Plasmonic Optical Sensors: Performance Analysis and Engineering Towards Biosensing

Surface plasmon resonance (SPR) sensing for quantitative analysis of chemical reactions and biological interactions has become one of the most promising applications of plasmonics. This thesis focuses on performance analysis for plasmonic sensors and implementation of plamonic optical sensors with novel nanofabrication techniques. A universal performance analysis model is established for general two-dimensional plasmonic sensors. This model is based on the fundamental facts of surface plasmon theory. The sensitivity only depends on excitation light wavelength as well as dielectric properties of metal and dielectrics. The expression involves no structure-specified parameters, which validates this formula in broad cases of periodic, quasiperiodic and aperiodic nanostructures. Further analysis reveals the intrinsic relationship between plamonic sensor performance and essential physics of surface plasmon. The analytical results are compared to the sensitivities of previously reported plasmonic sensors in the field. This universal model is a promising qualification criterion for plasmonic sensors. Plasmonic optical sensors are engineered into high-performance on-chip sensors, plasmonic optical fibers and freestanding nanomembranes. (1) Periodic nanohole arrays are patterned on chip by a simple and robust template-transfer approach. A spectral analysis approach is also developed for improving the sensor performance. This sensor is applied to demonstrate the on-chip detection of cardiac troponin-I. (2) Plasmonic optical fibers are constructed by transferring periodic metal nanostructures from patterned templates onto endfaces of optical fibers using an epoxy adhesive. Patterned metal structures are generally extended from nanohole arrays to nanoslit arrays. A special plasmonic fiber is designed to simultaneously implement multimode refractive index sensing with remarkably narrow linewidth and high figure of merit. A real-time immunoassay relying on plasmonic fiber is demonstrated. Plasmonic optical fibers also take advantages of consistent optical responses, excellent stability during fiber bending and capability of spectrum filtering. (3) Large-area freestanding metal nanomembranes are implemented using a novel fabrication approach. The formed transferrable membranes feature high-quality and uniform periodic nanohole arrays. The freestanding nanomembranes exhibit remarkably higher transmission intensity in comparison to the nanohole arrays with same features on the substrate. These three modalities of plasmonic sensors possess different applicability to fulfill various plasmonic sensing tasks in respective scenarios