Investigation of As2S3 optical fibers for devices used to match planar and cylindrical waveguides

The spectral transmission of As₂S₃ fibers was investigated in the wavelength range 0.7–12 μ. It was found to be possible (by using circular illumination) to produce a complex refractive-index distribution profile over the fiber cross section. A theoretical analysis was made of the efficiency of matching optical fibers to planar waveguides, using the optical tunneling effect. An experimental investigation was then made of the efficiency of coupling radiation into a planar waveguide, and of the dependence of the selective excitation of the waveguide modes on the excitation conditions of the fiber-optic waveguide. A method was developed for enabling the efficiency of coupling radiation into a waveguide to be increased for fibers of small diameter having only a few modes. The efficiency of coupling radiation into the waveguide was 15%.