Infrared surface wave heterodyning on metals and semiconductors

Abstract

Surface electromagnetic waves (SEW) due to their unique fielddistribution (field maximum occurs at the two adjacent mediainterface) is a highly sensitive instrument for studying both metalsurfaces and thin films on them. The experimentally measurableparameters in SEW experiments are the SEW propagation distance L(14=1/4m)n—) and the real part of SEW refraction index n'ef efC C i/2i 2)). For metals in middle and far infrared region y,ef C +ci 2u01..) (p , - - plasmon frequency and damping constant) n' is directlyP p efdetermined by plasma frequency. Therefore, the difference between thelight line k =())/c and the surface polariton dispersion curve0k =w/chi is insignificant and in such circumstances the measurement$p efof n' is problematic. Usually it is measured by scanningefinterference pattern of bulk radiation with SEW launched on thesample edge [1]. In the FIR region SEW propagation distance on metalsis too large (a few meters) and transparent films are sputtered on ametal surface with the purpose to press SEW field to the surface [2].For SEW phase spectroscopy in doped semiconductors additional is filmnot requires [3]. Another method, proposed in [4], is based on SEWheterodyning and was realized on gold and copper at CO -laser2frequencies.