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Nonlinear Systems for Frequency Conversion from Ir to Rf

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Nonlinear Systems for Frequency Conversion from Ir to Rf NONLINEAR SYSTEMS FOR FREQUENCY CONVERSION FROM IR TO RF Dissertation Submitted to The School of Engineering of the UNIVERSITY OF DAYTON In Partial Fulfillment of the Requirements for The Degree of Doctor of Philosophy in Electro-Optics By Brian D. Dolasinski, M.S. UNIVERSITY OF DAYTON Dayton, OH December 2014 NONLINEAR SYSTEMS FOR FREQUENCY CONVERSION FROM IR TO RF Name: Dolasinski, Brian David APPROVED BY: ___________________ ___________________ Joseph W. Haus, Ph.D. Partha Banerjee, Ph.D. Advisory Committee Committee Member Chairman Director Associate Professor Electro-Optics Electro-Optics Program Program ___________________ ___________________ Imad Agha, Ph.D. Adam Cooney, Ph.D. Committee Member Committee Member Assistant Professor Research Physicist Physics Program AFRL ___________________ ___________________ John G. Weber, Ph.D. Eddy M. Rojas, Ph.D., M.A., P.E. Associate Dean Dean School of Engineering School of Engineering ii ABSTRACT NONLINEAR SYSTEMS FOR CONVERSION FROM IR TO RF Name: Dolasinski, Brian David University of Dayton Advisor: Dr. Joseph W. Haus The objective of this dissertation is to evaluate and develop novel sources for tunable narrowband IR generation, tunable narrowband THz generation, and ultra- wideband RF generation to be used in possible non-destructive evaluation systems. Initially a periodically poled Lithium Niobate (PPLN) based optical parametric amplifier (OPA) is designed using a double-pass configuration where a small part of the pump is used on the first pass to generate a signal, which is reflected and filtered by an off- axis etalon. The portion of the pump that is not phase matched on the first pass is retro- reflected back into the PPLN crystal and is co-aligned with the narrow bandwidth filtered signal and amplified. We demonstrate that the system is tunable in the 1.4 μm -1.6 μm signal range with a linewidth of 5.4 GHz. Next the outputs of seeded, dual periodically poled lithium niobate (PPLN) optical parametric amplifiers (OPA) are combined in the nonlinear crystal 4-dimthylamino-N- methyl-4-stilbazolium-tosylate (DAST) to produce a widely tunable narrowband THz source via difference frequency generation (DFG). We have demonstrated that this novel iii configuration enables the system to be seamlessly tuned, without mode-hops, from 1.2 THz to 26.3 THz with a minimum bandwidth of 3.1 GHz. The bandwidth of the source was measured by using the THz transmission spectrum of water vapor lines over a 3-meter path length. By selecting of the DFG pump wavelength to be at 1380 nm and the signal wavelength to tune over a range from 1380 nm to 1570 nm, we produced several maxima in the output THz spectrum that was dependent on the phase matching ability of the DAST crystal and the efficiency of our pyro-electric detector. Due to the effects of dispersive phase matching, filter absorption of the THz waves, and two-photon absorption multiple band gaps in the overall spectrum occur and are discussed. Employing the dual generator scheme, we have obtained THz images at several locations in the spectrum using an infrared camera that runs at a rate of 35 frames per second. We have demonstrated the ability to image 2 THz to 26 THz both in static and in real time conditions. We will present images of carbon fibers illuminated at different THz frequencies. Lastly, microwave generation was demonstrated by ultrafast photo-excitation experiments to induce non-equilibrium quasi-particle relaxation. Using a laser with a pulse energy of 1 mJ and a pulse duration greater than 120 fs (808 nm wavelength) incident on a charged, superconducting YBa2Cu2O7−δ (YBCO) thin film ring, the photo-response was measured with a series of microwave antennas. From the observed nanosecond response time of the transient pulse, we extracted the frequency spectrum in the GHz regime that was dependent on the incident beam diameter, pulse duration, power, and the physical structure of the YBCO thin film. iv ACKNOWLEDGMENTS I would like to acknowledge my former advisor, Professor Peter Powers. I will be forever thankful for his guidance, encouragement, and positive attitude during my study in the University of Dayton. He was one of my best role models for a scientist, mentor, and friend. Peter was the reason I have decided to pursue a career in nonlinear optics. I am also very grateful to my other advisor Professor Joseph Haus for his support and guidance over the course of my research with LOCI. I also wish to thank Dr. Banerjee, Dr. Agha, and Dr. Cooney for serving on my doctoral committee and their helpful insights. I would like to thank Dr. Jason Deibal and Doug Petkie at Wright State University for their assistance in THz imaging. Also