Abstract

The use of holographic components (gratings) in integrated devices is very advantageous because complex functions can be realized with a minimum number of components. Such single gratings can have various compound functions of wavefront conversion such as beam splitting, deflection, input/output coupling, focusing, and wavelength division. The grooves of these gratings are not simply straight, but curved with different curvatures and different periods. To fabricate these gratings, we have developed a specially designed EB writing system for this purpose. The system can specify 2 × 10¹⁶ computer-generated data points over a 1 mm × 1 mm area with 0.3 μm resolution. One typical example is a focusing grating coupler (FGC) for an integrated-optic disk pickup. The FGC is designed to have approximately 2,000 curved grooves over the aperture of 1 mm² and the focal length of 2 mm at a wavelength of 0.78 μm on a glass/ SiO₂/Si waveguide. Diffraction efficiency is estimated to be 60% for the optimum groove height of 35 nm. The IO disk pickup has been implemented and the fundamental functions have been experimentally confirmed. Several other grating-based waveguide devices will be discussed.

© 1992 Optical Society of America