Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 58, Number 12
Friday–Saturday, October 18–19, 2013; Denver, Colorado
Session D1: AMO II: Nonlinear Laser Propagation |
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Chair: Chip Durfee, Colorado School of Mines Room: 151 |
Friday, October 18, 2013 2:00PM - 2:24PM |
D1.00001: Nonlinear laser propagation Invited Speaker: Jerry Moloney |
Friday, October 18, 2013 2:24PM - 2:48PM |
D1.00002: Modification of intense light by propagating in air Invited Speaker: Ladan Arissian In thriving to reach higher intensities, amplified light pulses are compressed in time and space. Although rigorous methods are used to characterize the spatio-temporal properties of a pulse at the output of a laser system, the fields at the focal point cannot be directly measured. We show in this paper the nonlinear effect on intense laser pulses propagating in air, prior to reaching a focus or forming a filament, a state of light where nonlinear Kerr focusing balances a plasma induced defocusing. It is accepted that in laser filaments the peak intensity of light is determined by intensity clamping. In order to understand the microscopic interaction of light and matter in the propagation of ultrashort pulses in air, we monitor the fluorescence of nitrogen at 337 and analyze the state of polarization for various pulse energies and pulse widths. In order to separate the effect of light preparation (the focusing phase) from the interaction at focus, for all cases of study we compare the measurements of preparation in air with focusing in vacuum. A long tube (3 meters) is maintained at 1 torr pressure and connected to atmospheric air with an aerodynamic window. We show that elliptical polarization is not preserved in filament formation. The molecular orientation induces cross-phase modulation resulting in stronger self-focusing of the weaker polarization.\\[4pt] In collaboration with Shermineh Rostami, Brian Kamer, and Jean Claude Diels, University of New Mexico. [Preview Abstract] |
Friday, October 18, 2013 2:48PM - 3:00PM |
D1.00003: Broadband shearing interferometer for divergence characterization Amanda Meier, Charles Durfee Collimation testing for ultrafast pulses is important for grating compressor alignment, astigmatism correction and for the new technique of simultaneous spatial and temporal focusing (SSTF). Traditional techniques for checking collimation include knife-edge and camera scans, as well as shearing plate interferometry. The latter approach does not work well for broadband pulses because intrinsic relative time delays are larger than the coherence time. We have developed a novel polarized Sagnac shearing interferometer which combines spatial and spectral interference. We use birefringence to introduce a relative time delay to give reference spectral fringes. Divergence and spatial shear results in a local angle between the beams. The combination gives fringes in the spatial-spectral domain that rotate with divergence. We will present our experimental setup and fringe analysis techniques, along with estimates of the sensitivity of our measurement. In addition to collimation and astigmatism testing, we propose an extension to characterize angular spatial chirp. [Preview Abstract] |
Friday, October 18, 2013 3:00PM - 3:12PM |
D1.00004: In situ characterization of SSTF beams yielding phase and M2 Micahel Greco, Amanda Meier, Erica Block, Jeff Squire, Charles Durfee Simultaneously spatial and temporal focusing (SSTF) of large bandwidth, femtosecond pulses has been demonstrated as a useful way to deliver high energy, ultrafast pulses to a focal plane without incurring second order effects that would damage material or distort the beam as it propagates. Though the optical components used to create these beams are common, the alignment of them (gratings and focusing optics in particular) is difficult. By combining information from a knife edge scan and a dispersion scan we can correct for misalignment in a grating compressor. Similar technicians for determining phase information of a conventionally focused ultrafast laser pulse involve spatial light modulators (SLM) to impart spectral phase[1]. An SSTF beam will experience a change in second order phase away from the focal plane along the axis of propagation. This may be used in lieu of an SLM for the purpose of observing higher order phase with a dispersion scan. [Preview Abstract] |
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