Topology optimization of surface-enhanced Raman scattering substrates

Abstract

Surface-enhanced Raman spectroscopy is a powerful and versatile sensing method with a detection limit down to the single molecule level. In this article, we demonstrate how topology optimization (TopOpt) can be used for designing surface enhanced Raman scattering (SERS) substrates adhering to realistic fabrication constraints. As an example, we experimentally demonstrated a SERS enhancement factor of 5 × 10 4 for the 604 cm -1 Raman line of rhodamine 6G using metal nanostructures with a critical dimension of 20 nm. We then show that, by relaxing the fabrication constraints, TopOpt may be used to design SERS substrates with orders of magnitude larger enhancement factor. The results validate topology optimization as an effective method for engineering nanostructures with optimal performance and fabrication tolerance.

Inverse-Designed Lithium Niobate Nanophotonics

“…Importantly, all simulations are performed in 3D, taking fully into account the practical rib/slab thicknesses, crystal anisotropy, and sidewall angles, which are crucial to realize experimentally achievable designs. More mathematical details regarding the inverse design algorithms can be found in the device design section and Figure S1 in the SI, as well as in previous references. ,, Figure c–e shows schematic views of the designed structures and their corresponding functions of our mode multiplexer, waveguide crossing, and compact waveguide bend, respectively.…”

“…More mathematical details regarding the inverse design algorithms can be found in the device design section and Figure S1 in the SI, as well as in previous references. 38,39,47 volume data transmission systems. 48 In our design, the fundamental TE 0 mode in a 2 μm wide input waveguide will be coupled into the upper output arm, whereas the TE 1 mode will be converted into TE 0 mode, and output from the bottom arm (Figure 2a).…”

“…Moreover, dry-etched LNOI waveguides usually exhibit a substantial sidewall angle, which needs to be taken into consideration during the optimization process to achieve accurate modeling and which also limits the minimally achievable feature sizes. More recently, inverse-design algorithms that take into account specific geometric constraints and sidewall angles have led to designs and demonstrations compatible with standard foundry services and in more exotic material platforms such as diamond and silicon carbide . However, the realization of inverse-designed LNOI devices is still missing and could substantially benefit the development of compact LNOI photonic integrated circuits, especially when dealing with complex design problems with multiple objective figures of merit.…”

Trace formulation for photonic inverse design with incoherent sources

“…We are already preparing to use these techniques to optimize Raman sensing in fluid suspensions of many Raman molecules, in contrast to previous work that only considered a single-molecule location (Christiansen et al 2020;Pan et al 2021)-it will help us to answer the interesting open question of the optimal spatial density of "hot spots" where light is concentrated to enhance Raman emission. Another application is enhancing cathodoluminescence or other forms of scintillation detectors, which were previously optimized only for normal emission (Roques-Carmes et al 2021).…”

Genetic Algorithm-Driven Surface-Enhanced Raman Spectroscopy Substrate Optimization

“…As a result of these analyses, it was seen that the optimization of SERS substrates with the GA allowed a SERS system design with a comparable performance to the current SERS substrates and in which the distribution of hot-spots on the surface could be controlled. The experimental EF was calculated with the method used in the previous studies [10,[34][35][36][37]. The EF was calculated using the following equation:…”