Research

My research is focused on the interactions between matter and electromagnetic fields. These interactions are fundamental to a vast number of impactful technologies. As just a few examples, consider the lasers, cameras, particle detectors which have had transformative impact in communication, medicine, defense, and basic research. All of these devices, while seemingly very different, exploit the interaction of light and matter (in many different guises!).

Recent discoveries – in condensed matter physics, in nanophotonics, and in quantum optics – enable the interactions between light and matter to be tailored almost at will; to the point where the interactions can enter regimes that do not occur in natural materials. Such new regimes promise a range of disruptive technologies with applications in quantum sensing and metrology, quantum information processing, spectroscopy, and beyond. Such applications promise to be the same caliber of widespread impact as established technologies resulting from the interactions of light and matter. Some topics we study in service of this goal include collective excitations in solids, 2D materials, strong coupling of light and matter, nanophotonics, lasers, and quantum nonlinear optics.

Below you’ll see an overview of some of the fields I have worked on, and some representative publications.

Light-matter interactions with photonic quasiparticles

When electrons in quantum emitters interact with tightly confined photonic quasiparticles associated with collective excitations in materials, many new decay channels open up for that emitter. This can make the observed emission spectrum of an emitter appear fundamentally differently (bottom) from the conventional case, where only a small set of optical transitions are efficient enough to be observed [Image taken from Science 353.6296 (2016): 263-269.].

Recent work in controlling collective electromagnetic excitations in solids (e.g., plasmons, optical phonons, excitons) enable confinement of electromagnetic energy down to very small volumes. These “shrunken photons” or “photonic quasiparticles”, interact with electrons very differently from photons in vacuum, enabling many new effects, as well as technologies. For some of our work on formulating the laws of light-matter interactions with photonic quasiparticles (in perturbative and non-perturbative regimes), see:

Lasers and masers that replace the photon with photonic quasiparticles produced by non-perturbative light-matter coupling can behave fundamentally differently from lasers and masers that exist. Rather than producing Glauber coherent states, as lasers and masers do, these “exotic” lasers can deterministically produce large non-classical states, such as Fock states. [Image taken from arXiv:2111.07010 (2021).]

Such strong interactions, when taken to non-perturbative regimes, can also lead to fundamentally new nonlinearities that are not found in ordinary materials. These nonlinearities can be of much higher “order” than say third-order Kerr nonlinearities in conventional materials, and can form the basis for new types of optoelectronic devices. For example, such nonlinearities can lead to the development of lasers that produce macroscopic non-classical light, such as Fock states. For our recent theoretical predictions on this work, see:

  • Nicholas Rivera, Jamison Sloan, Yannick Salamin, and Marin Soljačić. “Macroscopic condensation of photon noise in sharply nonlinear dissipative systems.” arXiv:2111.03099.
  • Nicholas Rivera, Jamison Sloan, Ido Kaminer, and Marin Soljačić. “Fock lasers based on deep-strong coupling of light and matter.” arXiv:2111.07010.

Beyond these areas, I also have worked on a number of other topics, with relevant publications below.

Quantum optical effects with free electrons

An energetic electron flying by an electromagnetic medium can scatter off of vacuum fluctuating near-fields. In doing so, it can Doppler shift those fluctuations, leading to the emission of high-energy photons, such as X-rays. This new type of vacuum force acting on charged particles is equivalently understood as a quantum-optical two-photon process in which the electron simultaneously emits one excitation of the medium (a photonic quasiparticle) and a high-energy photon. The two-photons can be entangled together. [Image taken from Nature Physics 15.12 (2019): 1284-1289.]

Phononics in 2D materials

Optical phonons in 2D materials (like monolayer boron nitride) support tight evanescently-confined electromagnetic fields down to very tight dimensions, approaching the atomic scale. Such tight-confinement can facilitate extremely strong interactions with emitters in the mid-infrared, potentially enabling the development of quantum sources such as atoms which preferentially emit entangled pairs of phonon polaritons [Image related to Nano Letters 19.4 (2019):2653-2660. Image credit: Thomas Christensen.]