A Measurement of Evanescent Fields Generating on Metal Thin Films and Langmuir-Blodgett Ultrathin Films

Surface plasmons (SPs) were resonantly excited for aluminum (Al) thin films and arachidate acid (C20) LB ultrathin films on the substrates in a Kretschmann configuration of the attenuated total reflection (ATR) method. Evanescent fields generating on the Al thin films and the LB films due to excitations of the SPs were detected as luminescent light from a metallic needle probe covered with CdS in the localized evanescent fields. The luminescent light, that is, the evanescent fields were measured as a function of the incident angle of the laser beam exciting the SPs and as a function of the distance from the surface. The luminescent light intensity was biggest at a lower angle than the resonant angle. These properties were calculated and discussed. Evanescent fields were also measured for C20 LB films on Al thin films.