Boosting the output power and wall-plug efficiency of lasers on a generic InP platform

Abstract

Establishing a photonic integrated circuit (PIC) process is expensive, and unreachable for most companies. The foundry model (FM), in which a small number of generic foundries (GFs) provide optimized manufacturing facilities to a great mass of fabless circuit designers, lowers the costs and makes PIC technology widely accessible. The downside of GF platforms is the fixed process flow, which limits the design freedom on the physical level. Thus, the PIC performance has to be tweaked and optimized on a circuit level. In this work, we optimize the output power of a laser by circuit level design only. Two methods are investigated experimentally. Firstly, the mirror reflectivity is mapped in order to find an optimum cavity design which maximizes the wall-plug efficiency (WPE). An increased WPE enables a higher output power, since the lower thermal dissipation limits the heating. A WPE around 5 % at a 4.5-mW output power was observed. Secondly, booster semiconductor optical amplifiers (SOAs) can be placed at the laser output, and the saturation power can be increased by tapering the active waveguide. Around 60 mW of output power was achieved for a 500-µm long SOA with a 2-µm to 4-µm linear taper. In conclusion, we have shown that lasers on the considered generic foundry platform can be optimized from a circuit level perspective. Due to the flexibility of the FM, this can potentially benefit a wide range of applications, such as optical communications, sensing, lidars, spectroscopy, and many others.