Colloquia are Wednesdays at 4:00 p.m. in DUAN G1B20, unless otherwise noted.

Coffee, tea and cookies will be available before regular colloquia beginning at 3:45 p.m. in DUAN G1B31.

October 25 — "Generation and Application of Attosecond Laser Pulses"

  • Presenter: Andreas Becker, JILA, University of Colorado, Boulder
  • Host: John Price
  • Abstract: High harmonic generation provides a unique technique to generate coherent light up to keV photon energies, which is emitted in pulses a few tens of attoseconds in duration. Such pulses can now be used to probe dynamics in matter on the time scale of electronic motion. I will present our theoretical efforts to perform numerical calculations capturing the highly nonlinear process of attosecond pulse generation on both the microscopic level of a single atom and the macroscopic level of the generating gas medium consisting of billions of atoms. In the second part I will then discuss examples of the application of attosecond pulses to resolve electron dynamics in atoms and molecules.

November 1 — "Transient Crosslinkers Tune the Patterns of Microtubule Filaments"

  • Presenter: Jennifer Ross, University of Massachussetts, Amherst 
  • Host: Meredith Betterton
  • Jennifer Ross Research imageAbstract: The cell is a complex autonomous machine taking in information, performing computations, and responding to the environment. To enable agile read/write capabilities, much of the molecular biochemistry that performs these computations must be transient and weak, allowing signals to be carried as a function of the concentration of numerous and coupled interactions. Traditionally, biochemical experiments can only measure strongly interacting systems that can last for long times in dilute concentrations. We have developed microscopy measurements to enable to visualization of weak, transient interactions and the resulting emergent behaviors of coupled systems. I will present excerpts from stories where many weak, transient interactions can have strong repercussions on the overall activity and can, in fact, overpower strongly interacting systems. These studies involve the microtubule cytoskeleton and the transport motor, kinesin-1.  Our results reveal a fundamentally important aspect of cellular self-organization: weak, transient interacting species can tune their interaction strength directly by tuning the local concentration to act like a rheostat. The tunability of weak, transient interactions is a fundamental activity of biological systems, and our insights will ultimately enable us to learn how to engineer these systems to create biological or biomimetic devices.

    Biography: Ross is the director of the new Massachusetts Center for Autonomous Materials (MassCAM) and an award-winning biophysicist studying the organization of the microtubule cytoskeleton and microtubule-based enzymes using high-resolution single molecule imaging techniques. She has a degree in Physics and has studied the microtubule cytoskeleton for over a decade. As a Cottrell Scholar, Ross has pioneered innovative teaching techniques that are being adopted around the world. Specifically, she has taught at several international short courses on microscopy including Analytical and Quantitative Microscopy (AQLM) at the Marine Biology Laboratory and the Bangalore Microscopy Course at the National Centre for Biological Science in Bangalore, India. She has also served as the President of NESM in the past. She is also an advocate for women and under-represented groups and has a blog to help others make it in academics.

November 8

  • Presenter: Mark Kasevich, Stanford University
  • Host: Scott Diddams
  • Abstract: 

November 15 

  • Presenter: 
  • Host: 
  • Abstract: 

November 22 — Fall Break; No Colloquium

November 29

  • Presenter: Sridhara Dasu, University of Wisconsin 
  • Host: 
  • Abstract:

December 6

  • Presenter: Mark Saffman, University of Wisconsin 
  • Host: 
  • Abstract: 

December 13

  • Presenter: Lindley Winslow, MIT
  • Host: Alysia Marino
  • Abstract: 

Previous Colloquia

August 30 — "What are Saturn’s rings made of?"

  • Presenter: Sascha Kempf, University of Colorado, Boulder
  • Host: 
  • Abstract: When Galileo Galilei discovered Saturn’s rings 450 years ago he didn’t even know that he had observed rings. It was Christiaan Huygens who proposed that Saturn is surrounded by a thin solid ring - made of metal. Earth-based spectroscopic observations in 1970 revealed that the rings in fact consist of 95% clean water ice, but the nature of the other 5% of embedded material, which gives the rings their unique reddish tint, is still unknown. It is, however, this little amount of unknown material that will bring us closer to understanding the rings’ origin and provide valuable information about the formation of the Saturnian system as a whole.

    After almost 20 years in space, NASA's Cassini spacecraft has begun the final chapter of its remarkable story of exploration: its Grand Finale. Before the spacecraft plunges into Saturn’s atmosphere Cassini is undertaking a daring set of orbits that is, in many ways, a whole new mission. Starting in late April this year Cassini is performing weekly dives between the planet and the inner rim of Saturn’s rings. No other mission has ever explored this region that has been considered until a few years ago to be inaccessible for space probes. Those unique orbits allowed the Cosmic Dust Analyzer (CDA) on Cassini for the very first time to collect material originating from the main rings itself and to identify their composition.

