On the sensitivity of surface plasmon resonance sensors with spectral interrogation

Theoretical analysis of the sensitivity of surface plasmon resonance (SPR) sensors with spectral interrogation is presented. Two basic configurations of SPR sensors with spectral interrogation are investigated—for the measurement of variations in the refractive index of bulk media, and for the monitoring of variations in the thickness of thin films. In both cases, analytical expressions allowing the sensitivity of SPR sensors to be calculated are derived and validated. On the basis of the theoretical analysis, the optimization of a spectral SPR sensor in terms of the operation wavelength and the choice of metal layer is carried out. It is demonstrated that spectral SPR sensors may attain higher sensitivity if operating at longer wavelengths and if using metal layers with a higher modulus of the real part of the dielectric constant.