Thomas Folland
University of Iowa, IA·Physics·Early-career
Everything near room temperature glows faintly in long-wavelength infrared light, and many gases leave a distinctive fingerprint there, so this part of the spectrum is where thermal cameras and chemical sensors operate. The trouble is that infrared photons carry very little energy, so the semiconductors that detect them are easily swamped by heat-generated noise and usually need bulky cryogenic cooling.
- Fields
Physics
Materials Science
Engineering
- Topics
phonon polaritons
shear polaritons
infrared photodetectors
- Grants
- 2 known grants, through May 2028
What they work on
- Demonstrate resonant coupling between surface phonon polaritons in gallium arsenide, light waves bound to crystal lattice vibrations, and intersubband transitions in quantum well photodiodes, to enhance infrared absorption and detection beyond 8 micrometers.
- Extend phonon polariton enhancement to additional infrared wavelengths by coupling modes supported by epitaxial oxide layers grown on quantum well photodiodes to the detector's absorbing region.
- Integrate van der Waals materials, atomically thin crystals that can be mechanically transferred, onto semiconductor active regions to achieve phonon polariton enhanced detection across a wide wavelength range.
- Build a theoretical and experimental framework for how shear polaritons propagate and scatter in crystals of the lowest crystalline symmetry, where unit cells are slanted rather than rectangular.
- Demonstrate polaritonic emission from low-symmetry excitonic materials to produce asymmetric, directional photoemission with controlled linear, circular or vortex polarization in the long-wave infrared.
- Develop photonics education materials, including lesson plans built with middle-school teachers and research-style projects for junior undergraduates, distributed online for national use.
More about the research
Both projects here attack infrared light control using phonon polaritons: hybrid waves formed when light couples to the natural vibrations of atoms in a crystal. Because these waves live in undoped crystals rather than metals, they lose less energy and squeeze light into tiny volumes. One project uses them to build better infrared detectors; the other asks what new optical behavior appears in crystals with very little symmetry.
Why it matters
Long-wavelength infrared detectors today are expensive and often need cryogenic cooling, which limits where thermal imaging and gas sensing can be deployed. Detectors with crystal-vibration antennas could operate with less noise at higher temperatures, making infrared cameras for monitoring temperature, industrial processes and atmospheric chemicals cheaper and more scalable. Understanding light in low-symmetry crystals could yield compact light sources with built-in control of beam direction and polarization, cutting the need for added optics.
Known grants
From NIH and NSF research grants. Labs often have other funding we can't see.
Closest labs
Maxim Shcherbakov
University of California-Irvine, CA·Physics·Early-career
Determine the fundamental properties of photonic-phononic metasurfaces that pair resonant dielectric nanostructures with phonon-polaritonic materials such as hBN and MoO3, using full-wave simulations, nanofabrication and near-field microscopy.
Leonid Butov
University of California-San Diego, CA·Physics
Study spin transport carried by indirect excitons, electron-hole pairs split across separate semiconductor layers, using optical measurements in layered heterostructures.
Xianfan Xu
Purdue University, IN·Engineering
Develop theory for how radiative heat transport by hyperbolic phonon polaritons, light-lattice vibration waves, inside hyperbolic materials depends on wavelength and temperature.
The school
University of Iowa: 32 labs on PI Pages, $703M a year on research, 418 research doctorates a year.
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