University of New Mexico UNM Digital Repository Optical Science and Engineering ETDs Engineering ETDs 6-26-2015 Pulsed laser induced breakdown in solid state materials and air Zhanliang Sun Follow this and additional works at: https://digitalrepository.unm.edu/ose_etds Recommended Citation Sun, Zhanliang. "Pulsed laser induced breakdown in solid state materials and air." (2015). https://digitalrepository.unm.edu/ ose_etds/41 This Dissertation is brought to you for free and open access by the Engineering ETDs at UNM Digital Repository. It has been accepted for inclusion in Optical Science and Engineering ETDs by an authorized administrator of UNM Digital Repository. For more information, please contact [email protected]. Z ¡ ¢£¤¡ ¢¥ ¦§¢ Candidate Optical Science and Engineering - Physics Department This dissertation is approved, and it is acceptable in quality and form for publication: Approved by the Dissertation Committee: Wolfgang Rudolph, Chair Francisco Elohim Becerra Chavez Paul Schwoebel David Cremers i P¨© © ¨ in solid state materials and air by Zhanliang Sun B.S., Applied Physics, Harbin University of Sci. & Technology, 2002 M.S., Optics, Tsinghua University, 2006 M.S., Optical Sci. & Engineering, University of New Mexico, 2010 DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Optical Science and Engineering The University of New Mexico Albuquerque, New Mexico May, 2015 ii c 2015, Zhanliang Sun iii D To my Lord, Christ Jesus, for His encouragement and comfort. No discipline seems pleasant at the time, but painful. Later on, however, it produces a harvest of righteousness and peace for those who have been trained by it. – Hebrews 12: 11 Let us not become weary in doing good, for at the proper time we will reap a harvest if we do not give up. – Galatians 6: 9 iv A !"# I would like to thank my advisor, Professor Wolfgang Rudolph, for his support, guidance and patience. I am thankful to my dissertation committee members: Dr. Francisco Elohim Becerra Chavez, Dr. Paul Schwoebel and Dr. David Cremers. I would also like to thank Dr. Luke Emmert, who kindly support me through this journey. Many thanks to Dr. Jinhai Chen and Dr. Zhenwei Wang. From them, I learned a lot of experimental skills. I want to thank Prof. Detlev Ristau (Laser Zentrum Hannover e.V., Hannover, Germany) and Prof. Carmen S. Menoni (Colorado State University, Fort Collins, CO, USA) and their respective groups for the high-quality samples. Many thanks to our research projects collaborators, Dr. David Cremers (Applied Research Associates, Inc. Albuquerque, NM, USA) and Dr. Matthias Lenzner (Lenzner Research LLC, Tucson, AZ, USA). Thanks to the rest of our group for helpful discussion: Vasudevan Nampoothiri, Mark Mero, Duy Nguyen, Reed Weber, Cristina Rodriguez, Xuerong Zhang, Ben Oliker, Behshad Roshanzadeh, Yejia Xu, Ahmad Mansoori. I am grateful for my wife, Lucy Cheng, for her support. Also, gratitude to my parents, for their encouragement for my graduate study abroad. v P¨© © ¨ in solid state materials and air by Zhanliang Sun B.S., Applied Physics, Harbin University of Sci. & Technology, 2002 M.S., Optics, Tsinghua University, 2006 M.S., Optical Sci. & Engineering, University of New Mexico, 2010 Ph.D., Optical Sci. & Engineering, University of New Mexico, 2015 Abstract Laser induced breakdown is important in applications ranging from laser machin- ing to laser induced breakdown spectroscopy to laser induced damage. Laser induced breakdown in dielectric materials results from a combination of multiphoton absorption (MPA), tunneling and avalanche ionization. Aspects of these processes have been studied through measurements of the laser induced dam- age threshold (LIDT) and its dependence on pulse duration, polarization and wave- length. At long pulse durations ( > 1 ns), relaxation of conduction band electrons during the pulse is responsible for the increased LIDT compared to scaling derived from sub-picosecond pulses. Linear polarization produces lower LIDT than circular polarization for MPA order of m = 3 and 4 with femtosecond and picosecond pulses. Laser damage tests with two-color pulse pairs show that the damage threshold de- pends on the order of the pulse pair. The measured difference between single-pulse vi a $% &'()*+(,- + '(., /01 2 3 . a ++4*5, a $% 3 '., % . *(* a 2 ,6 *,$). 