Advanced hybrid bulk/integrated optical signal processing modules.

摘要

The research described in this thesis focuses on the advancement of novel hybrid bulk/integrated optical and optoelectronic device technology suitable for both inherently planar and inherently non-planar optical signal processing applications. Such applications include spread spectrum communications, high frequency pulse compression, wide bandwidth correlation for automatic target recognition, and synthetic aperture radar (SAR) image formation, among a wide variety of comparably complex multi-dimensional signal processing tasks. The primary focus was on the development of key components for all integrated optical synthetic aperture radar (IOSAR) processor. These components include wide aperture, short focal length embedded waveguide lenses for collimating, imaging, and Fourier-transform operations, dense rib waveguide arrays for in-plane image dissection, and surface outcoupling gratings for uniform guided-wave coupling to external components.; The above-mentioned waveguide components were fabricated on low-loss (0.42 dB/cm) planar titanium-indiffused lithium niobate (Ti:LiNbO{dollar}sb3{dollar}) waveguides. Embedded lenses were fabricated by ion-beam milling a lens-shaped recess into the planar waveguide, followed by the deposition of an SiO{dollar}sb2{dollar}/MgF{dollar}sb2{dollar} dielectric waveguide into the recess. The best lens performed at f/2, with a 1 cm focal length, a 3 dB insertion loss, and a 0.9 {dollar}mu{dollar}m spot size inside the waveguide. Rib waveguide array structures (8 {dollar}mu{dollar}m rib widths) were fabricated and the rib-to-rib coupling characteristics were measured. Large, uniform surface outcoupling gratings with 2 {dollar}mu{dollar}m and 4 {dollar}mu{dollar}m periods were fabricated on planar and rib waveguides on Ti:LiNbO{dollar}sb3{dollar} waveguides. Similar rib waveguide and grating structures were fabricated on GaAs/AlGaAs waveguides.; Embedded lenses, rib waveguide arrays, and surface acoustic wave modulators were integrated onto a common Ti:LiNbO{dollar}sb3{dollar} waveguide. Selective optical excitation of individual rib waveguides was achieved by steering a guided optical beam through the lens. The overall feasibility of the IOSAR processor was evaluated with respect to the final state of advancement of the individual components and their integration onto a common substrate.