Abstract

Our previous high-temperature surface electromagnetic wave (SEW) studies¹ using grating couplers, which led to the discovery of a cogenerated free space radiation (FSR) component to the detected signal and subsequent determination of ω_p for tungsten at 10 µm, demonstrated the sensitivity of SEW interference spectroscopy to this parameter. However, the technique is limited by the need to use ultrahigh vacuum to maintain a clean sample at the elevated temperatures which are needed to kill off the SEWs and observe the weak FSR component scattered from the output coupler. We are now developing a room temperature technique to measure interference between SEWs and FSR. Using aperture excitation of the surface waves and letting the edge of the metal sample act as the output coupler, we have detected interference between FSR diffracting from the aperture and SEWs coupled off the sample edge using 10-µm laser radiation. By adjusting the aperture size the FSR and SEW amplitude can be made about equal, which permits observation of the interference. Preliminary results on copper yield ω_p = 7.1 ± 0.4 eV.

© 1987 Optical Society of America