Gain-Switched Optical Frequency Comb Source Using a Hybrid Integrated Self-Injection Locking DFB Laser

A hybrid integrated gain-switched (GS) optical frequency comb (OFC) source with eight pure continuous comb lines within 3-dB of the spectral envelope peak and a narrow linewidth of 615 kHz is proposed and demonstrated by coupling a silicon nitride microring reflector (MRR) to a commercially available distributed feedback (DFB) laser. Due to the self-injection locking effect induced by the MRR, the carrier-to-noise ratio (CNR) and phase correlation between comb lines are greatly enhanced. In addition, benefiting from the unique merit of gain switching, the resultant comb can also achieve a large frequency spacing adjustment range from 5.55 GHz to 8.7 GHz. This work explores a cost-efficient and robust OFC source for numerous applications, such as radio over fiber (RoF) and coherent optical communication.

Automated summary

This study presents a hybrid integrated gain-switched optical frequency comb source with eight pure continuous comb lines, a narrow linewidth, and a large frequency spacing adjustment range. By coupling a silicon nitride microring reflector to a commercially available distributed feedback laser, the self-injection locking effect greatly enhances the carrier-to-noise ratio and phase correlation between comb lines. This cost-efficient and robust comb source has potential applications in areas such as radio over fiber and coherent optical communication.