Consequences of Cavity Length Non-Uniformity on Optical Spectroscopy in Strong-Coupling Experiments

Reports of modified materials processes under vibrational strong coupling (VSC), which include cavity-mediated vibrational energy transfer, modified chemical product selectivity, and altered solvent-solute interaction forces, have been met with a great deal of skepticism due to several irreproducible results and the lack of an accepted theoretical framework. In this work, we add some insight by identifying an optical measurement artifact arising when a distribution of cavity lengths is probed. This artifact can alter extracted chemical reaction rates and, therefore, has important implications for numerous previously reported, and contested, examples of cavity-modified chemistry. We then use these revelations to inform best practices for carrying out reliable measurements in cavities.