Research

Thermal radiation and Renewable energy

Can we generate renewable energy by pointing a semiconductor cell at the sky? How about at night? Yes, and yes! The clear, cold night sky is a vast, unrealized renewable energy resource. Our research explores the fundamental, thermodynamic limits of renewable energy extraction from the cold night sky.

The second law of thermodynamics prescribes that in passive, time-independent systems, heat must flow from hot to cold. But what about time-dependent systems? We show that a time-varying refractive index enables a "photonic" refrigerator, allowing a cold object to pump heat towards a hot object. Check out our PRL and popular science coverage!

High-school physics taught us that thermal radiation from any hot object is capped by the Stefan-Boltzmann law. But this is true only in the "far-field", where hot objects are far away from each other - like the Sun and Earth. When hot objects are sufficiently close to each other, or in the "near-field", the Stefan-Boltzmann law can be overcome by orders of magnitude! This can enable future renewable energy technologies such as thermal photovoltaics (TPVs) with high efficiency and power density.

Time-Dependent photonic systems

The second law of thermodynamics prescribes that in passive, time-independent systems, heat must flow from hot to cold. But what about time-dependent systems? We show that a time-varying refractive index enables a "photonic" refrigerator, allowing a cold object to pump heat towards a hot object. Check out our PRL and popular science coverage!

optical metamaterials

Metamaterials are artificial materials that exhibit new behaviors not found in natural materials. Over the years, dozens of strange and exciting properties have been discovered in these artificial materials. Here, we ask: is it possible to construct an artificial material that breaks Lorentz reciprocity while still effectively appearing to be time-reversal symmetric? What cool properties would such a material have?

plasmonics

Plasmonics is the study of hybrid electron-light oscillations at metallic interfaces. These oscillations can have wavelengths much, much smaller than the wavelength of light at the same frequency. Here, we consider a peculiar problem: what happens when a plasmonic system breaks Lorentz reciprocity? It turns out that quantum mechanical effects become very important, and ignoring them can lead to thermodynamic paradoxes!

solid-state high-harmonic generation

nanoelectronics