-Bessel wave packet works as a light bullet for any material while carrying orbital angular momentum. It is believed that the versatile vortex linear light bullet is useful in many applications such as nano-lithography, nano-surgery, etc. The study of controlled collisions between optical vortices in the time domain is also reported in this thesis. iv Dedicated to my parents and my girlfriend Veronique DEDICATION v ACKNOWLEDGEMENTS I would like to express my special appreciation to my advisor Dr. Andy Chong, you have been a wonderful mentor for me. I would like to thank you for encouraging my research and for allowing me to grow as a researcher in past two years. Your advice on both research as well as on life have been invaluable. I would also like to sincerely thank my committee members, Prof. Haus and Dr. Agha for serving as my committee members. Thank you for the encouragements and suggestions. I also want to thank Prof. Zhan for assistance. I would also like to thank my group members: Qian Cao, Chenchen Wan, Peiyun Li and other lovely friends in Electro-Optics Program, who have made valued contributions on my research. I really enjoy studying and working with you. A special thanks to my family. I have a warm loving family. Their support has been powerful all the time, they encourage me every single moment and support me whenever I need it. I really appreciate their caring and loving me as I grow up. vi TABLE OF CONTENTS ABSTRACT ................................................................................................................................... iv DEDICATION ................................................................................................................................. v ACKNOWLEDGEMENTS ............................................................................................................ vi LIST OF FIGURES ........................................................................................................................ ix LIST OF ABBREVIATIONS AND NOTATIONS ....................................................................... xi CHAPTER I INTRODUCTION ..................................................................................................... 1 1.1 Organization of the thesis ...................................................................................................... 1 1.2 Optical spatio-temporal wave packets and linear light bullets............................................... 2 CHAPTER II THEORETICAL BACKGROUND ......................................................................... 7 2.1 Spatio-temporal wave packets ............................................................................................... 7 2.2 Group velocity dispersion and diffraction ............................................................................. 9 2.3 Airy pulses ........................................................................................................................... 13 2.4 Bessel beams ........................................................................................................................ 16 2.5 Optical vortices .................................................................................................................... 18 2.6 Optical vortex Airy-Bessel wave packets ............................................................................ 19 2.7 Collisions between vortices in both the spatial and the temporal domains .......................... 20 CHAPTER III EXPERIMENTAL SYSTEM ............................................................................... 25 3.1 Pulse characterization .......................................................................................................... 25 3.2 Pulse shaping ....................................................................................................................... 28 3.3 Beam shaping ....................................................................................................................... 32 3.4 Three-dimensional measurement method ............................................................................ 33 CHAPTER IV EXPERIMENTAL RESULTS ............................................................................. 37 vii 4.1 Experimental setup for the vortex Airy-Bessel wave packet ............................................... 37 4.2 Experimental results for linear propagation dynamics of vortex Airy-Bessel wave packets ................................................................................................................................................... 38 4.3 Experimental setup for collision between vortices in the temporal domain ........................ 42 CHAPTER V CONCLUSIONS ................................................................................................... 45 BIBLIOGRAPHY .......................................................................................................................... 46 viii LIST OF FIGURES Figure 2.1 Propagation of a Gaussian pulse through a dispersive medium ............................................. 10 Figure 2.2 Spreading of a 3D spatio-temporal wave packet due to dispersion and diffraction ..... 13 Figure 2.3 Simulated results for an Airy pulse (b) converted from a Gaussian pulse (a). a >0 ..... 14 Figure 2.4 Simulated results for an Airy pulse and a Gaussian pulse propagating in a dispersive medium with normal dispersion ..................................................................................................... 16 Figure 2.5 Generation of a zero-order Bessel beam using an axicon lens ..................................... 17 Figure 2.6 Simulated results for a zero-order Bessel beam generated by an appropriate axicon lens ................................................................................................................................................. 18 Figure 2.7 LG modes with different topological charges .............................................................. 19 Figure 2.8 Generation of LG modes using a hologram mask ........................................................ 19 Figure 2.9 Formation of the vortex Airy-Bessel wave packet ....................................................... 20 Figure 2.10 Interactions of spatially colliding vortex Airy beams with same topological charges when propagating along z axis ....................................................................................................... 22 Figure 2.11 Interactions of spatially colliding vortex Airy beams with opposite topological charges when propagating along z axis ......................................................................................... 22 Figure 2.12 Simulated 3D collision between a vortex Gaussian-LG wave packet and a vortex Airy-LG wave packet with same and opposite unitary topological charges .................................. 23 Figure 2.13 Collisions with a little transverse misalignment between two wave packets carrying vortices with opposite unitary charges ............................................................................ 24 Figure 3.1 The setup for measuring interferometric AC for collinear SHG geometry ................. 26 ix Figure 3.2 Simulation of an interferometric AC signal ................................................................. 28 Figure 3.3 General setup for modulator based pulse shaping ........................................................ 29 Figure 3.4 Basic layout of SLM with single layer used for pulse shaping .................................... 31 Figure 3.5 Side view of a liquid crystal pixel ................................................................................ 31 Figure 3.6 Conceptual setup for real space beam shaping using SLM .......................................... 33 Figure 3.7 Conceptual setup for 3D measurement system............................................................. 34 Figure 4.1 Experimental setup to generate