7a. , 8 +(a *$,% 7* )4 c c c the creation of laser induced defects. Measurements of damage and ablation thresholds of dielectrics and metals for dif- ferent numbers of pulses show the effect of laser induced material modifications, also called material incubation. A phenomenological incubation model based on changes of (i) absorption coefficient and (ii) critical energy is introduced and successfully ex- plained the dependence of the ablation threshold on the number of pulses for metals and dielectrics. We explore LIDTs of bulk metals using the plasma emission method. Nickel alloy shows good agreement between the crater size method and the plasma emission method. The transient electron temperature in a femtosecond air plasma (filament) was determined from absorption and optical diffraction experiments. The electron tem- perature and plasma density decay on similar time scales of a few hundred picosec- onds. Comparison with plasma theory reveals the importance of inelastic collisions that lead to energy transfer to vibrational degrees of freedom of air molecules during the plasma cooling. vii # C List of Figures xiv List of Tables xxi Glossary xxiii 1 Introduction 1 1.1 Researchbackgroundandmotivation . 1 1.2 Openquestions .............................. 5 1.2.1 Interactionoflaserpulseswithsolids . 5 1.2.2 Interaction of laser pulses with gaseous media . 9 1.3 Dissertationoutline............................ 10 2 Experimental tools and techniques 11 2.1 Lasersystem ............................... 11 2.1.1 Femtosecondoscillatorandamplifier . 11 viii 9 : ;<= ;<> 2.1.2 Thirdharmonicgenerator . 13 2.2 Dataacquisitionsystem . 14 2.3 Pulsedurationmeasurement . 17 2.4 Beamsizemeasurement . 17 3 Material modifications by laser pulses and optical damage 19 3.1 Introduction................................ 19 3.1.1 Background ............................ 19 3.1.2 Chaptergoalsandcontents . 22 3.2 PulsedLIDmodel............................. 23 3.2.1 Electrondensityrateequations . 23 3.2.2 Damagecriterion . 25 3.2.3 Incubationinmultiplepulsedamage . 25 3.3 LIDtestwithnspulsesandmodeling . 27 3.3.1 Introduction............................ 27 3.3.2 Experimentalsetup. 28 3.3.3 Results............................... 31 3.3.4 LIDTmodeling .......................... 33 3.4 Damagemeasurementswithapulsepair . 37 3.4.1 Experimentalsetup. 37 3.4.2 Results............................... 39 ix 9 : ;<= ;<> 3.5 MPA measurements on thin dielectric substrates . .... 40 3.5.1 Introduction............................ 40 3.5.2 Experimentalsetup. 42 3.5.3 MPAresults............................ 43 3.6 Two-colorpulsepairdamagetest . 51 3.6.1 Introduction............................ 51 3.6.2 Experimentalsetup. 52 3.6.3 Results............................... 56 3.7 LID test with different input beam polarization . .... 59 3.7.1 Introduction............................ 59 3.7.2 Experimentalsetup. 60 3.7.3 Damage threshold dependence on polarization . 62 3.8 LID characterization through crater morphology . ...... 65 3.8.1 Introduction............................ 65 3.8.2 Crater morphology dependence on polarization . ... 68 3.8.3 Damage process revealed from crater morphology . 69 3.9 Chaptersummary............................. 74 4 Empirical incubation law for laser damage and ablation thresholds 76 4.1 Introduction................................ 76 4.1.1 Literaturereviewandopenquestions . 76 x 9 : ;<= ;<> 4.1.2 Chaptergoals ........................... 81 4.2 Using crater size and scattering change methods to measure LIDTs of dielectricfilms............................... 82 4.2.1 Experimentalsetup. 82 4.2.2 Results............................... 83 4.3 Using crater size method to measure LIDTs on bulk metals and metal films .................................... 86 4.3.1 Experimentalsetup. 86 4.3.2 Ablatedareacharacterization . 88 4.3.3 Results............................... 89 4.4 Measurement of the ablation threshold using plasma emission .... 93 4.4.1 Setup ............................... 93 4.4.2 Results............................... 96 4.5 Modelforincubation . 99 4.5.1 Multiple-pulse laser induced damage threshold . 100 4.5.2 Incubationmodel . 102 4.5.3 Fittingofexperimentaldata . 105 4.6 Chaptersummary............................. 109 5 Femtosecond laser induced filament in air 111 5.1 Introduction................................ 111 xi 9 : ;<= ;<> 5.1.1 Literaturereviewandopenquestions . 111 5.1.2 Chaptergoals ........................... 113 5.2 Transient absorption and diffraction of an air plasma . 114 5.3 Determination of the initial plasma density and electron temperature 121 5.4 Modelinganddiscussion . 123 5.5 Waveguidingusingonefilament. 129 5.5.1 Backscatteringthroughafilament . 129 5.5.2 Field-freealignmentofmolecules . 131 5.6 Waveguidingwithmultiplefilaments . 133 5.7 Chaptersummary............................. 136 6 Summary and outlook 138 6.1 Summary ................................. 138 6.2 Outlookforfuturework . 139 A Transformations for a Gaussian pulse 142 B List of tested films 144 C Locate sample position 145 D Spatial and temporal overlap procedures 147 E Optimized film thickness for two-color damage test 151 xii 9 : ;<= ;<> F Ripples