Self-Imaging by Phase Coincidences in Rectangular Dielectric Waveguides

The imaging properties of multimode dielectric waveguides of rectangular cross-section, having a homogeneous refractive index nf are investigated theoretically and experimentally. Two-dimensional self-images are formed by the phase coincidences of a large number of modes if the effective cross-section of the guide, including the penetration depths into the cladding, is a perfect square (side Wa). The first sinqle self-image is observed at the fundamental self-imaging distance L1=4nfW2 a/¿0, where ¿O is the vacuum wavelength. The theoretical linear resolution is approximately 1.5 ¿m for a guide of Wa¿44 ¿m. Experimentally, this resolution has not quite been reached contrary to the case of slab guides, but improved results are expected.