Joshua Caldwell

Director, Interdisciplinary Program in Materials Science
Professor of Mechanical Engineering
Professor of Electrical Engineering
Professor of Chemistry

Mechanical Engineering
Electrical and Computer Engineering

Intellectual Neighborhoods

• Nano Science and Technology
• Energy and Natural Resources

Research Focus

The Caldwell lab boasts two Fourier transform infrared (FTIR) systems and attached microscopes. Both the system and microscope have been custom modified to incorporate a Sterling-cooled bolometer and a series of MCT detectors that enable measurements covering the spectral range extending from 10-10,000 cm-1 (1,000 – 1 mm). The system can perform static or time-domain experiments and work in emission mode, quantifying thermal emission, luminescence or fluorescence in the infrared from micron scale areas of interest. The lab also houses a state-of-the-art ultrafast pump-probe scattering-type scanning near-field optical microscope and nano-FTIR system. This tool can 1) spatially map the infrared absorption and reflectivity of materials at a fixed frequency with sub-20-nm spatial resolution, 2) measuring the infrared absorption and reflection spectra with the same spatial resolution, and 3) monitor the temporal evolution of the nano-FTIR spectra with 200-fs resolution following either an ultraviolet (390 nm) or near-infrared (1560 nm) ultrafast (130 fs) pump pulse. The lab has expertise in the exfoliation and transfer of two-dimensional materials and heterostructures and has assisted in the development of the VINSE transfer tool for this purpose.

Biography

Dr. Caldwell obtained his B.A. in Chemistry in 2000 from Virginia Tech with a minor in History. Following this, he attended the University of Florida where he received his Ph.D. in Physical Chemistry in 2004. He accepted an American Society of Engineering Education Postdoctoral Fellowship to the US Naval Research Laboratory in 2005, where he was hired on as a staff scientist in 2007. He was promoted to a supervisory role in 2012. In 2013-2014 Dr. Caldwell worked with Prof. Kostya Novoselov at the University of Manchester during a Sabbatical, where they studied two-dimensional materials for infrared nanophotonics, identifying hexagonal boron nitride as a natural hyperbolic material. During his time at NRL he was the recipient of three highly competitive NanoScience Institute (NSI) Grants and several awards for his published works. In 2017 he accepted a tenured Associate Professorship in the Mechanical Engineering Department at Vanderbilt University, with courtesy appointments in Electrical Engineering and Chemistry. He was promoted to Full Professor in 2022.

His research focuses on the confinement of electromagnetic energy to the nano- to atomic-scale and the interactions between light and matter within such confined systems. This involves the sub-diffractional confinement of light using 'polaritons' within the optical spectral domain (primarily the infrared), the design of nanoscale optical components, and identifying and characterizing novel optical, electro-optical and electronic materials.