Ultrafast Beam Filamentation - Spatio-temporal Characterization and Control

200 word) In this project, we studied the linear and nonlinear propagation of structured beams of ultrafast pulses. We have been taking advantage of the special characteristics of spatially-chirped beams, in which the frequency components cross each other at the focus of a lens. In this configuration, the pulse focuses temporally and spatially at the same time. We developed a theory for understanding the beam propagation, verified aspects of this theory experimentally, developed a suite of diagnostics to test the alignment of these beams. We also demonstrated application of these beams to cutting biological material. In the project we investigated the spatio-temporal properties of cross-polarized wave generation and its application to pulse characterization. We developed a four-wave mixing apparatus in which the spatial chirp and pulse front is controlled. We extended our knowledge of beam propagation to Bessel-Gauss beams, and developed a technique to produce a uniform axial line focus by shaping only the spatial phase of the starting beam. Finally, we showed for the first time that Kerr-lens modelocking can be achieved in a Ti:sapphire oscillator pumped only by laser diodes. Executive summary of results: 1. SSTF theory: Intuitive Analysis of Space-time Focusing with Double-ABCD Calculation • We developed an analytic and intuitive approach to calculate the spatio-temporal propagation of wide bandwidth pulses that have spatial chirp. In this approach, each frequency component can be propagate through an optical system using Gaussian ABCD matrices, while the central beam axes of the components is traced through the system with geometric optics. The technique provides useful insight into how space-time focusing occurs as well as how these beams can be controlled to control spatio-temporal propagation. • In collaboration with Ya Cheng at the State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, we showed experimentally and theoretically that the peak intensity distribution for a focused spatially chirped pulse is tilted. This new tilt is qualitatively distinct from the pulse front tilt. • Method is described in detail in a 16 page paper (Optics Express, 2012) and in an invited book chapter (Nova Science, 2013). A talk contributed to CLEO 2012 was one of a small number of talks that was upgraded to an invited talk. 2. SSTF experiment: Highly Localized Plasma Formation in Air Using Space-time Focusing of mJ Ultrafast Pulses • We developed a high-power spatial-chirp focusing experiment and demonstrated that a beam with 5 times the critical power for self-focusing can propagate to a focal point without distortion. • Presented at CLEO, Advanced Photonics and a local conference. 3. SSTF application: Tissue ablation • Demonstrated extreme localization of tissue cutting using SSTF, with a porcine eye lens as the target. SSTF showed much more precise cutting and lower collateral damage than a conventional focus. • Paper in Biomedical Optics Express (2013). Presented at Photonics West and in an invited talk in Corsica, France (2013). 4. SSTF characterization: Passive dispersion scan, Broadband beamlet scan, and Broadband shearing interferometry • We have developed three techniques to characterize broadband, spatially-chirped beams. All three of these have been demonstrated experimentally, and we are in the process of finalizing the analysis for publication. • The passive dispersion scan takes advantage of the geometric spectral phase that results from an angular spatial chirp predicted by our theory. The spectrum of the second harmonic is monitored as the doubling crystal is moved along the optical axis. This movement effectively changes the second order phase on the pulse, producing an image that traces out the second derivative of the spectral phase intrinsic to the pulse. • The broadband beamlet scan is a spectrally resolved knife-edge scan, that will give the beamlet axis direction, the location of the waist, and the size of the waist. Since all spectral components of the spatially-chirped beam are scanned at once, this measurement gives the complete description of the spatial characteristics of the spatially-chirped beam. • Broadband shearing interferometry uses a Sagnac interferometer to produce a spatial shear (transverse displacement) and a birefringent plate to give a time delay. The resulting interferogram in an imaging spectrometer yields a measurement of the divergence angle as a function of frequency. We are working to extend this technique to make a self-referenced spatial wavefront measurement and a measurement to characterize angular spatial chirp. 