GaAs Waveguide Microlenses and Lens Arrays with Applications to Data Processing and Computing*

Abstract

Waveguide lenses are among the essential components in construction of integrated optic modules or circuits for data processing and computing. For this purpose, various types of waveguide lens have been fabricated in LiNbO3 substrate. These lens types include Luneburg, geodesic, index refraction via TIPE or two layers construction, chirp grating, and Fresnel. Some of these lens types have been utilized to construct RF spectrum analyzers, correlators,(1,2,3) and computers.(4,5,6) Despite the various successes with such LiNbO3-based modules they have only been developed into hybrid integrated optic (IO) modules due to lack of technology for integration of lasers, detectors, and associated electronic circuits in the same substrate. In contrast, the GaAs-based substrate provides the capability for monolithic integration of all passive and active components. However, the material constraints such as a very high refractive index and high brittleness, and the relatively small reduction in refractive index in Ga1−xAlxAs for a desirable fractional composition x have prevented any lens type from being fabricated in GaAs waveguide heretofore. We have most recently utilized ion-milling technique to fabricate waveguide lenses of high efficiency and diffraction-limited focal spot size in GaAs. In this paper, design, fabrication, and measured performances of single microlenses and microlens arrays of the analog Fresnel and chirp grating types as well as hybrid combination of the two are presented. IO modules that incorporate such waveguide lenses and acoustooptic and electrooptic Bragg modulators in channel-planar composite waveguides are also being constructed. The measured performances of such modules with applications to data processing and computing will also be reported.