Photonic quasiparticle quantum electrodynamics: each possible photonic quasiparticle can interact with electrons (e.g., free electrons or bound electrons in atoms or molecules) through electromagnetic forces, just like photons in free space interact with electrons. Due to the differences in dispersion and polarization of photonic quasiparticles, a host of light-matter interaction phenomena occur that have no free space analog. Above, a few such examples are diagramatically represented. Subscripts refer to references in [1]; a more expansive set of phenomena is also presented there.

Advances in nanoscience have allowed us as a community to control the propagation and generation of light. One of the most powerful and versatile modern techniques for controlling light is creating “photonic quasiparticles”. When light propagates through a material, it strongly interacts with the underlying material polarization, forming a new effective particle. This “photonic quasiparticle” carries a moving electromagnetic field, just like photons in vacuum, but the underlying properties, such as the energy-momentum dispersion and polarization properties can be very different. When interfacing these photonic quasiparticles with various quantum emitters – such as atomic defects, quantum dots, or free electrons – light emission can be strongly enhanced and controlled. Moreover, a variety of exotic phenomena can be realized that have no analogs with photons in vacuum. Above, we show examples of the many new light-matter interaction phenomena that occur in materials. See e.g., Refs. [2,3] below to see some of those examples (for example in [2], we showed how polariton excitations in 2D materials could enable “forbidden transitions”, while in [3] we showed a new type of vacuum force that acts on charged particles, enabling strong X-ray emission without strong applied magnetic fields).

Importantly, these photonic quasiparticles can also be strongly shaped by the underlying material geometry. For example, by spatially modulating the refractive index of a material on the scale of the photon wavelength, the density of photonic states can be strongly controlled, and the absorption and emission of light can be strongly enhanced. Controlling light in this way is the foundation of the field called “nanophotonics” which has already enabled transformative applications in light generation, communications, and laser technology. Broadly, many new applications of nanophotonics are expected to be realized in the coming years. Our group is currently interested in exploiting nanophotonic enhancement of light-matter interactions as a route towards efficiently generating quantum light sources in compact form-factors, as well as for realizing ultra-compact lasers based on new gain media.

Nanophotonic scintillators: here, we demonstrated that by etching photonic crystals (periodic index modulations) on the surface of a scintillator, its light emission could be enhanced ten-fold (right two panels, showing implementation in an X-ray scintillator). Critical to the design and realization was a computationally efficient and ab initio unified framework that described the key aspects of scintillation: the underlying emitter properties (from density functional theory), the energy loss in materials by ionizing radiation, and the spontaneous emission by fluctuating currents in complex photonic structures. The key physics captured by our theoretical and simulation framework is shown on the left.

As a recent example of applications realized by nanophotonic control, see Ref. [4] and the figure above, where we used nanophotonic structures to enhance the detection of ionizing radiation (like X-rays and beta particles). Ionizing radiation is often detected using materials called scintillators, which emit light upon bombardment by the radiation. Since that radiation is dependent on the dispersion of light and the density of states, it stands to reason that by etching nanoscale patterns into scintillators, light emission can be strongly influenced.

Finally, we are interested in the applications of nanophotonic confinement for strongly enhancing “nonlinear optical” effects, and their applications for frequency conversion, metrology, and quantum state generation. See the section above on “Quantum and nonlinear optics” for more details.

References

[1] Nicholas Rivera and Ido Kaminer. “Light-matter interactions with photonic quasiparticles.” Nature Reviews Physics (2020) [Review].

[2] Nicholas Rivera*, Ido Kaminer*, Bo Zhen, John D. Joannopoulos, and Marin Soljačić. “Shrinking light to allow forbidden transitions on the atomic scale.” Science 353 6296 (2016): 263-269.

[3] Nicholas Rivera, Liang Jie Wong, John D. Joannopoulos, Marin Soljačić, and Ido Kaminer. “Light-emission based on nanophotonic vacuum forces.” Nature Physics 15.12 (2019): 1284-1289.

[4] Charles Roques-Carmes*, Nicholas Rivera*, Ali Ghorashi, Steven Kooi, Yi Yang, Zin Lin, Justin Beroz, Nicolas Romeo, John D., Joannopoulos, Ido Kaminer, Steven G. Johnson, and Marin Soljačić. “A general framework for scintillation in nanophotonics.” Science 375 6583 (2022): eabm9293.