Bulletin of the American Physical Society
2006 Four Corners Section of the APS Fall Meeting
Friday–Saturday, October 6–7, 2006; Logan, Utah
Session B2: Lasers, Optics, and Spectroscopy |
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Chair: William E. Evenson, Utah Valley State College Room: Eccles Conference Center Room 205/207 |
Friday, October 6, 2006 10:30AM - 10:42AM |
B2.00001: Development of a kHz-repetition rate TW ultrafast amplifier Charles Durfee, Thomas Planchon, Sudipta Bera, Jeff Field, Daniel Adams, Colby Childress, Jeff Squier We have developed a 2 stage amplifier for ultrafast that will deliver 20mJ, 20fs laser pulses at a repetition rate of 1kHz. The novel power amplifier is pumped by up to 100W from 4 pump lasers, necessitating cryogenic cooling of the amplifier crystal. In collaboration with Abbess Instruments, we have designed a liquid nitrogen cooled cryostat that gives a temperature rise of less than 2K with a 100W thermal load. We have also developed a high resolution, high efficiency, temporal pulse shaper that will be integrated in the system. We will present our results on using the third-harmonic signal from a glass slide in the focus to optimize the wavefront from a deformable mirror and to fully characterize the temporal profile of the output pulse. This system is already being used for micromachining studies. In the near future it will be used for the generation of high flux hard x-rays for imaging and ultrafast x-ray diffraction. [Preview Abstract] |
Friday, October 6, 2006 10:42AM - 10:54AM |
B2.00002: Direct Observation of Laser Filamentation in High-Order Harmonic Generation Gavin Giraud, John Painter, Nicole Brimhall, Mark Adams, Nathan Powers, Eric Christiansen, Matt Turner, Michael Ware, Justin Peatross We investigate the spatial evolution of a laser pulse used to generate high-order harmonics (orders ranging from 45-91) in a semi-infinite helium-filled gas cell. The 5 mJ, 30 fs laser pulses experience elongated focusing with two distinct waists when focused with f/125 optics in 80~torr of helium. An extended phase matching for the generation of harmonics occurs in the region between the double foci of the laser, where the laser beam changes from diverging to converging. [Preview Abstract] |
Friday, October 6, 2006 10:54AM - 11:06AM |
B2.00003: The Application of High-Order Harmonics to Extreme Ultraviolet Polarimetry Nicole Brimhall, John Painter, Matthew Turner, R. Steven Turley, Michael Ware, Justin Peatross We report on the construction of an extreme ultraviolet (EUV) polarimeter based on high-order harmonic generation for characterizing optical surfaces from 8-62 nm. High harmonics as an EUV source are advantageous in that they are polarized (linear, same as laser) and measurements of several wavelengths of light can be made simultaneously. Although not as bright as a synchrotron source, the flux of EUV light is 30,000 times that of a commonly used plasma source. We have demonstrated the feasibility of this project with a simple prototype instrument, which measured the reflectance of samples from 30 nm to 62 nm. The prototype demonstrated that sensitivity is sufficient for measuring reflectances as low as 0.5{\%}. The full instrument employs extensive scanning mobility as opposed to the fixed angle and fixed wavelength range of our earlier prototype. This project represents an authentic `work-horse' application for high-order harmonics, as opposed to merely demonstrating proof of concept. [Preview Abstract] |
Friday, October 6, 2006 11:06AM - 11:18AM |
B2.00004: Advantages of a Grazing Incidence Monochromator in the Extreme Ultraviolet Sarah Barton, R. Steven Turley One of the main goals of the BYU Thin Films group is to find optical constants for materials in the Extreme Ultraviolet. This is accomplished by taking reflection and transmission measurements. The addition of a Grazing Incidence Monochromator to our current system allows us to take reflectance measurements at wavelengths currently unavailable on the Normal Incidence Monochromator (Monarch). [Preview Abstract] |
Friday, October 6, 2006 11:18AM - 11:30AM |
B2.00005: Oxidation Effects on the Optical Constants of Heavy Metals Amy Grigg, Steve Turley Applications for high-energy and extreme ultraviolet light are increasing everywhere in today’s technological world. As a result, the need for understanding how light interacts with materials in this energy range of light is also increasing. This study examines a method for determining the optical constants of materials based on reflectance and transmission measurements, taking into account oxidation gradients of the material. The method of x-ray photoelectron spectroscopy rastering is found to be the best method for determining molecular composition gradients. [Preview Abstract] |
