Optical Physics

Optical physics studies the interactions of light with atoms, molecules and semiconductor systems in different contexts. At the College of Optical Sciences, nine different research groups pursue projects in quantum gases, quantum information, theoretical and computational optical physics, experimental and theoretical semiconductor quantum optics, and ultrafast lasers, with impacts to the theory and applications of high-harmonic generation, laser cooling and trapping, quantum control, and much more.

What's New in Optical Physics at The College of Optical Sciences

Quantum Gases Group

quantum turbulence in a BEC

Vortices showing quantum turbulence in a BEC.

Brian P. Anderson's Quantum Gases Group uses laser light to cool gases of rubidium atoms to a few billionths of a degree above absolute zero. These atomic fluid droplets, called Bose-Einstein condensates, follow the laws of quantum physics and serve as valuable tools for exploring fundamental physics topics such as quantum turbulence, the primary concern of the Anderson group. BEC turbulence is indicated by the motion of vortices, microscopic holes that identify fluid circulation like the eyes of tiny hurricanes. New regimes of quantum fluid dynamics and quantum turbulence can be discovered by watching how these vortices move and interact.

Theoretical Solid-State Optics Group

optically pumped semiconductor microcavities

Optically pumped semiconductor microcavities exhibiting near-field and far-field patterns in the polariton quantum fluid.

The Theoretical Solid-State Optics Group led by Rolf Binder focuses on the optical properties of semiconductor structures. Using microscopic quantum-mechanical many-body theories, including nonequilibrium Green's functions, the group pursues projects ranging from basic physical studies to application-oriented simulations. Recent and ongoing examples include slow- and fast-light effects in bulk semiconductors and semiconductor heterostructures, optical refrigeration of semiconductors, optical and elastic properties of semiconductor nanomembranes, optical properties of graphene, and pattern formation and control in quantum fluids realized by exciton polaritons in semiconductor microcavities.

Quantum Information and Control Group

Ultracold atoms

Experiment for production and quantum control of ultracold atoms.

Poul Jessen's Quantum Information and Control Group investigates fundamental problems in quantum information science using ultracold atoms. One project uses Zeeman sublevels in the electronic ground state of atomic cesium to explore computer-optimized quantum control, quantum tomography and quantum chaos. A second project creates many-atom spin-squeezed states through quantum measurement back-action, with the long-term goal of improving quantum-limited atomic clocks and sensors. A third project traps atoms in the evanescent field around an optical nanofiber, with the aim of developing an atom-light quantum interface.

Ultrafast Lasers Group

Ionization of Xenon

Ionization of xenon during intracavity high-harmonic generation.

The Ultrafast Lasers Group headed by R. Jason Jones employs novel light sources, such as the femtosecond frequency comb generated by a phase-stabilized train of ultrashort pulses, for experimental ultrafast optical science and precision laser spectroscopy. Such sources have enabled studies of temporal dynamics in light-matter interactions ranging from attosecond to several-second time scales, leading to the development of new atomic clocks and subfemtosecond timing.

Current activities include precision spectroscopy of laser-cooled mercury and the development of frequency comb sources in the extreme-ultraviolet based on intracavity high-harmonic generation.

Quantum Nano-Optics Group

model of silver dipole antenna

Model of silver dipole antenna coupled to near-surface indium-gallium-arsenide quantum well.

Galina Khitrova's Quantum Nano-Optics of Semiconductors Group conducts experimental studies of the light-matter interaction of semiconductor heterostructures (quantum wells and dots) coupled to nanoscale optical cavities. Recently, this has led to the investigation of metallic cavities that allow light to be confined to regions one thousand times smaller than typical dielectric cavities, which creates a large vacuum electromagnetic field that greatly alters the dynamics of the c oupled quantum emitter. Among the group's goals is to use these nanocavities to demonstrate Purcell enhancement of spontaneous emission and cooperative emission from semiconductor quantum dots.

Theoretical and Computational Optical Physics Group

The Theoretical and Computational Optical Physics Group led by Miroslav Kolesik explores the intersection of modern nonlinear optics, atomic and molecular physics, and strong-field phenomena. Research interests span statistical mechanics, Monte Carlo simulation, critical phenomena, nonequilibrium and driven systems, semiconductor laser simulation and optics; current activity concentrates on computational optics, particularly ultrashort optical pulse interactions.

Recent work includes first-principle methods to describe light-matter interactions in regimes that defy the tools and notions of traditional nonlinear optics and that scale from the quantum through the optical to the macroscopic. The challenge is in the integration of the microscopic medium description into space- and time-resolved, realistic simulations of experiments. Substantial research is being done in close collaboration with teams in the U.S. and Europe.

Optical Physics Group

reflecting light

Light reflected from a hollow cone undergoing changes in spin and orbital angular momentum, as shown by the variation of the Poynting vector and phase in transverse plane.

Masud Mansuripur's Optical Physics Group researches optical-magnetic-macromolecular data storage, light-matter interaction, magneto-optical effects and the mechanical effects of light involving the exchange of linear and angular momenta between electromagnetic fields and material media.

As an example of the latter effects, the figure above shows a hollow metallic cone with an apex angle of 90 degrees, illuminated by a circularly polarized light beam. Upon reflection from the cone, the spin angular momentum of the beam is reversed. However, no angular momentum is transferred to the cone, because the reflected beam picks up an orbital angular momentum twice as large but opposite in direction to that of its spin. The figure also shows profiles of the phase and the Poynting vector in the cross-sectional plane of the reflected beam.

