Rapid theoretical method for inverse design on a tip-enhanced Raman spectroscopy (TERS) probe

Abstract

Tip-enhanced Raman spectroscopy (TERS) can provide correlated topographic and chemical information at the nanoscale, with great sensitivity and spatial resolution depending on the configuration of the TERS probe. The sensitivity of the TERS probe is largely determined by two effects: the lightning-rod effect and local surface plasmon resonance (LSPR). While 3D numerical simulations have traditionally been used to optimize the TERS probe structure by sweeping two or more parameters, this method is extremely resource-intensive, with computation times growing exponentially as the number of parameters increases. In this work, we propose an alternative rapid theoretical method that reduces computational loading while still achieving effective TERS probe optimization through the inverse design method. By applying this method to optimize a TERS probe with four free-structural parameters, we observed a nearly 1 order of magnitude improvement in enhancement factor (|E/E0|2), in contrast to a parameter sweeping 3D simulation that would take ∼7000 hours of computation. Our method, therefore, shows great promise as a useful tool for designing not only TERS probes but also other near-field optical probes and optical antennas.