Skyler P. Selvin | Searcharxiv

arXiv2026

RF heating-enhanced photoacoustic tomography

Photoacoustic tomography (PAT) and thermoacoustic tomography (TAT) both leverage acoustic signals generated by electromagnetic absorption to noninvasively image deep tissues. PAT operates by detecting optical absorption, whereas TAT targets radiofrequency (RF) absorption, providing complementary information on tissue composition and structure. Combining these modalities into a single system promises richer contrast but remains difficult due to the expense and complexity of the RF source. Here, we show that PAT can be integrated with a low-cost RF heater and used to image both optical and RF absorption in tissue phantoms. RF Heating-Enhanced Photoacoustic Tomography (HEPAT) maps RF absorption via temperature-dependent changes in thermomechanical properties, which enables the use of slow, inexpensive RF subsystems and provides an additional layer of contrast. HEPAT therefore provides distinct, complementary contrast relative to existing photoacoustic imaging systems, expanding specificity and diagnostic power while opening new avenues for studying temperature-related tissue phenomena.

physics.optics↗

arXiv2025

Acoustic wave modulation of gap plasmon cavities

The role of metallic nanostructures in nanophotonics is expected to expand if ways to electrically manipulate their optical resonances at high speed can be identified. Here, we capitalize on electrically-driven surface acoustic waves and the extreme light concentration afforded by gap plasmons to achieve this goal. We place gold nanoparticles in a particle-on-mirror configuration with a few-nanometer-thick, compressible polymer spacer. Surface acoustic waves are then used to tune light scattering at speeds approaching the GHz regime. We observe evidence that the surface acoustic waves produce mechanical deformations in the polymer, and that ensuing nonlinear mechanical dynamics lead to unexpectedly large levels of strain and spectral tuning. Our approach provides a design strategy for electrically driven dynamic metasurfaces and fundamental explorations of high-frequency, polymer dynamics in ultra-confined geometries.

physics.optics↗