Optical waveguiding phenomena at 10.6 µm have been observed in evaporated amorphous Se films with Au-cladding. The far-field analysis has shown that the fundamental TE0 mode is most dominantly confined. The results show that amorphous Se can be used to form planar waveguides for the 10.6 µm radiation of a CO2 laser. It has been also observed that the attenuation of TM modes is much larger than that of TE modes in accordance with the theory of the metal-clad optical waveguides. As an application, a photoelastic modulator utilizing a piezoelectric resonance of the Au-clad amorphous Se waveguide has been fabricated. The PZT piezoelectric ceramics is used as the substrate to excite mechanical vibration. The modulator is operated around its fundamental length-expanding resonance of 211.2 kHz. The band-width and the half-wave voltage are determined to be 5.4 kHz and 55 V, respectively.