Otto Voegeli

Full-wafer technology-A new approach to large-scale laser fabrication and integration

A new concept for full-wafer processing and test- ing for semiconductor laser fabrication in the AIGaAs-GaAs material system will be presented. The approach is based on chemically assisted ion beam etching for the laser-mirror for- mation. The technique routinely provides excellent mirror quality with mirror roughness of less than 200 A, resulting in mirror reflectivities of about 30% and scattering losses of less than 2%. Lasers with two etched mirrors have been fabricated that show equivalent output powerlcurrent (P/I) characteris- tics to lasers on the same wafer with both mirrors cleaved, up to more than 40 mW (CW) for uncoated mirrors. Single-mode operation exceeding 50 mW output power has been achieved for an SQW-GRINSCH ridge laser structure with coated, etched mirrors. Furthermore, the etching technique has been used to fabri- cate special devices and structures for on-wafer parametric laser and beam property characterization. This new approach to full-wafer testing allows efficient on-wafer functional testing of a large number of lasers on a 2-in wafer, with considerable improvement in testing throughput. The concept also incorpo- rates many test sites for process characterization which provide important feedback for process improvement/optimization. In addition to the above advantages of full-wafer processing and testing, the availability of high-quality etched mirrors will pro- vide the potential for lasers with specially shaped mirrors, and will open up new opportunities for opto-electronic integration. The approach described has been developed for lasers to be used in optical storage at wavelengths of 830 and 856 nm. How- ever, the basic concept can be applied to semiconductor laser fabrication in any other material system and wavelength range. The major difference will be the adaptation of the mirror-etch- ing process to the composition of the material.

The use of bubble lattices for information storage

A new approach to bubble memories, called a bubble lattice file (BLF), is described. This approach employs a periodic bubble lattice to define bit positions while the information is contained in the wall structure of the bubbles. The principal advantage of the BLF is the increased storage density, sixteenfold when the resolution capability of the fabrication process is the limiting factor. The device functions required for the BLF, including accessing and write/read operation, are described. Significant differences between BLF and the T‐I bar bubble memories are discussed.

Beam properties of AlGaAs power lasers with high-quality etched mirrors

High-quality etched mirrors for AlGaAs/GaAs power lasers for applications in optical storage have been fabricated by chemically assisted ion-beam etching (CAIBE). In order to ensure flat mirror facets of the ridge-waveguide lasers, a flared-waveguide end section is used. This results in a very slight mirror roughness of approximately 20 nm across the beam cross section, and yields excellent beam properties allowing diffraction-limited focusing up to 50-mW output power.<<ETX>>

Mirror fabrication for full-wafer laser technology

The fabrication of etched mirrors for AlGaAs semiconductor lasers is described. The coating techniques for the passivation and reflectivity modification of the etched mirror surfaces are presented. Measurements on coated lasers show excellent beam quality, and satisfactory uniformity of laser characteristics across a wafer. Lasers which operate in a single transverse mode at output powers up to about 50 mW and have catastrophic optical damage (COD) thresholds greater than 120 mW have also been demonstrated.