Far-infrared guided wave optics experiments with anisotropic crystal quartz waveguides

The TE and TM modes of anisotropic dielectric waveguides of crystal quartz have been studied in the far infrared using an optically pumped waveguide laser with a hybrid output mirror. Using Si and Ge prism couplers, excitation efficiencies of 56 percent of the theoretically calculated values were obtained for the TE
0
mode. The measured propagation constants were found to agree closely with theory when the perturbation of the guided modes by the prism couplers was included. The attenuation constant for the TE
0
mode at
\lambda_{0} = 496.1\mu
m was found to be as low as
\alpha_{TE_{0}} = 0.05
cm
^-1
. A metal grating coupler for backward-wave coupling through a prism shaped TPX plastic substrate was also used to couple 89 percent of the guided energy in the TE
0
mode out of the waveguide in the reverse direction.