Photonic Microwave Generation Based On Vertical-cavity Surface-emitting Lasers Subject To Elliptically Polarized Optical Injection

The Radio-over-Fiber(RoF) is a new communication technology that effectively combines the large capacity of optical fiber communication with wireless communication, which can use the optical fiber link to transport the radio signal. The characteristics of technology are high confidentiality, electromagnetic interference resistance, low cost, easy installation. With the aid of fiber link, the radio signal can be assigned from central station to other base stations, and then the collected radio signal at base stations is transported to central station. As one of the key technologies for supporting the RoF, the generation of high quality photonic microwave is becoming hot spot in communication research. Currently, there are a variety of methods for generating photonic microwave, mainly including optical heterodyning, external modulation, direct modulation, combining dual-mode semiconductor laser and period-one(P1) oscillation in optically injected semiconductor laser. Recently, a method based on optically injected semiconductor lasers to generate photonic microwave has been proposed, due to the characteristics of single side band(SSB) and adjustable frequency, it is highly concerned by related researchers.In this paper, we propose a scheme on simultaneous generation of two channel photonic microwave based on the P1 oscillations of two orthogonally polarization modes in a vertical-cavity surface-emitting laser(VCSEL) subject to an elliptical polarization optical injection, and the related characteristics of obtained photonic microwave are numerically simulated and analyzed. The results show that under suitable operational parameters, a free-running VCSEL(named as master VCSEL, M-VCSEL) can output an elliptical polarization light in which both X and Y polarization components of the elliptical polarization light oscillate at same frequency. By using the elliptical polarization light from the M-VCSEL as an injection light into another VCSEL(named as slave VCSEL, S-VCSEL), both two polarization components of the S-VCSEL can be driven into period-one(P1) oscillation through selecting suitable injection strength under a fixed frequency detuning between the M-VCSEL and the S-VCSEL. Based on the P1 oscillation, two orthogonally photonic microwave signals can be obtained. With the increase of the injection strength from the M-VCSEL, the frequency of photonic microwave shows a gradually increasing trend while the power of photonic microwave behaves an increasing process accompanied by slight ripples. Combining the distribution mappings of the frequency, the power, and the amplitude difference between the first sideband and the second sideband of the photonic microwave in the parameter space of the injection strength and the frequency detuning, certain regions with optimally operational parameters can be determined for acquiring high quality photonic microwave. At the same time, the photonic microwave with single side band can reduce the influence of fiber dispersion and improve the transmission performance of RoF system.