Fe thicknesses dependence of attenuated total reflection response in magnetoplasmonic double dielectric structures: angular versus wavelength interrogation

Al2O3/SiO2/Fe/Au structures with different Fe thicknesses were fabricated using different deposition techniques. Due to the cutoff condition of surface plasmon polaritons in the double-layer dielectric structure and magneto-optical effect, the reflectivity spectra show a minimum and its angular and wavelength positions can be modulated by the magnetic field. For thin Fe layers, the magnetic field modulates mainly the angular position, whereas for thick Fe layers both wavelength and angular positions are modulated. The proposed structure and the angular and wavelength dependence suggest two feasibilities of (1) two selectable interrogation modes: whereas for structures with thin Fe layers angular interrogation mode is preferred, with thick Fe layers wavelength interrogation mode is more appropriate, and (2) discrimination of analyte in the complex space: the refractive shift in the real part would dominantly appear in the angular interrogation, while the imaginary part in the wavelength interrogation.