Investigation On The Narrow-linewidth Photonic Microwave Generation Using 1550 Nm Vertical-cavity Surface-emitting Laser Under External Optics Disturbances

The Radio-over-Fiber(RoF) is a communication technology which brings the agility of wireless communication and huge capacity of optical fiber communication together.It has an attractive application prospect in next-generation broadband communications system. The photonic microwave technology, one of the key technology of Ro F, become a research hotspot in recent years. So far, different photonic microwave generation schemes have been proposed and investigated, such as the optical heterodyne method based on the beat of two independent lasers, the external modulation method based on electro-optical modulator, the dual-mode beat method based on the monolithic dual-mode semiconductor lasers and the optoelectronic microwave oscillator(OEO)method based on optoelectronic feedback loops. These schemes have their own advantages and deficiencies. In recent years, the exploration of the periodic oscillation of semiconductor laser as the photonic microwave signal source have received scholars attention. However, photonic microwave signal generated from semiconductor laser periodic oscillation is mainly based on the edge-emitting semiconductor laser(EEL).Photonic microwave source using the rapidly improving vertical cavity surface emitting laser(VCSEL) is still relatively lack. Compared with EEL, VCSEL has a series of advantages, such as: low threshold current, easy to integrate, easy and fiber coupling,high modulation bandwidth, low manufacturing cost. It is very possible to replace the EEL and to become the core components of next generation optical communication and signal processing in the future.This paper proposes an all optical scheme for generating high-quality microwave based on a 1550 nm vertical-cavity surface-emitting laser(1550 nm-VCSEL). For such a scheme, high frequency microwave is obtained based on a 1550 nm-VCSEL subject to optical injection from the external light, whose polarization is same with that of the dominant mode of the free-running 1550 nm-VCSEL(named as parallel polarizationoptical injection) and wavelength locates near the wavelength of the suppressed mode of free-running 1550 nm-VCSEL, and the linewidth of the microwave is narrowed with the aid of double optical feedback. Firstly, the feasibility of microwave generation based on parallel polarization optically injected 1550 nm-VCSEL is analyzed theoretically by the aid of the spin-flip model(SFM) of VCSEL. Next, the corresponding experiment system is constructed, and the performances of microwave generation is preliminary investigated experimentally. The experimental results show that 30 GHz microwave signals could be obtained based on a parallel polarization optically injected 1550nm-VCSEL under suitable injection conditions, but the linewidth of microwave signals are relatively wide(on the level of hundred MHz). After introducing double optical feedback, the linewidth of microwave signals can be reduced more than two orders of magnitude and less than 1 MHz, and meanwhile the signal-noise ratio is larger than 40 dB. Above proposed scheme is all optical, without using the expensive high-frequency electronic devices. Therefore, it us useful for the development of low cost, high performance and narrow linewidth photonic microwave technology.