Friday, October 6, 2006 11:30AM - 11:42AM |
B2.00006: From Whence Come the Electrons Jonathan Abbott, J.R. Dennison, Jason Kite, R.C. Hoffmann, Rob Davies Measuring the electron emission energy spectrum from a material yields a similar curve regardless of the incident energy source, whether it is electrons, ions, photons (photoemission), or even thermal energy (thermionic emission). When measuring the spectrum for electron induced electron emission, there is a question of whether it is possible to distinguish the electrons originating from the beam from those originating inside the material. We discuss the limits of the conventional boundary of 50 eV between the electrons originating from the material (secondary electrons) and those originating from the primary beam (backscattered electrons). We present experimental results suggesting a more realistic boundary at the observed minimum in the emission spectrum.~ We also show that simple analysis of emission spectra of biased conducting samples (and charged insulating samples) can distinguish between these two populations. [Preview Abstract] |
Friday, October 6, 2006 11:42AM - 11:54AM |
B2.00007: The Emission Angle and Incident Energy Dependence of the Boundary between Secondary and Backscattered Electrons J.R. Dennison, Jason Kite A more realistic boundary to separate the electrons originating from the sample (secondary electrons) and those originating from the primary beam (backscattered electrons) in electron-induced electron emission spectra is the observed minimum in the emission spectrum. We present measurements of the emission spectra of polycrystalline Au over a range of incident energies from 100 eV $<$ E$_b$ $<$ 2500 eV, as a function of emission angle and energy, E$_b$. The dependence of the position of Emin and its associated yield intensity are investigated in terms of E$_b$ and emission angle. Emin is roughly constant at $\sim$45\% of E$_b$, but does show some more complex dependence on E$_b$. No significant emission angle dependence of E$_{min}$ is evident. The emission spectral intensity at E$_{min}$, N(E$_{min}$), decreases with increasing emission angle, and scales approximately as a Lambert law proportional to the cosine of the emission angle. Finally, we discuss the effect of choosing this more realistic value to separate secondary and backscattered electrons on the secondary and backscattered yield values. [Preview Abstract] |
Friday, October 6, 2006 11:54AM - 12:06PM |
B2.00008: Measuring Auger Signatures Using a Rotatable, High-Resolution Retarding Field Analyzer Faraday Cup Detector Jason Kite, J.R. Dennison Single event energy losses of electron scattering have been observed in the angle- and energy-resolved electron emission spectra. The surface sensitive Auger signature is commonly used to characterize sample quality and determine surface species via their emission energy signature. Auger measurements are usually accomplished with a lock-in amplifier and electrostatic analyzer or LEED-style retarding field analyzer. Our measurements confirm that Auger peaks can also be measured with a simple retarding field analyzer Faraday cup detector. Design details and sample measurements are presented. The signature Auger peaks measured on polycrystalline Au of the MNN transitions, at 1720 eV and 2030 eV, compare very well with those in the literature. Peak dependence on incident energy and emission angle are also discussed. This work is sponsored by the NASA Space Environments and Effects Program. [Preview Abstract] |
Friday, October 6, 2006 12:06PM - 12:18PM |
B2.00009: Optimized controller design for an ECDL locked to at optical cavity James Archibald, Brian Neyenhuis, Matthew Washburn, W. Sam Weyerman, Sean Warnick, Dallin Durfee We have performed a study of optimized feedback control of an external-cavity diode laser (ECDL) locked to a high-finesse optical cavity. We have measured the response of the laser to current modulation and developed a mathematical model of our laser. Using this model, we have calculated optimized designs for the feedback controller which keeps the laser locked to the optical cavity. [Preview Abstract] |
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