Gerhard Luz

High sensitivity InP-based monolithically integrated pin-HEMT receiver-OEIC's for 10 Gb/s

InP-based pin-HEMT receiver-OEICs with different circuit layouts for bit rates up to 10 Gb/s are simulated, realized and characterized. The circuits under investigation are a high impedance amplifier, a common-gate circuit, and a transimpedance-cascode circuit. The high frequency behavior of all circuits is compared by means of on-wafer characterization. All circuits show a bandwidth of more than 5 GHz, the transimpedance circuit has the highest responsivity (12.9 dB A/W) and a very low average noise current of 11.5 pA//spl radic/(Hz) when assembled in a module. The receiver sensitivity of the transimpedance circuit in the module is measured to be as high as -19.2 dBm. >

Laser beam joining of optical fibers in silicon V-grooves

The increasing use of optical data transmission systems and the development of new optical components require adjustment-insensitive and reliable joining and assembling techniques. The state of the art includes the utilization of silicon submounts with anisotropically etched V-grooves. Several glass fibers are fixed in these V-grooves with adhesive. Adhesive bonds tend towards degradation under the influence of temperature and moisture. For this reason, the alternative joining processes laser beam welding and laser beam soldering are relevant. The goal is a reliable joining of optical fibers in V-grooves without damage to the fibers or the silicon submount. Because of the anomaly of silicon during phase transformation, a positive joining can be realized by laser beam welding. A melt pool is created through the energy of a Nd:YAG-laser pulse. During solidification, the volume of silicon increases and a bump is formed in the center. Experiments have shown that this phenomenon can be used for joining optical fibers in silicon-V-grooves. With suitable parameters the silicon flows half around the fiber during solidification. For each fiber, several welding points are necessary. Another promising joining method is laser bema soldering. In this case, a second silicon sheet with a solder deposit is placed on the fibers which lie in the V-grooves of the metallized silicon submount. The laser heats the upper silicon until the solder metals by heat conduction.