Theoretical-Computational Optical Physics and Applied Mathematics Group

The Theoretical-Computational Optical Physics and Applied Mathematics Group led by Jerome V. Moloney studies ultrashort laser pulse interaction with gases and condensed media under extreme conditions. Extreme intensities acting over tens to hundreds of femtoseconds strip and accelerate electrons from an atom, creating anisotropic distributions of electrons and ions that eventually equilibrate to form a plasma channel. This channel acts like an extended conducting wire and can direct high-voltage charges and, potentially, lightning strikes. Accompanying this explosive event is the creation of a white light super-continuum source that can be used to perform remote spectroscopy and detect atmospheric molecules and pollutants at multikilometer ranges.

In another activity, Moloney's team is designing new classes of high-power ultrashort-pulsed semiconductor disk lasers using first principles quantum many-body theory, processing these into laser devices and demonstrating them in the laboratory.

Theoretical Optical Physics Group

The Theoretical Optical Physics Group headed by Ewan M. Wright conducts research across a broad area including nonlinear optics, the physics of ultracold gases and the exploration of novel laser beams. Key theoretical contributions include the elucidation of the physics underlying light string propagation in media such as air, the early treatment of the field of nonlinear atom optics and the optical binding of nanoparticles.

Optical Physics Faculty

Anderson's research involves the study of quantum fluid dynamics and quantum turbulence in dilute-gas Bose-Einstein condensates, or BECs. These tiny droplets of superfluid are the coldest known objects in the universe and are created using laser cooling and atom trapping techniques. They also provide a unique and versatile medium for the experiments of quantum fluid dynamics in Anderson’s lab at the College of Optical Sciences. In a superfluid such as a BEC, microscopic centers of fluid circulation called quantized vortices may be observed using optical techniques and are conspicuous indicators of the system’s superfluid dynamics. By studying the way vortices are generated and how they move and interact, a wide range of general physical phenomena well beyond Bose-Einstein condensation may be better understood. Examples include phase transition dynamics, turbulence, reduced-dimensional quantum physics and the dynamics of quantum systems far from equilibrium.

Anderson was a member of the research team that first created and observed quantized vortices in BECs in 1999, and since then has been primarily involved in experimental, numerical and theoretical studies of vortex creation, manipulation and dynamics in BECs. Current efforts in his laboratory focus on:

  1. developing new methods for vortex generation and manipulation with laser beams for controlled studies of vortex dynamics,
  2. studying the dynamics and statistics of vortices of two-dimensional quantum turbulence and
  3. development of new methods for studying and observing vortices in BECs.

The main research focus in our group is on theoretical investigations of the optical properties of semiconductor structures. Our fundamental theoretical investigations of semiconductors are based on microscopic quantum-mechanical many-body theories and include ultrafast nonlinear optical processes in bulk semiconductors and quantum-well structures. Recent examples of research projects include electromagnetically-induced transparency, slow light effects in semiconductor heterostructures, nonlinear spectroscopy and applications of Bragg-spaced multiple quantum wells, optical refrigeration of semiconductors, optical four-wave mixing instabilities in semiconductor quantum wells systems, including microcavities, and excitonic response of semiconductor nanomembranes. In addition to the semiconductor research, we are investigating optical refrigeration in optical fibers.

Semiconductor cavity QED is the main research theme of our group. We are using single quantum dots instead of atoms as in atomic QED and nanocavities. Our group was the first to observe vacuum Rabi splitting between a single InAs quantum dot and a GaAs photonic crystal slab nanocavity; Nature 432, 200 (2004) had 851 citations as of July 14, 2012. At present we are focused on coupling between a quantum dot or quantum well with metallic nanocavities having much smaller volumes than the dielectric 2-D photonic crystal slab nanocavity. We are also investigating atomic layer deposition of Er onto 1-D photonic crystal silicon nanobeams to bring light sources into silicon for our NSF ERC Center for Integrated Access Networks.

  • Meinel 664: Low-temperature high-spatial-resolution cw spectroscopy laboratory. Includes cw Ti:Sa laser, low-temperature Cryovac cryostat with internal nano-positioners, 1.26 m Spex spectrometer and 512 linear InGaAs detector array. Used to study light-semiconductor coupling, both photonic crystal nanocavity with single quantum dot and metallic nanoantennae with single quantum wire or dot.
  • Meinel 670: MBE growth characterization laboratory. Includes atomic force microscope, broadband linear transmission and reflection setup, and fiber loop for measuring the quality factor of nanobeam cavities.
  • Meinel 676: Femtosecond pump-probe spectroscopy laboratory. Includes our fs Ti:Sa laser, an Oxford low-temperature cryostat, various spectrometers and detectors, and a streak camera. Photoluminescence and nonlinear pump-probe measurements on a wide variety of MBE grown heterostructures are studied.
  • Meinel 678: MBE machine for growing microcavities, quantum wells, wires, dots on GaAs or InP substrates.

My research is theoretical and computational in nature and is in the general area of optical physics. Recent research highlights include propagation of light strings in gases, theory and simulation of high-harmonic generation in optical cavities, and proposal of an optical spring mirror for quantum optomechanics.