5. Characterization: Development of a passively stable interferometric transient grating apparatus to characterize nonlinear dynamics • With an aim towards developing plasma diagnostics our MS student developed a passively stable optical arrangement for interferometric transient grating measurements. • Presented at two local conferences. 6. Pulse characterization and energy contrast measurement using crossed-polarized wave generation (XPW) and self-referenced spectral interferometry • We developed a method to use XPW and spectral interferometry to quantify the energy contrast of laser pulses, an important issue in spectral interferometry and any experiments with linear pulse interactions. • Presented at CLEO 2011, manuscript in preparation. 7. Efficiency enhancement of crossed-polarized wave conversion of low energy pulses via imaged double-pass • We showed that the spatio-spectral phase of cross-polarized wave (XPW) generated light can be controlled through re-imaging so as to improve double-pass XPW conversion. This will have applications to pulse shortening and contrast cleaning, especially for pulses from fiber amplifiers which are known for developing nonlinear distortion. • Presented at CLEO 2012, manuscript in preparation. 8. Pulse delivery to a uniform line focus with shaped Bessel-Gauss beams • We developed a technique to shape the spatial phase of a Bessel-Gauss ring beam to produce an on-axis line focus with a desired intensity profile. This was a collaboration with J. Gemmer and J. Moloney at U. Arizona. • Two papers in 2013 (one still in review) 9. Direct Diode Pumped Kerr Lens Modelocked Ti:Sapphire Laser Oscillator • We developed the first Kerr Lens modelocked Ti:sapphire laser that is directly pumped by laser diodes. We employed two blue laser diodes (450nm), focused into a modified Ti:sapphire laser. • Published in Optics Express and featured on the cover of Laser Focus World. Presented at CLEO 2012, Ultrafast Phenomena 2012, Frontiers in Optics 2012. Students supported: Marin Iliev (PhD, anticipated graduation Spring 2014) Michael Greco (PhD, anticipated graduation, Spring 2015) Benjamin Galloway (MS, graduated Spring 2012, now a PhD student in the Kapteyn/Murnane group at U. Colorado). Honors: In 2013, C. Durfee was elected as a Fellow of the Optical Society of America Invited talks and seminars: J. Squier, E. Block, M. Greco, A. Allende Motz, C. Durfee, O. Masihzadeh, D. Ammar, M. Kahook, N. Mandava, “Simultaneous spatio-temporal focusing for tissue manipulation, “ invited talk, Progress in Ultrafast Laser Modifications of Materials, Cargese, Corsica, April 14-19, 2013. C. Durfee, M. Greco, A. Meier, E. Block, J. Squier,” Spatial chirp control of high intensity 4D pulse focusing for laser-matter interactions,” invited talk, Progress in Ultrafast Laser Modifications of Materials, Cargese, Corsica, April 14-19, 2013. J. Squier, “Inexpensive femtosecond laser sources and precise targeted ablation using simultaneous spatial and temporal focusing, “ invited talk, Frontiers and Challenges in LaserBased Biological Microscopy, Telluride, CO, August 5-9, 2013. C. G. Durfee, J. A. Squier, M. Greco, B. Galloway, A. Meier, E. Block, “Control of ultrafast laser-matter interactions with 4D pulse focusing,” invited talk Physics of Quantum Electronics (PQE), Snowbird, UT (Jan 2013). “Linear and Nonlinear Dynamics of Focusing Spatially-Chirped Ultrafast Pulses,” Michael Greco, Amanda Meier, Erica Block, Dawn Vitek and Jeff A. Squier, invited talk COFIL, Tuscon, AZ (2012). J. Squier, “Multifocal multiphoton imaging and micromachining with spatial and temporal focusing, “ invited talk 8845-3, SPIE Optical Engineering and Applications, San Diego, CA, Durfee, C., Squier, J. A., Meier, A., Iliev, M., Greco, M., Block, E., & Vitek, D. N. Characterizing and controlling the spatial and temporal evolution of ultrafast laser pulses. Seminar, University of Colorado. Boulder, Colorado (March, 2012). Durfee, C., Greco, M., Block, E., Vitek, D. N., & Squier, J. A., “Intuitive analysis of space-time focusing with double ABCD calculation,” contributed upgraded to invited talk, Conference on Lasers and Electro-Optics (CLEO). San Jose, CA (May 8, 2012). Jeff Squier, Dawn Vitek, Erica Block, Michael