Tunable Narrow-Linewidth Photonic Microwave Oscillators Using Optically Injected Semiconductor Lasers at Period-One Dynamics
Yu-Han Hung1*, Sheng-Kwang Hwang1,2
1Department of Photonics, National Cheng Kung University, Tainan, Taiwan
2Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan
* presenting author:洪裕涵, email:yhh19880411@gmail.com
Period-one (P1) dynamics excited in an optically injected semiconductor laser have been widely investigated not only for academic interest in understanding nonlinear dynamics but also for practical interest for novel technological applications. Thanks to the self-sustained microwave oscillation of the laser intensity, P1 dynamics can be applied for photonic microwave generation. While the microwave frequency can be broadly tuned from a few to tens and even hundreds of gigahertz by simply adjusting the optical injection power and frequency, optical single-sideband modulation is so feasible as to mitigate microwave power fading over fiber distribution. However, owing to the inartistic laser noise, the linewidth of the photodetected microwaves is typically on the order of tens to hundreds of megahertz. To stabilize the photodetected microwaves, several stabilization schemes have been proposed, including direct modulation, optoelectronic feedback, and optical feedback. However, these proposed schemes suffer from either device bandwidth restriction or significant frequency jitter, limiting respectively the highest lockable microwave frequency, up to 25 GHz, or the lowest stabilized microwave linewidth, down to the order of kilohertz only. In this study, we propose to use modulation sideband injection locking scheme to stabilize the P1 dynamics. A 3-dB linewidth of 1 Hz is experimentally demonstrated for microwave generation up to 32 GHz using an electronic microwave reference at a small fraction, such as one-eights, of the generated microwave frequency. A higher-frequency microwave generation is feasible, such as 100 GHz or more, using devices of higher bandwidth.

Keywords: nonlinear dynamics, semiconductor lasers, microwave photonics, optical communications