    In my talk I will report about the exciting findings by CDA during Cassini’s swan song. 

September 6 — "Generation and detection of tunable orbital angular momentum in polarization-maintaining optical fiber"

  • Presenter: Juliet Gopinath, University of Colorado, Boulder
  • Host: John Price
  • Abstract: In the past few years, twisted light, or light with orbital angular momentum (OAM) has captured interest a diverse array of applications. It can be used to drive micromachines and in biophotonics, OAM is used in microscopy to achieve resolution orders of magnitude better than the diffraction limit. In astronomy, the OAM of light from distant stars carries information about the inhomogeneity of the interstellar medium and the shape of black holes. In quantum information science, OAM states can be entangled, which leads to surprising demonstrations of quantum mechanics and potentially new computational possibilities. OAM-enabled communications, of all the applications, has received the majority of the attention due to the potential increase in fiber optic bandwidth that would be realized in a move from binary to a classical or quantum mechanical-vast parameter space per photon provided by the integer OAM states.

    To date, specialty fiber has been used to carry OAM. In this talk, I will describe new methods for generating OAM light in commercially available polarization maintaining optical fiber. By adding up two higher order modes, generation of tunable OAM can be demonstrated. In addition, I will discuss a new quantitative detection method for light with OAM and extensions of the technique. Finally, I will present a method to control independently, both the OAM and the spatial beam profile.

    Biography: Juliet Gopinath is an Associate Professor of Electrical, Computer and Energy Engineering at the University of Colorado Boulder. She received her B.S. degree in Electrical Engineering from the University of Minnesota and her M.S. and Ph.D. degrees at MIT. She worked at MIT Lincoln Laboratory from 2005 to 2009 on topics including cryogenic Yb:YAG lasers, beam combining, and mode-locked diode lasers. Since 2009, she has run a group focused on optical devices and lasers at CU Boulder. Her current research interests include ultrafast lasers, nonlinear optics, mid-infrared materials, spectroscopy, orbital angular momentum and adaptive optical devices. She is the recipient of an Air Force Young Investigator Award (2010), R & D 100 Award (2012), an NSF CAREER award (2016), the CU Provost Achievement Award (2016) and is an Associate Editor for IEEE Photonics Journal.

September 13 — "Enabling Technology Innovation through Plasma Modeling: Sustainability and Biotechnology as the Next Frontiers"

  • Presenter: Mark Kushner, University of Michigan
  • Host: John Cary
  • Abstract: The field of low temperature plasmas (LTPs) has provided enabling sciences and technologies that are arguably responsible for huge swaths of our industrial and high technology infrastructure.  The information technology revolution has been singularly enabled by the ability to fabricate microchips using LTPs.  Virtually every human implant is fabricated or made biocompatible using LTPs.  All non-incandescent lighting sources rely on LTPs, either directly as the source of photons or indirectly through materials fabrication.  The current generation of jet engines are enabled by LTP processing, and interplanetary missions are made possible by LTP propulsion.  Now, LTPs have the potential to treat wounds and disease, and to convert green-house gases to high value chemicals.  Many of these advances are the end result of scientifically and experimentally inspired technology development, and in some cases incremental advances over many years, with little input from modeling.  The plasma chemistry and plasma surface interactions that are responsible for these successes have untold complexity that acutely challenge diagnostics and modeling, as well as the underlying AMO (atomic, molecular, optical) physics knowledge base.  A legitimate question is – has modeling and simulation been significantly influential in the development of LTP enabled technologies?  Are modeling and simulation LTPs capable of leading innovation?  In this talk, the role and potential of modeling and simulation in the LTP innovation chain will be reviewed with examples from materials processing and the next frontiers of biotechnology and sustainability.  Examples of where modeling has provided insights that stimulated, if not enabled, technology development will be discussed.

September 20 — "ColdQuanta Incorporated: The History and Future of a University Spinoff Company*"

  • Presenter: Dana Anderson, JILA, University of Colorado, Boulder
  • Host: John Price
  • Abstract: ColdQuanta Inc. was founded in 2007 by three physicists and a businessman, myself, Theodor Hänsch, Jakob Reichel and Rainer Kunz.  Its mission is to develop and commercialize cold and ultracold matter technology that can enable the scientific and applications communities.  Much of ColdQuanta’s early technology emerged from a MURI grant from the Army Research Office and more so, a large DARPA grant to develop technology for guided Bose-Einstein Condensate (BEC) applications. Out of that effort came compact components for producing ultracold matter and in particular a sophisticated “atom chip” technology that made it possible to considerably reduce the size of BEC machines and similar systems.  A BEC machine that in the past took many months to build, occupied a large optical table and needed racks of electronic instrumentation can now be purchased from ColdQuanta, occupies a single rack, and can be up and running in six hours.  Since 2007 ColdQuanta has produced instruments for making cold atoms in undergraduate labs, and has enabled numerous applications and scientific experiments from optical lattices to quantum computing to the JPL/NASA mission to put cold atoms on the International Space Station.  This talk tells the story of how ColdQuanta was formed and highlights the role of students and spin-off companies in the University’s mission to provide an educated workforce, to promote scientific advancement, and to maintain this nation’s technological leadership.  It also covers some relevant “this is reality” topics such as starting a tech business, money, and conflicts of interest.  Regarding the latter: 

