Bulletin of the American Physical Society
Fall 2009 Meeting of the Four Corners Section of the APS
Volume 54, Number 14
Friday–Saturday, October 23–24, 2009; Golden, Colorado
Session F3: Symposium on Advanced Optical Measurements III: Microscopy |
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Chair: Jeff Squier, Colorado School of Mines Room: Green Center 249 |
Saturday, October 24, 2009 8:00AM - 8:12AM |
F3.00001: Axial-scanning techniques for multiphoton imaging Michael Young, Erich Hoover, Eric Chandler, Jeffrey Field, Jeff Squier \hyphenpenalty=5000 We have developed a novel multiphoton imaging system that is capable of imaging multiple focal planes simultaneously. In this talk, we describe a new method that enables us to electronically control the offset of the focal planes by up to 80 micrometers with little or no degradation in focus (diffraction-limited sectioning is maintained as the focal planes are shifted). This method of shifting the focus will enable access to arbitrary focal planes, e.g., focal planes that are rotated with respect to one another. By exploiting this new capability, this microscope will greatly facilitate the study of biological systems. [Preview Abstract] |
Saturday, October 24, 2009 8:12AM - 8:24AM |
F3.00002: Using FPGAs for Simultaneous Photon Counting Imaging of Multiple Focal Planes Erich Hoover, Eric Chandler, Jeff Field, Kraig Sheetz, Ram\'{o}n Carriles, Jeff Squier \hyphenation{electronics instead repetition without attention} Photon counting detection has been shown to provide significant signal-to-noise improvements in multi-photon microscopy. However, due to the time scales involved, it is non-trivial to assemble the necessary electronics to process PMT analog voltage signals into an image. By instead building the necessary logic inside of a Field Programmable Gate Array, photon counting imaging becomes tractable. This method also easily permits extending beyond simple 2D imaging into de-multiplexing data obtained from multiple focal planes nearly simultaneously. Given sufficient hardware, such a system can also be used to stream image data back to a PC and record video from each focal plane. Since imaging with a multi-photon microscope typically involves signals with repetition rates in the hundreds of megahertz, such imaging will not succeed without attention to seemingly minor details in the circuit design. This talk will present our photon-counting circuit design within the context of our imaging system. [Preview Abstract] |
Saturday, October 24, 2009 8:24AM - 8:36AM |
F3.00003: Coherence modulated third harmonic generation for interface vibrational spectroscopy Jesse Wilson, David Kupka, Omid Masihzadeh, Randy Bartels Though third harmonic generation (THG) by tightly focused beams at an interface is generated in bulk regions of the two surrounding materials, we demonstrate measurement of surface-specific vibrational information by coherence-modulated THG (CM-THG). In CM-THG, a tightly focused ultrafast pulse in the presence of an impulsively-prepared vibrational coherence will undergo modulation by the coherence during the THG process. Measuring the CM-THG signal as a function of scanning the interface allows separation of bulk and interface phonon oscillation contributions to the CM-THG signal. Three distinct processes occur leading to modulation of the detected third harmonic signal by the coherence: 1) The third harmonic generation itself is modulated by the coherence through a transient nonlinear susceptibility, i.e. coherent second hyper-Raman scattering (CSHRS); 2) the fundamental is modulated by transient linear susceptibility cascading to the third harmonic; and 3) the index of refraction at the boundary modulates the fundamental prior to third harmonic generation in air after the sample interface. To our knowledge, this is the first measurement of CSHRS. Though hyper-Raman selection rules have been proposed, no experimental verification has yet been performed. [Preview Abstract] |
Saturday, October 24, 2009 8:36AM - 8:48AM |
F3.00004: Detection at the single molecule level using an optical fiber Thomas Topel, Brian Mong, Wei-Ting Chen, William Fairbank We are developing a method for detecting single Ba+ ions in solid xenon on a fiber probe for the EXO double beta decay experiment. As a demonstration of potential capability, we have explored detection of Rhodamine 6G molecules and quantum dots in solution using the same optical setup. We report results on detection of $\sim $1 dye molecule on the average in the probe volume and attempts to do the same with quantum dots. Steps to fix single dye molecules or quantum dots in position and observe blinking from single molecules or dots will follow. [Preview Abstract] |
Saturday, October 24, 2009 8:48AM - 9:00AM |
F3.00005: State of the art in Van der Waals atom-surface potential measurements Vincent Lonij, Cathy Klauss, Will Holmgren, Alex Cronin Van der Waals and Casimir-Polder potentials are the dominant interactions between charge-neutral objects at nano- to micrometer length scales. As such they have attracted considerable interest in the field of nanotechnology. Understanding of these potentials is important in searches for new forces such as deviations from Newtonian potentials at very short length scales and vacuum friction. We have recently made significant advances in precision measurements of the Van der Waals atom-surface potential strength (C3). Using either interferometer or diffraction experiments we are able to determine the interaction strength (C3) between an atom and a nano-grating with a precision of 6\%. This is a factor of 5 improvement over previous diffraction experiments. We also report ratios of C3 for different atoms with a precision of better than 3\%. At this level of precision we are sensitive to the contribution of core electrons in the atom as well as the geometry of the surface. We have already been able to set an upper limit on the magnitude of non-newtonian potentials for lithium that is competitive with previous limits. [Preview Abstract] |
Saturday, October 24, 2009 9:00AM - 9:12AM |
F3.00006: An all electrical method for measuring ultra-small forces acting on nanowire oscillators Scott Hoch, John Teufel, Joshua Montague, Charles Rogers, Kris Bertness, Konrad Lehnert As nano technology becomes more prevalent in today's world, it is increasingly more important to understand how nanodevices, including mechanical resonators, behave in a range of environments. The purpose of this experiment is to measure small forces exerted on nanowires. The measurement is made using capacitive coupling between a high-Q microwave resonator and the aforementioned nanowire. This technique was used to successfully measure forces smaller than 0.1mirco-Newton on aluminum cantilevers. The experiment is currently being performed to measure forces on the order of 1pico-Newton exerted on Gallium-Nitride nanowires. The apparatus should provide a general, all-electrical method of measuring the motion of nanowire oscillators. [Preview Abstract] |
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