Fig. 1. Schematic diagram of RF signal generation circuit based on mutual locking among two DFB lasers and one SRL.

Fig. 2. Spectra of (a) dual DFB injection-locked SRL modes in the CCW and CW directions, and (b) generated RF signal by beating the two lasing modes in the CCW direction. Pdfb1,2=0.23  dBm, Psrl−fr=−20.3  dBm, and Δω=0.

Fig. 3. FN curves of DFB lasers, SRL, and the generated RF signals.

Fig. 4. Linewidth of the generated RF signal as a function of tuning frequency.

Fig. 5. Influence of backscattering coefficient and feedback phase change on the linewidth of the generated RF signal. (a) General evolution, with linewidth expressed in log, (b) results of two special k values. Pdfb1,2=0.23  dBm, Psrl=−20.3  dBm, and Δω=0.

Fig. 6. Linewidth of the generated RF signal (in log) as a function of (a) power ratio (Pdfb/Psrl), where Pdfb=Pdfb1=Pdfb2 and Δω=0, and (b) power ratio (Pdfb2/Pdfb1), where Pdfb1=0.23  dBm and Δω=0.

Fig. 7. Linewidth of the generated RF signal (in log) as a function of the injection frequency detuning of the two DFB lasers.