Widely Tunable Two-Section Directly Modulated DBR Lasers for TWDM-PON System**Supported by the National Key Project under Grant No 2016YFB0402301, the National High Technology Research and Development Program of China under Grant No 2013AA014502, and the National Natural Science Foundation of China under Grant Nos 61635010, 61320106013, 61474112, 61321063 and 61274071.

Abstract

Wavelength tunable and directly modulated distributed Bragg reflector (DBR) lasers with butt-joint technology are designed, fabricated and characterized. The DBR laser consists of a gain section and a DBR section. To increase the electrical isolation between the gain section and the DBR section, parts of a p-doped material in the isolation region are etched off selectively. Over 2 kΩ isolation resistance is realized ultimately without the need of ion implantation, which simplifies the fabrication process. The laser exhibits high speed modulation with a large tunable range. The 3 dB direct modulation bandwidth of the device is over 8 GHz in a 12 nm tunable range. This widely tunable DBR laser with the simple structure is promising as a colorless light source for the next-generation time and wavelength division multiplexed passive optical network (TWDM-PON) systems.