Feedback Dynamics of Multimode Lasers for Microwave Generation

Abstract

Photonic microwave generation has played a vital role in radio-over-fiber communication, due to its ability to transmit microwave signals over optical fibers with no electromagnetic interference and low propagation loss. Majority of the photonic approaches for the generation of tunable, high-purity radiofrequency signals employ the use of single mode lasers. This project deals with the investigation of multimode semiconductor lasers for generating widely-tunable microwave signals. The proposal covers the criteria required for microwave generation, and is a much cheaper solution. The dynamics of modulated feedback, driven by a microwave signal source giving side-mode locking to yield a frequency comb, has been thoroughly studied. The emphasis is on applying modulation at integer multiples of free spectral range (FSR/n) of the multimode laser. The characteristics of self-modulated feedback have been analyzed by the study of corresponding optical and power spectra. The inherent property of free spectral range of commercially available multimode lasers has been utilized to offer a simple, yet effective approach for microwave generation.