Alexander Papageorge

Supermode-density-wave-polariton condensation with a Bose–Einstein condensate in a multimode cavity

Phase transitions, where observable properties of a many-body system change discontinuously, can occur in both open and closed systems. By placing cold atoms in optical cavities and inducing strong coupling between light and excitations of the atoms, one can experimentally study phase transitions of open quantum systems. Here we observe and study a non-equilibrium phase transition, the condensation of supermode-density-wave polaritons. These polaritons are formed from a superposition of cavity photon eigenmodes (a supermode), coupled to atomic density waves of a quantum gas. As the cavity supports multiple photon spatial modes and because the light–matter coupling can be comparable to the energy splitting of these modes, the composition of the supermode polariton is changed by the light–matter coupling on condensation. By demonstrating the ability to observe and understand density-wave-polariton condensation in the few-mode-degenerate cavity regime, our results show the potential to study similar questions in fully multimode cavities.

An adjustable-length cavity and Bose–Einstein condensate apparatus for multimode cavity QED

We present a novel cavity QED system in which a Bose-Einstein condensate (BEC) is trapped within a high-finesse optical cavity whose length may be adjusted to access both single-mode and multimode configurations. We demonstrate the coupling of an atomic ensemble to the cavity in both configurations. The atoms are confined either within an intracavity far-off-resonance optical dipole trap (FORT) or a crossed optical dipole trap via transversely oriented lasers. Multimode cavity QED provides fully emergent and dynamical optical lattices for intracavity BECs. Such systems will enable explorations of quantum soft matter, including superfluid smectics, superfluid glasses, and spin glasses as well as neuromorphic associative memory.

Probing of single quantum dot dressed states via an off-resonant cavity

Coherent interaction between a quantum dot and a resonant laser is observed through an incoherent read-out channel created by coupling to an off-resonant cavity. Under bichromatic driving of the quantum dot optical output collected from the off-resonant cavity exhibits two peaks, a signature of Rabi-side bands that matches closely with our theoretical model. The off-resonant cavity provides a convenient method for resonant quantum dot spectroscopy and quantum dot state readout.

Coupling to modes of a near-confocal optical resonator using a digital light modulator

Digital micromirror devices (DMD) provide a robust platform with which to implement digital holography, in principle providing the means to rapidly generate propagating transverse electromagnetic fields with arbitrary mode profiles at visible and IR wavelengths. We use a DMD to probe a Fabry-Pérot cavity in single-mode and near-degenerate confocal configurations. Pumping arbitrary modes of the cavity is possible with excellent specificity by virtue of the spatial overlap between the incident light field and the cavity mode.

Bichromatic driving of a solid-state cavity quantum electrodynamics system

We theoretically study the bichromatic driving of a solid-state cavity quantum electrodynamics (QED) system as a means of probing cavity dressed state transitions and observing the coherent interaction between the system and the light field. We show that this method can enable the observation of the higher order cavity dressed states, supersplitting and ac-Stark shift in a solid-state system comprised of a quantum dot (QD) strongly coupled to a photonic crystal cavity for the on- and far off-resonant cases. For the off-resonant case, phonons mediate off-resonant coupling between the QD and the photonic resonator, a phenomenon unique to solid-state cavity QED.

Coherent optical spectroscopy of a single quantum dot via an off-resonant cavity

Coherent interaction between a quantum dot and a resonant laser is observed through an incoherent read-out channel created by coupling to an off-resonant cavity. Under bichromatic driving of the quantum dot optical output collected from the off-resonant cavity exhibits two peaks, a signature of Rabi-side bands that matches closely with our theoretical model. The off-resonant cavity provides a convenient method for resonant quantum dot spectroscopy and quantum dot state readout.

Erratum: An adjustable-length cavity and Bose?Einstein condensate apparatus for multimode cavity QED (2015 New J. Phys. 17 043012)

Wepresent a novel cavityQED system inwhich a Bose–Einstein condensate (BEC) is trappedwithin a high-finesse optical cavity whose lengthmay be adjusted to access both single-mode andmultimode configurations.We demonstrate the coupling of an atomic ensemble to the cavity in both configurations andmeasure that the single-atom, TEM0,0-mode cooperativity exceeds unity. The atoms are confined either within an intracavity far-off-resonance optical dipole trap or a crossed optical dipole trap via transversely oriented lasers.Multimode cavityQEDprovides fully emergent and dynamical optical lattices for intracavity BECs, in that the process of atomic self-organizationmay be described as a continuous symmetry breaking phase transition resulting in the emergence of a compliant lattice with phonon-like excitations. Such systemswill enable explorations of quantum soft matter, including superfluid smectics, superfluid glasses, and spin glasses as well as neuromorphic associativememory.

Photonic crystal cavities: From nonlinear optics at a few photons level, to fast, energy efficient information processing

A combination of a single quantum emitter (a semiconductor quantum dot) with a semiconductor optical nanocavity has been employed to demonstrate devices ranging from optical switches and modulators controlled with sub-fJ energies, to quantum sources.

Quantum Dot Dressing Observed via Off-resonant Cavity

Signatures of dressing of a single quantum dot by a strong resonant laser are observed by monitoring the off-resonant cavity emission.

Opto-mechanics and quantum dot-nanocavity QED

Phonon assisted interaction between a quantum dot and an off-resonant nanocavity has been studied and employed for coherent quantum dot spectroscopy.