Reconfigurable Identical and Complementary Chirp Dual-LFM Signal Generation Subjected to Dual-Beam Injection in a DFB Laser

A photonic approach for identical and complementary chirp dual-linear frequency modulation (LFM) signal generation using an optical injection in a distributed feedback (DFB) laser is proposed and experimentally demonstrated. The proposed scheme is based on the redshift of the emission frequency in the DFB laser, and the nonlinear dynamics in the periodic oscillation of the DFB laser subjected to an optical injection. In the proposed scheme, two optical beams from master lasers, one with varying optical power and another with constant optical power, are injected to the slave laser, a DFB laser. The redshift of the mode in slave laser is due to the injection of the beam with varying optical power, which changes the frequency detuning of the injected beams and the mode of slave laser. Hence, a dual-LFM signal with a large time-bandwidth product (TBWP) is observed. Whether two beams are injected to the slave laser with positive frequency detunings or opposite frequency detunings, dual-LFM signal with the combinations of linearly increasing or/and decreasing frequency is obtained. With the proposed scheme, identical and complementary chirp dual-LFM signals with the same period of 1.3 μs have been obtained. The measured bandwidths for both LFM signals are 7 GHz (LFM1: 16.0-23.0 GHZ; LFM2: 25.0-32.0 GHz) with a TBWP of 9100. The generated dual-LFM signal has flexibility in tuning the center frequency and reconfiguring different IEEE radar bands.