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

Quantum Gases Group

Quantum Turbulence

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

Quantum control of 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

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

Resonant-state landscape of a quantum system

Resonant-state landscape of a quantum system: It allows economic, yet accurate calculation of nonlinear optical properties.

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

Light reflected from a hollow cone undergoing changes

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

Electromagnetic light bullet

Electromagnetic light bullet transports multiple Terawatts of power over hundreds of meters in the atmosphere. Bottom: Snapshots of the bullet at fixed locations along its path. The bullet itself has intensity spikes (in red) and sheds higher harmonic radiation packets in its wake (to its left).

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

optical binding of two, three and four dielectric particles in a host liquid

Simulation and experimental results for the optical binding of two, three and four dielectric particles immersed in a host liquid and illuminated by counter-propagating laser fields. The figures illustrate the field intensity that is detected via fluorescence from an additive to the liquid, and the dark spots reveal the particle positions. Optical binding relies on the fact that the spatial distribution of the particles modifies the light propagation, and the light in turn dictates the optical forces on the particles.

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.