a special thanks to Dr. Tim Haugen and Dr. Tom Bullard of AFRL for the opportunity to study microwave generation. I would also like to thank Tom Bullard, John Bulmer, and Jay Patel for their group effort contribution during several superconductor experiments. Most importantly I would like to thank my wife Heather, my Parents Dave and Mary, and my sister Lise who supported my educational pursuits. v TABLE OF CONTENTS ABSTRACT .................................................................................................................. iii ACKNOWLEDGMENTS ............................................................................................... v LIST OF FIGURES ..................................................................................................... viii LIST OF TABLES .......................................................................................................xii CHAPTER 1: INTRODUCTION AND OBJECTIVES ..............................................................................................................1 1.1 Introduction ............................................................................................ 1 1.2 Problem Statement .................................................................................. 2 1.3 Review of Related Techniques ................................................................ 5 1.3.1 Overview of Infrared Generation ..................................................... 5 1.3.2 Current THz wave techniques .......................................................... 7 1.3.3 Description of Wideband Microwave Generation ............................. 9 1.4 Motivation ............................................................................................. 11 1.5 Experimental Approach ........................................................................ 12 1.6 Dissertation Outline .............................................................................. 13 CHAPTER 2: PERIODICALLY POLED LITHIUM NIOBATE SEEDED OPTICAL PARAMETRIC AMPLIFIER ..............................................................15 2.1 Introduction .......................................................................................... 15 2.2 Nonlinear Interactions ............................................................................ 16 2.3 Overview of PPLN Injection Seed OPG/OPA ........................................ 17 2.3.1 OPA Wave Equation ...................................................................... 20 2.4 Quasi-Phase Matching (QPM) ............................................................... 24 2.5 Periodically Poled Lithium Niobate (PPLN) OPA ................................. 24 2.6 Etalon Seeded PPLN OPA ..................................................................... 29 2.6.1 Overview of off-axis Fabry-Perot etalon feedback seed ................. 29 CHAPTER 3: NARROW BANDWIDTH TUNABLE OPA .........................................................................................................36 3.1 Introduction .......................................................................................... 36 3.2 Narrow Bandwidth OPA ........................................................................ 37 3.2.1 Dual Pass OPG method .................................................................. 37 3.2.2 Experimental Setup ........................................................................ 41 3.3 Results ................................................................................................... 44 3.4 Application ............................................................................................ 48 3.5 Conclusion ............................................................................................. 51 vi CHAPTER 4: DIFFERENCE FREQUENCY GENERATION IN DAST .........................................................................................53 4.1 Introduction ........................................................................................... 53 4.2 Overview of THz Generation by DFG .................................................. 53 4.3 DFG Wave Equation Overview ............................................................. 54 4.4 DAST Properties ................................................................................... 56 4.5 DAST THz Model ................................................................................. 60 CHAPTER 5: NARROWBAND THZ DFG VIA DUAL SEEDED OPA .......................................................................................63 5.1 Introduction .......................................................................................... 63 5.2 THz DAST DFG .................................................................................... 64 5.2.1 Tandem Seeded MgO:PPLN OPAs ............................................... 64
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