Plasmonic and magnetoplasmonic interferometry for sensing

The use of plasmonic and magnetoplasmonic interferometers as refractometric-based sensors is studied theoretically, and their performance compared to that of the most commonly used plasmonic sensing technique, the surface plasmon resonance (SPR) sensor. The analysis is based on the evolution with the refractive index of the physical parameters involved for each kind of sensor, as well as the behaviour of the actual measured quantity. Two kinds of sensing configurations, two-dimensional surface and three-dimensional bulk, are considered, and the spectral dependence of the three systems is also taken into account. We show that, although the plasmonic interferometer and the SPR system are based on the same physical parameter, namely the surface plasmon polariton (SPP) wavevector, the first offers better properties as its final sensitivity depends on the interferometer size and can thus be increased by its enlargement. For the magnetoplasmonic interferometer, on the other hand, a new physical parameter participates-the modulation of the SPP wavevector induced by an external applied magnetic field. This new parameter has a higher sensitivity to the refractive index than the SPP wavevector, so monitoring it can lead to sensors with increased properties.