Progress Report on (Al,Ga)As Devices for Waveguide Circuits.
Abstract
Work was concentrated on fabrication and characterization of (Al,Ga)As waveguides, developing electrooptic pads on (Al,Ga)As for active waveguide devices, and investigating laser-waveguide coupling by evanescent fields. The waveguide structures investigated have been the dielectric stripline and the rib waveguide. For straight sections of dielectric striplines we have measured attenuation losses as low as 5.3 dB/cm, and for rib waveguides, the lowest loss is 8 dB/cm. Additional radiation losses are observed in curved sections of these waveguides. The most significant parameter influencing the bending losses is the thickness of the waveguiding layer. Devices fabricated with very thin (approximately 0.5 micrometers) layers had transmission as high as 60% to 70% around a 90 deg bend having a 120 mil radius of curvature. Smaller radii result in higher loss. In developing electrooptic pads on (Al,Ga)As a problem with interfacial 'oxide' layers between the Schottky barrier contacts and the semiconductor was encountered. These layers are typically an order of magnitude thicker than those on GaAs. A practical solution to this problem appears to be the formation of shallow p-n junctions by Zn diffusions or Be implants. Finally, laser-waveguide coupling by evanescent field coupling was investigated. These devices are fabricated from five- and six-layer structures by selectively etching a laser cavity on top of an underlying passive waveguide. Typically, 10% of the laser power is coupled into the waveguide and emitted into a smaller cone angle suitable for coupling to optical fibers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1976
- Accession Number
- ADA029247
Entities
People
- J. C. Campbell
- K. L. Lawley
Organizations
- Texas Instruments