Experimental Demonstration of Amplified Feedback DFB Laser With Modulation Bandwidth Enhancement Based on the Reconstruction Equivalent Chirp Technique

摘要

The amplified feedback structure of this laser, which can avoid the butt-joint re-growth process, can enhance the performance of modulation response of a directly modulated semiconductor laser (DML) by taking advantage of photon-photon resonance effects. The sophisticated gratings in laser cavity can be formed by conventional holographic exposure combining with a conventional photolithography. Hence, this work provides a novel low-cost solution to realizing high-performance DMLs.A novel amplified feedback DFB laser with extended modulation bandwidth is experimentally demonstrated in this paper. All the three sections of laser cavity, including DFB section, phase section, and amplified feedback section, have the same active layer, which can avoid the butt-joint regrowth process. The gratings in both DFB section and amplified feedback section are fabricated by the reconstruction equivalent chirp technique, which can significantly decrease the difficulties in realizing precise grating structure. An enhanced −3 dB bandwidth of 19 GHz is achieved by means of a normal low-frequency wafer. Modulation linearity and relative intensity noise characteristics are experimentally investigated. 20 MSymbol/s 32-QAM signal with 19 GHz carrier is transmitted via 25-km radio-over-fiber link using the as-fabricated directly modulated DFB laser, and the average error vector magnitude of the whole link is 3.91%.