LONG-WAVELENGTH RIDGE-WAVE-GUIDE LASERS WITH PROCESSED FACETS AND INTEGRATED BACK-FACET MONITORS

InP-InGaAs cleaved-cavity lasers are routinely used in long-wavelength optical transmission systems, packaged with a discrete pin photodiode back-facet monitor used to provide feedback to control the laser outp ut power. This conventionally requires two separate wafer-fabrication processes, and individual testing, cleaving, and assembly at the chip level. The handling of cleaved bars, facet-coating, testing, and mount ing is labour-intensive and expensive. Etching mirror facets during wa fer processing makes it possible in a single fabrication process to fa bricate lasers with an integrated back facet monitor, and do on-wafer testing without further alignment and assembly. This has now been achi eved with the following technologies: (i) laser epitaxial layers used for light detection as well as emission, (ii) reactive-ion-etched (RIE ) (CH4-Ar)-etched mirror facets, and (iii) electrical interconnects by metal airbridges. Integrated laser and (or) monitors with RIE-process ed facets have threshold currents as low as 30 mA, efficiencies of 0. 14 mW mA-1, and monitor efficiencies of 0. 1 mA, mW-1. Excellent unifo rmity was observed across a 2 in (1 in = 2.54 cm) wafer. The lower thr eshold currents (27 mA) observed for cleaved facet lasers from the sam e wafer indicate that the processed facet quality can be further impro ved; the optimum RIE process results in etched facets with a facet ang le about 5-degrees off vertical. Packaged devices have been successful ly operated at speeds up to 1 Gb s-1 for both laser and monitor. Preli minary reliability studies are described.