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University Microfilms International 300 North Zeeb Road Ann Arbor, Michigan 48106 USA St, John's Road, Tyler's Green High Wycombe. Bucks, England HP10 8HR 78-5888 McMANAMON, Paul Francis, 1946- AN INVESTIGATION OF FLASHLAMP PUMPED DYE LASERS. The Ohio State University, Ph.D., 1977 Physics, optics University Microfilms International, Ann Arbor, Michigan 48106 @ 1977 PAUL FRANCIS McMANAMON ALL RIGHTS RESERVED AN INVESTIGATION OF FLASHLAMP PUMPED DYE LASERS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Paul Francis McManamon, B.S., M.S. ***** The Ohio State University 1977 Reading Committee: Approved By Prof. Clifford V. Heer Prof. K. Narahari Rao Prof. Frederick P. Dickey Adviser Department of Physics VITA July 1, 1946 Born - Cleveland, Ohio 1968 . B.S. Physics, John Carroll University, Cleveland, Ohio 1968-1970 . Physicist, Electronic Warfare Wright-Patterson AFB, Dayton, Ohio 1970-1972 . Electronics Engineer, Electronic Warfare Wright-Patterson AFB, Dayton, Ohio 1973 . M.S. Physics, The Ohio State University Columbus, Ohio 1973-1976 . Electronics Engineer, Avionics Engineering Wright-Patterson AFB, Dayton, Ohio 1976-1977 . Electronics Engineer, Laser Development Wright-Patterson AFB, Dayton, Ohio PUBLICATIONS "Wavefront Correction with Photon Echoes," Optics Communications, to be published, by Prof. Clifford V. Heer and Paul F. McManamon. "Analysis of Candidate Electro-Optical Countermeasure Systems." Twenty-First Annual Joint Electronic Warfare Planning Conference, May, 1976. "Homing Accuracy Requirements for Deployment of Expendable Jammers (U)." August, 1970, ASD-TR-70-12. In addition twenty-one technical memorandums on various subjects have been written. FIELDS OF STUDY Major Field: Physics Studies in Laser Physics. Professor Clifford V. Heer ii TABLE OF CONTENTS Page VITA ............................................................ ii LIST OF TABLES .......................................'.......... v LIST OF FIGURES................................................. vii Chapter I. INTRODUCTION ......................................... 1 II. THE IDEAL DYE L A S E R ................................ 3 A; Rate Equation Development........................... 3 B. Dye Characteristics........................... 9 C." A Simplified Set of Rate Equations ........ 12 D. A CW Solution of the Rate Equations......... 14 E. A Digital Solution of the Transient Rate Equations ............................. 23 III. THE COMMERCIAL FLASHLAMF PUMPED DYE LASER.......... 26 A. Introduction ................................. 26 B. The Coaxial Flashlamp......................... 26 1. Blackbody Temperature..................... 28 2. Distribution of Absorbed Pump Photon Density ......................... 31 3. Distribution of Local Heating............ 37 4. Shockwave Effects......................... 41 C. Beam Divergence............................... 48 D. Steady State Optical Distortion Due to the Dye M e d i u m .................................. 52 1. Distortion of a Transmitted HeNe Beam. 52 2. Auto-Collimator Results.................. 57 3. Twyman Green Results ..................... 58 4. Light Focusing Experiments .............. 62 E. Discussion of the Laser Pulse Shape........ 65 iii TABLE OF CONTENTS (continued) Chapter Page IV POTENTIAL IMPROVEMENTS ............................... 81 A. Resonator Considerations ....................... 81 1. Introduction ............................... 81 2. A Discussion of the Influence of Optical Distortion on Resonator Q ................ 83 3. Beam Divergence Measurement Theory .... 89 4. A Discussion of Candidate Resonators . 95 5. Beam Divergence Measurements .............. 102 6 . Cavity Loss Measurements .....................107 B. Use of Triplet Quenchers ...............118 C. Cavity Dumping ..................................... 1^9 1. Switching Mechanisms ...................... 129 2. Experimental Results ...................... 1^8 3. Anticipated Optimal Configuration............151 D. Q Switching a Dye Laser.............. 155 E. Alternate Dye Cell Configurations.................162 F. Double Laser Configurations....................... 168 V CONCLUSIONS................................................ 174 APPENDICES A The DY2 Computer Program ............................. 177 B PUMP Computer Program.....................................182 C BOUNCE Computer Program .............................. 188 D Selection of an Electro-Optical Crystal for S w i t c h i n g ............................................... 195 BIBLIOGRAPHY ...................................................... 214 iv LIST OF TABLES Page 1 Simple Cross Section Values ........................... 12 2 Values of 1/A and A, Found in the Literature . 18 ca be 3 FT/Fn vs and J ......................................... 22 J u 4 Commercial Flashlamp Pumped Dye Laser ................ 27 5 Blackbody Temperature of a Coaxial Lamp .............. 30 6 Average Number of Photons Per Mode 31 7 Pump F l u x .................................................. 31 8 E vs r for C = 10 ^ Molar RD6 G ......................... 40 P 9 Percent Volume Reached by Pressure Wave from Light Absorbed at the Dye Boundary ............................41 10 Transmission Through a Pinhole............................64 11 Parameters of a Flashlamp Pumped Dye Laser.............. 6 6 12 The Exponential Gain Region .............................. 6 8 13 Energy per Pulse vs Concentration .................... 6 8 14 Output Energy with 85% T Mirror ..........................74 15 Percent Loss vs Average Distortion....................... 8 8 16 Characteristics of the Fundamental Mode of Various Resonators................................................. 100 17 "Half Confocal" Resonator Performance ........... 106 18 The Effect of a Variable Aperture . ............. 115 19 Allowed Configurations....................................131 20 FTIR Crystal Separation for a Given Reflection. 134 21 FTIR Switching Performance............................... 135 v LIST OF TABLES (continued) Page 22 Cavity Loss Mechanisms ...................... 151 23 Stored Energy...................................... .. 160 24 Initial Gain Per Pass vs Concentration ........... 161 25 Liquid Considered to Fill Diffuse Reflecting Cell. 166 26 A Partial List of PUMP Variables .................. 182 27 A Listing of the PUMP Program...................... 183 -4 28 PUMP Output for C = 10 M ........................ 184 29 PUMP Output for C = 5 x 10 ^ M .................... 185 30 PUMP Output for C = 2.5 x 10~ 5 M .................. 186 -5 31 PUMP Output for C = 10 M ........................ 187 32 A Listing of the BOUNCE Computer Program ......... 190 33 Sample Output of the BOUNCE Program................ 192 34 Summary of BOUNCE Computer Runs.................... 194 35 Candidate E-0 Modulator Crystals .................. 196 vi LIST OF FIGURES Figure Page 1 Energy Level Diagram................................... 4 2 Rodamine 6 G in Ethanol................................ 10 3 Rodamine 6 G in Water'................................... 11 4 Computer Generated Plot .............................. 25 5 Projection onto the Base of the Cylinder.............. 33 6 Full View of the Coaxial Geometry ................... 33 7 ,Densitometer Traces .................................. 35 8 Pump Absorption Profiles.............................. 36 9 Laser Set-up............................................ 43 10 Pulse Shape Results with Off-center Apertures . 45 11 Experimental Set-up ............. ;.................. 46 12 Transmission