ASOC/sup TM/-a silicon-based integrated optical manufacturing technology

ASOC/sup TM/ technology is based on single-mode rib waveguides formed on silicon-on-insulator wafers. Silicon waveguides have excellent properties for many applications in the 1.3 and 1.55 micron telecommunications bands that include, for example, low loss (<02 dB/cm) and relatively small birefringence (<10/sup -3/). The high refractive index of silicon (3.5) allows compact optical circuits to be made, and schemes for reducing waveguide bend radius further will be discussed. This technology was developed by Bookham to overcome the high costs of optical components for use in optical networks, creating a device technology designed for volume manufacturing. It is based on the same processing techniques used in the manufacture of conventional silicon chips, with the addition of integrated optics design and micro-machining techniques for the mechanical assembly features. An important aspect of ASOC/sup TM/ is the incorporation of discrete lasers and photodetectors to form hybrid devices. Laser chips are located in etched features in the silicon, so that the laser stripe is readily aligned with the optical waveguide. Photodiodes are mounted over waveguide mirror structures. In both cases the active element is attached to the silicon by a solder process. Bookham's products are based on a set of integrated optics elements that can be put together to form a number of practical integrated optics devices. The basic elements include bends, couplers and fiber-waveguide interfaces. More sophisticated waveguide elements that have been developed include free-carrier modulators and waveguide gratings.