<title>Diamond-Machined Geodesic Lenses In LiNbO3</title>

Abstract

The application of single point diamond turning to the fabrication of aberration-corrected, aspheric geodesic lenses in LiNb03 for use in integrated optics is reported. F/5 lenses with useful apertures of 4 mm and 5 mm have been produced. Lens profile accuracies ranging between 1.5 and 3 pm total indicator reading and depth accuracies of 0.25 to 2.0 μm have been achieved. The machined surfaces require only light polishing, which produces little effect on the figure accuracy, to remove residual machining marks. Waveguides grown by Ti-indiffusion are found to be characterized by very low scattering losses. Optical image spot sizes of 1.35 to 2.23 times diffraction-limited have been measured for input beam widths of 1.0 to 3.28 mm for a lens in which the edge rounding has not been incorporated into the aspheric correction. The edge rounding has been included in the correction for subsequent lenses.