Sensitivity comparison of surface plasmon resonance (SPR) and magneto-optic SPR biosensors

Abstract

Sensitivity of a biosensor is one of the most important parameters that determines its performance. It depends on many factors, such as excitation wavelength of incident optical radiation (\( \lambda\) , composition, type, and thickness of the ferromagnetic Co layer ( \( t_{\rm Co}\) , plasmonic Au, and high refractory metal, Ti, involved, and sensing/excitation configuration. In this paper, both the surface plasmon resonance (SPR at the magnetic field, H = 0 and magneto-optic SPR (MOSPR at H sensitivity of the sensors have been theoretically calculated in the visible wavelength regime using air-helium media as probing samples in the Kretschmann configuration, and their performances are compared side by side. The calculated MOSPR sensitivity of \( 1.25 \times 10^5\%\) /RIU (refractive index unit) at \( \lambda = 632.8\) nm is almost 12.5× larger as compared to the SPR sensitivity of \( 1.0 \times 10^4\%\) /RIU for the same geometry, excitation condition, and probing media. Likewise, the MOSPR sensitivity of \( 1.25 \times 10^5\%\) /RIU at \( \lambda\) = 632.8 nm is almost 10× larger as compared to the MOSPR sensitivity of \( 1.25 \times 10^4\%\) /RIU at \( \lambda\) = 515 nm for the same geometry and probing media. On decreasing the \( t_{\rm Co}\) , the sensitivity of the MOSPR sensor is further increased by almost 3× , from \( 1.25 \times 10^5\%\) /RIU at \( t_{\rm Co} = 8\) nm to \( 3.7 \times 10^5\%\) /RIU at \( t_{\rm Co} = 4\) nm. The sensitivity can be further improved by additional optimization of the material used and sensor configuration employed for detection.