Sensitivity Enhancement of Magneto-Optical Surface Plasmon Resonance (MOSPR) Biosensor

We present the optimization of a new material structure used as transducer in a MagnetoOptical Surface Plasmon Resonance (MOSPR) biosensor. The MOSPR sensor is a modification of the standard Surface Plasmon Resonance (SPR) biosensor, which arises from the introduction of a ferromagnetic metal layer with Magneto-Optical (MO) activity together with the usual gold layer of SPR biosensors. Such combination generates a very intense Transversal Magneto-Optical Kerr Effect (TMOKE) when the SPR is excited. Similarly to the SPR, the TMOKE signal of the magnetoplasmonic transducer strongly depends on the refractive index of the external dielectric medium (next), providing the sensing principle. The optimized design of the magneto-plasmonic transducer can induce a higher sensitivity to the changes in next in the MOSPR signal as compared to the signal of conventional SPR sensors (the reflectivity of the p-polarized light). Although the MOSPR biosensor has proved to be two times more sensitive than a conventional SPR biosensor, further optimizations can lead to a limit of detection improvement up to one order of magnitude. In addition, as the MOSPR multilayer transducer also ends in a gold surface, the biofunctionalization of the receptor layer can be done using the well-known thiol-based immobilization protocols developed for standard SPR sensors. These features turn the MOSPR biosensor into a simple solution to improve the current detection limits of plasmonic biosensors, which is needed for highly sensitive applications.