Geodesic Lens Performance Characteristics

The position of the focal plane, the intensity profile of the first diffraction spot and power losses have been measured for geodesic lenses in Ti-indiffused LiNb03 waveguides. It was intended for the focal plane of a geodesic lens to be situated at a waveguide edge; experimental results have shown that this was achieved to a tolerance of better than 12 im with two of the measured focal planes coinciding with the waveguide edge to within the +2 Inn accuracy of the measurement techniaue. Scans of the intensity profiles of focused diffraction spots have been made for one and two lens systems; the spot sizes in both cases were found to be <1.15 times the diffraction limit at F/12. Throughput losses in geodesic lenses ranged from 2.5 to 17 dB - the larger losses occurring in lenses with small edge rounding and large corrected regions. An analytical program was initiated to determine the various mechanisms responsible for power loss. A simplified model indicates that a significant loss is due to mode mismatch in the vicinity of the edge rounding.