UNB Physics Department Visiting Speaker Dr. Anantharaman Kumarakrishnan-FR

Event Details:

Dr. Anantharaman Kumarakrishnan will be visiting UNB to give a talk on his research titled, Precise Time Domain Measurements of Diffusion of Microparticles and Atoms. Dr. Kumarakrishnan is an experimentalist working in atom interferometry at York University in Toronto since 2000. His research group has developed auto-locking lasers for applications in precision metrology that include studies of ultracold atoms, precision measurements of diffusion for the development of atomic vapour magnetometers, rapid characterization of particles confined by optical tweezers and accurate determination of atomic lifetimes. His doctoral research at the University of Idaho investigated the properties of superfluorescent amplifiers with lidar applications in the mid-infrared wavelengths. During postdoctoral appointments at U. Connecticut, NYU and MIT, he was involved with some of the first studies of the properties of magneto-optical traps, and the development of the first single-state atom interferometer using cold atoms. His group has also developed two high-profile upper-level laboratory courses on laser spectroscopy and atom trapping with industrial support.

Abstract: We describe a simple technique for the rapid determination of the mass of microparticles confined in a free-space optical dipole force trap. The technique relies on direct imaging of drop-and-restore experiments without the need for a vacuum environment. In these experiments, the trapping light is rapidly shuttered with an acousto-optic modulator, causing the particle to be released from and subsequently recaptured by the trapping force while undergoing diffusive motion. The trajectories of both the falls and restorations, imaged using a high-speed CMOS sensor, are combined to determine the particle mass. We corroborate these measurements using an analysis of position autocorrelation functions and the mean-square displacement of the trapped particles. We report a statistical uncertainty of less than 2% for masses on the order of 10^-14 kg using a data acquisition time of approximately 90 s. We then extend our studies of diffusion to atoms moving on similar length scales by demonstrating a technique for the most accurate measurement of diffusion coefficients for rubidium atoms in a buffer gas environment. Here, we rely on establishing and detecting an optical lattice of Rb atoms using a coherent transient technique. Our measurements can be used to model the performance of atomic vapour cell magnetometers and develop a pressure sensor that depends on the intrinsic properties of atoms.

Building: Toole Hall

Room Number: 3