||Low-cost and high-speed optical transmitter for achieving high capacity of data transmission is necessary. Photonic integration of laser and modulator thus becomes one of the major technologies. Electroabsorption modulator integrated laser (EML) is one of the solutions fulfilling high speed, high modulation efficiency, compact size, and low chirp characteristics. However, there are still some technologies for enhancing transmitter performance, for example, bandgap offset between laser and modulator, and trade-off issue between speed and efficiency. In this work, a vertical couple and traveling wave electrode structure is proposed and demonstrated to integrate distributive feedback laser, semiconductor optical amplifier (SOA), and electroabsorption modulator (EAM).|
To avoid MQW oxidation in regrowth processing, two sets of stacked InGaAsP/InGaAsP multiple quantum well (MQW), one for laser and SOA and the other for EAM, is utilized in this work, where the modulator is defined by wet etching top laser MQW and SOA are is defined by removing top grating layer. Notably, all the processing is based on wet etching and binary re-growth technology, enabling low cost fabrication.
In order to reduce lump RC element limitation, a traveling wave electrode, semi-insulate substrate, and reverse ridge waveguide are applied for fabricating EML. At room temperature condition, the output power of DFB laser exceeds 2mW. By over etching grating layer, the side mode suppress ratio (SMSR) greater than 40dB is observed. Over 25dB extinction ratio and 7dB modulation efficiency (dT/dV), and over 12dB gain SOA gain are obtained in EAM and SOA. With traveling wave electrode, 3dB bandwidth of 35GHz EML with 40Gb/s data transmission are attained, enabling the application of low-cost and broad band Ethernet network.