    *I hereby disclose that I have a financial interest in ColdQuanta, Inc. (!)

September 27 — "The Quest for the New Standard Model: Searching for BSM Physics with Rare-Isotope Beams"

  • Presenter: Kyle Leach, Colorado School of Mines
  • Host: Eric Zimmerman
  • Abstract: The development of the Standard Model (SM) has been one of the crowning achievements in modern physics, and is the cornerstone of current subatomic studies. Despite its success, the SM is known to be incomplete, and providing limits on possible physics beyond the Standard Model (BSM) is crucial to our understanding of the natural universe.  Although they are generally complex, atomic nuclei can be exploited as a laboratory for these studies through the use of rare-isotope beams (RIBs).  The production of these short-lived, very exotic isotopes has opened new avenues of research in our search for BSM physics in the era of the LHC.  This work is at the precision and sensitivity frontiers, and helps to bridge the gap between atomic, nuclear, and particle physics using novel, state-of-the-art detection techniques. In this talk, I will use these topics to highlight the significant role of the atomic nucleus in our ongoing search for additional generations of quarks, new descriptions of the weak interaction, and light dark matter. These studies play a critical role in providing the groundwork for our quest to develop the "New Standard Model".

October 4 — "Broadening the Searchlight: New Ideas in Dark Matter Detection"

  • Presenter: Kathryn Zurek, LBNL
  • Host: Ethan Neil
  • Abstract: Searches for massive dark matter have largely focused on a mass window near the weak scale, the so-called "WIMP window". This window is, however, becoming increasingly closed by both the LHC and the unprecedented sensitivity of direct detection experiments. At the same time, theoretical work in recent years has shown lighter dark matter candidates in a hidden sector are theoretically well-motivated, natural and arise generically in many theories beyond the standard model. New ideas are needed to search for dark matter with mass below a GeV and as light as the warm dark matter limit of a keV. We propose new ideas to search for such light dark matter with superconductors, semi-conductors, graphene, Dirac materials, and superfluid helium. We show that these same experiments, through inelastic processes, may also be sensitive to dark matter with masses in the meV to keV mass window, broadening the mass reach to light dark matter by many orders of magnitude.

October 11 — "Spin Orbit Coupled Quantum Magnetism"

  • Presenter: Kate Ross, Colorado State University
  • Host: Chuck Rogers
  • Abstract: Strong quantum fluctuations and spin entanglement can lead to exotic emergent many body properties of materials, such as fractionalized excitations predicted for quantum spin liquids, or the field-tuned Bose Einstein Condensation observed in quantum dimer crystals.  Traditionally, the materials space in which these types of phases are sought has been limited to materials with “pure" spin 1/2, as obtainable from Cu2+ for instance, and most theories have therefore focused on the isotropic exchange limit.  However, attention has recently shifted towards quantum materials in which an interplay of strong spin orbit coupling and crystal electric field effects lead to a "pseudo-spin" 1/2.  The magnetic interactions in these materials can be described by anisotropic effective exchange models, which can lead to new predicted quantum many body phenomena such as the Majorana fermion excitations of Kitaev quantum spin liquid, or emergent electrodynamics in quantum spin ice.  I will discuss some recent material examples that exemplify this new paradigm.

October 18 — "The Remarkable Ways in Which Gases Dissolve and React in Water"

  • Presenter: Gilbert Nathanson, Department of Chemistry, University of Wisconsin, Madison
  • Host: David Nesbitt
  • Abstract: Interfacial reactions between atmospheric gases and sea spray play a vital role in our air quality and climate.  These reactions also display fascinating dynamics at the atomic scale.  From this microscopic perspective, the interfacial encounter begins when gas molecules strike the surface of an aqueous solution that might contain ions and biological molecules.  We rely on understanding the physics of these gas-liquid collisions to construct a “blow-by-blow” picture of the solvation and reaction of acids, bases, and oxidizers in such complex solutions.  I will describe experiments using microjets and coated wheels that enable us to explore sea-spray mimics inside a vacuum chamber and help reveal how aerosol-mediated reactions takes place.

For more information about colloquia this semester, contact: John Price.