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

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 similar to 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.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

Tip-enhanced Raman spectroscopy (TERS) provides nanoscale topographic and chemical information with high sensitivity and spatial resolution, determined by the lightning-rod effect and local surface plasmon resonance (LSPR). Traditional 3D numerical simulations for optimizing TERS probe structure are resource-intensive, but a rapid theoretical method using inverse design can achieve effective optimization while reducing computational loading. By applying this method to a TERS probe, an order of magnitude improvement in enhancement factor (|E/E0|2) was observed compared to a parameter sweeping 3D simulation that would take around 7000 hours. This method shows promise for designing TERS probes, near-field optical probes, and optical antennas.