Young, Charles Durfee, "Femtosecond micromachining using spatio-temporal focusing," invited talk, Optomechatronics Conference, Hong Kong, China, November 1-3, 2011 Jeff Squier, Dawn Vitek, Erica Block, Michael Young, Charles Durfee, "Femtosecond micromachining using spatio-temporal focusing," invited talk, Ultrafast Optics Conference, Monterey, CA, Sept. 26-30, 2011 Contributed talks and posters: “Ultrafast dynamics of 4D focusing of spatially-chirped pulses,” C. G. Durfee, M. Greco, E. Block, J. A. Squier. Ultrafast Optics, Davos Switzerland (March 2013). “Passively aligned four-wave mixing apparatus for investigating high-intensity laser-matter interactions”, A. Meier, M. Greco, J. Thomas, J. A. Squier, C. G. Durfee. Photonics West (Feb 2013). "Highly localized plasma formation in air using space-time focusing of mJ ultrafast pulses," M. Greco, J. A. Squier, C.G. Durfee, at Conference on Earth Energy Research (Golden, March 2012). "Passively stable and dispersion compensated transient grating apparatus to measure ultrafast dynamics," B. Galloway, C.G. Durfee, at Colorado School of Mines colloquium (Golden, April 2012). “Two photon microscope based on direct diode pumped Ti:sapphire laser,” Jeff A. Squier, Michael Young, Tristan Storz, Jonathan Garlick, Steven Hill, Matt Kirchner, Greg Taft, Kevin Shea, Henry Kapteyn, Margaret Murnane, Charles Durfee III, and Sterling Backus, Ultrafast Phenomena, Geneva, Switzerland, July 2012. “Kerr-Lens Modelocked Ti:Sapphire Laser Oscillator Directly Pumped with Blue Diodes,” Charles G. Durfee, Tristan Storz, Jonathan Garlick, Steven Hill, Jeff A. Squier, Matt Kirchner, Greg Taft, Kevin Shea, Henry Kapteyn, Margaret Murnane, and Sterling Backus, Frontiers in Optics, Rochester, NY (2012). C. G. Durfee, T. Storz, J. Garlick, S. Hill, J. A. Squier, M. Kirchner, G. Taft, K. Shea, H. Kapteyn, M. Murnane, and S. Backus, “Direct diode pumped Kerr lens modelocked Ti:Sapphire laser oscillator,” CM2J, 1–2 Conference on Lasers and Electro-Optics (CLEO) (2012). Greco, M., Meier, A., Block, E., Vitek, D. N., Squier, J. A., & Durfee, C. G., Highly localized plasma formation in air using space-time focusing of mJ ultrafast pulses. Advanced Solid State Photonics. Colorado Springs, CO (June 17, 2012). Galloway, B., & Durfee, C. G., Passively stable and dispersion compensated transient grating apparatus to measure ultrafast dynamics. Optical Society of America, Rocky Mountain Section. Boulder, CO (2012, April 19). M. Greco, A. K. Meier, E. Block, M. Iliev, D. N. Vitek, J. A. Squier, C. G. Durfee, “Highly localized plasma formation in air using space-time focusing of mJ ultrafast pulses,” JW4A, 1–2 Conference on Lasers and Electro-Optics (CLEO) (2012). M. Iliev, A. K. Meier, C. G. Durfee, “Improvement of double-pass crossed-polarized wave efficiency and beam quality via imaging,” JTh2A, 1–2 Conference on Lasers and Electro-Optics (CLEO) (2012). "Measurement of Energy Contrast of Amplified Ultrashort Pulses using Cross Polarized Wave Generation and Spectral Interferometry," M. Iliev, A. K. Meier, D. E. Adams, J. A. Squier, and C. G. Durfee, in CLEO:2011 Laser Applications to Photonic Applications, OSA Technical Digest (CD) (Optical Society of America, 2011), paper CTuO2. “Spatio-temporally Focused Femtosecond Laser Pulses for Anisotropic Writing in Optically Transparent Materials,” D. N. Vitek, Erica Block, Yves Bellouard, Daniel E. Adams, Sterling Backus, David Kleinfeld, Charles G. Durfee, and Jeff A. Squier. Conference on Lasers and Electro-Optics (CLEO), OSA Technical Digest (CD) (Optical Society of America, 2011), paper CWO5. Refereed journal articles: C.G. Durfee, T. Storz, J. Garlick, S. Hill, J. A. Squier, M. Kirchner, G. Taft, K. Shea, H. Kapteyn, M. Murnane, and S. Backus, “Direct diode-pumped Kerr-lens mode-locked laser”, Opt Express, 20, 13677 (2012). Durfee, C. G., Greco, M., Block, E., Vitek, D., & Squier, J. A. “Intuitive analysis of space-time focusing with double-ABCD calculation.” Optics Express, 20, 14244 (2012). Benjamin Galloway, “Development of a passively stable and dispersion compensated transient grating apparatus to measure ultrafast dynamics” M.S. Thesis, Applied Physics, Colorado School of Mines, May 2012. Charles G. Durfee, Michael Greco, Erica Block, Dawn Vitek, and Jeff A. Squier, “Intuitive Analysis Of Ultrafast Pulse Propagation Through Angularly Dispersive Structures,” invited book chapter New Developments in Photon and Materials Research, ed. J. I. Jang (NOVA