UV Spectroscopy Team at USU
Uncovering new behaviors and validating novel models of electron and phonon transport in nanoscale geometries using a suite of unique spectroscopies based on coherent ultrafast, ultraviolet light pulses.
Research Overview
To develop next-generation computer chips, faster communication devices, robust solid-state batteries, and quantum computers, we desperately need a better understanding of how energy—in the form of heat, electricity, or magnetic interactions—flows through materials over ultra-small scales. Today’s transistors that power our electronic devices have dimensions much smaller than the thickness of a human red-blood cell and can generate heat fluxes greater than the surface of the sun! [1] However, our theoretical calculations cannot predict this intense behavior and our traditional tools cannot probe the physics.
In the UV Spectroscopy lab at USU, we build novel and cutting-edge measurement techniques that harness ultraviolet lasers. By using ultrafast infrared lasers, we can drive nonlinear processes to create laser-like light at wavelengths that is traditionally inaccessible. These ultraviolet spectroscopy tools can observe energy flow at incredible length- and time-scales: we can ‘see’ physics at the intersection of the ultra-small (nanometers) and ultra-fast (femtoseconds) scales. We use these unique tools to test new models of the energy flow and condensed matter physics, along with characterizing the properties of future materials. In recent work, we measured phonons—quantized vibrations of a solid which carry heat—traveling through nanoscale constrictions allowing us to build new models of energy carrier dynamics and reveal new understanding of exotic energy transport behavior.
​​​Our research group studies condensed matter and material physics using novel tools that harness advances in nonlinear, quantum, and optical physics. We perform cross-cutting research that is both fundamental with near-future applications in fields including mechanical, electrical, aerospace, and materials engineering.​
[1] Warzoha et al. Applications and Impacts of Nanoscale Thermal Transport in Electronics Packaging. Journal of Electronic Packaging, Transactions of the ASME 2021, 143 (2), 020804.
Latest Publications
Tabletop deep-ultraviolet transient grating for ultrafast, nanoscale carrier-transport measurements in ultrawide-band-gap materials
E. E. Nelson, B. McBennett, T. H. Culman, A. Beardo, H. C. Kapteyn, M. H. Frey, M. R. Atkinson,
M. M. Murnane, and J. L. Knobloch
Understanding nanoscale electron and phonon transport is critical for the development of next-generation semiconductor technologies, where deviations from macroscopic behaviors can either limit or enhance device performance. While transient gratings generated by the interference of visible lasers can directly excite microscopic, nonequilibrium charge and heat distributions in metals and traditional semiconductors, extending this noncontact approach to ultrawide-bandgap materials involves added complexities. To address these challenges, here we introduce a tabletop deep-ultraviolet (DUV; 6.3 eV) transient grating setup, and show that it supports sub-300 nm spatial and subpicosecond temporal resolution. As an initial demonstration, we excite and probe gigahertz surface acoustic waves in thin gold films. We then perform DUV transient grating measurements of nanoscale carrier transport in diamond and discuss the carrier concentration-dependent diffusion coefficient. This DUV transient grating capability provides a versatile, noncontact tool for investigating transport at length scales below the visible diffraction limit and in wide-bandgap materials, and bridges the gap between visible and facility-scale extreme-ultraviolet transient grating capabilities.
Phys. Rev. Applied 2024, 22, 054007
Schematic of the deep-ultraviolet transient grating spectroscopy experiment. An ultrafast infrared laser is upconverted to the deep-ultraviolet (DUV) via sum-frequency generation in a nonlinear BBO crystal. The DUV is split and recombined via a diffraction grating and 4-f lens system. The interference of the two DUV beams creates a sinusoidal temperature profile which excites dynamics in the sample at a set lengthscale. The short-wavelength of the DUV light allows for direct excitation of ultrawide-band-gap materials and to probe dynamics on the 100s of nanometer scale. Image copyright of the American Physical Society. Work performed at previous institution, JILA - University of Colorado Boulder
