Integrated Optics Polarized Light and Evanescent Wave Surface-Enhanced Raman Scattering to detect ligand Interactions at nanoparticle surfaces

The orientation of sensing molecules on the surface of biosensors is crucial for effective interaction with target analytes, and Raman spectroscopy is a versatile and non-invasive technique used to study molecular configurations at the sub-nanoscale level. This study explores the sensing abilities of an integrated optics construct called an Optical Chemical Bench (OCB) for the detection of molecular orientation, ion binding, and nanoparticle binding. The OCB consists of plasmonic gold-silver nanoparticles bound to the surface of a multimode slab waveguide. This design offers controlled plasmonic excitation in both position and polarization, increasing the interfacial mean square electric field relative to the incident field, and allowing for polarization-dependent surface-enhanced Raman scattering (SERS) on a chip. The experiments gave insight into how the TE and TM polarization modes interact with adsorbates that are built up as hierarchical structures on the OCB, providing an inexpensive yet effective molecular probing technology at the interface.