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Coherent random lasing in a disordered array of amplifying microresonators A Thesis Submitted to the Tata Institute of Fundamental Research, Mumbai for the degree of Doctor of Philosophy in Physics by
Anjani Kumar Tiwari (Reg. No. – PHYS-159)
Department of Nuclear and Atomic Physics Tata Institute of Fundamental Research Mumbai September, 2014
c Copyright by
Anjani Kumar Tiwari September, 2014
DECLARATION
This thesis is a presentation of my original research work and has not been submitted earlier as a whole or in part for a degree/diploma at this or any other Institution/University. Wherever contributions of others are involved, every effort is made to indicate this clearly, with due reference to the literature, and acknowledgement of collaborative research and discussions. The work was done under the guidance of Prof. Sushil Mujumdar at the Tata Institute of Fundamental Research, Mumbai.
Anjani Kumar Tiwari [Candidate’s name and signature]
In my capacity as supervisor of the candidate’s thesis, I certify that the above statements are true to the best of my knowledge.
Prof. Sushil Mujumdar [Supervisor’s name and signature] Date: 21/04/2014 ii
ACKNOWLEDGMENTS
First and foremost, I am deeply grateful to my adviser, Prof. Sushil Mujumdar for his scientific guidance, valuable advice, support and encouragement in the journey towards my Ph.D. Working at the Nano-Optics and Mesoscopic Optics Laboratory (NOMOL) has been a great learning experience for me. I have been extremely fortunate to have some very helpful labmates, and it was a great pleasure working together in a group. I sincerely thank Balu, Bikas, Girish, Randhir, Ravitej, Swapnesh, Shadak and Sreeman. I particularly acknowledge Ravitej for his valuable help in the Monte Carlo simulations (Chapter 2) and FDTD calculations (Chapter 8). During this work, I have benefited from the discussion on various topics with Dr. Rajesh Nair and Dr. Shivakiran. I also thank Prof. Amol Dighe and Prof. R. Palit for having a keen interest in my research progress throughout my Ph.D. I express my gratitude to the DNAP office, workshop, library, photography section and university cell for their help. I thank my friends and colleagues Amaresh, Bhupender, Deepak, Pankaj, and Prashant for making my stay at TIFR a delightful and memorable experience. Last but not least, I would like to thank my parents for their constant support over the years.
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TABLE OF CONTENTS Page Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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BIBLIOGRAPHY
xxii Chapters:
1. Introduction 1.1 A short history of the random laser . . . . . . . 1.2 Conventional lasers and resonant feedback . . . 1.3 Laser-like emission from disordered media . . . 1.4 The coherent random laser . . . . . . . . . . . . 1.5 Attempts of frequency control in random lasers 1.6 Light localization . . . . . . . . . . . . . . . . . 1.7 Thesis . . . . . . . . . . . . . . . . . . . . . . .
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2. Frequency fluctuations in coherent random laser, inter-scatterer 2.1 Photon transport Monte Carlo simulations . . . . . . . . . . . . . . 2.2 Sparse system: Resonant amplifying scatterers . . . . . . . . . . . . 2.3 Dense scattering system . . . . . . . . . . . . . . . . . . . . . . . . 2.4 A practical proposal . . . . . . . . . . . . . . . . . . . . . . . . . .
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3. Practical implementation of an aerosol random laser 3.1 Experimental setup and characterization of the amplifying aerosol . . 3.2 Coherent random lasing from the polydisperse droplet array . . . . . 3.2.1 Longitudinal and transverse emission spectra . . . . . . . . . . 3.2.2 Spectral image, threshold and frequency fluctuations . . . . . 3.3 Emission properties of a dye-scatterer random laser in a microchannel
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4. A monodisperse aerosol random laser 4.1 Generation of monodisperse amplifying aerosol . . . . 4.2 Whispering gallery modes for characterization . . . . 4.3 Collective lasing from the monodisperse microdroplet 4.3.1 Discretization of frequency distribution . . . . 4.4 Characteristics of the collective modes . . . . . . . . 4.4.1 Threshold behavior . . . . . . . . . . . . . . . 4.4.2 Angular distribution of the collective emission 4.4.3 Polarization anisotropy . . . . . . . . . . . . .
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5. Lasing from a quasi-one-dimensional, amplifying period-on-average . . . 5.1 The transfer matrix method . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 Scattering and phase matrices . . . . . . . . . . . . . . . . . . . . . 5.1.2 A single dielectric layer . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3
