Wideband signal generation for radar application based on optically injected semiconductor laser

When a light is properly injected to a semiconductor laser (SL), periodic one (P1) dynamics can be excited and a microwave signal with a specific frequency can be generated after optical-to-electrical conversion. By varying the injection strength, the detuning frequency, or both, a continuously tunable microwave signal over a frequency range up to 100 GHz can be generated. Based on this principle, we implemented wideband linear frequency modulation (LFM) signal generation, which is highly required in high-resolution radars. While, this method suffers from a poor spectrum purity of the generated LFM signal, because the generated microwave using optically injected SL has a relatively large 3-dB linewidth on the order of megahertz. To overcome this problem, we applied a feedback to the optically injected SL with the round-trip time delay matched to the period of sweeping frequency, through which the spectrum purity of the obtained wideband LFM signals is greatly improve. Applying the generated broadband LFM signals, high-resolution radar target detection is demonstrated, which shows the good potential of the proposed wideband LFM signal generator in practical applications.