Dual-loop fourier domain mode-locked optoelectronic oscillator based on three-section mutual-injection integrated semiconductor laser

A directly-modulated Fourier domain mode-locked optoelectronic oscillator (FDML_OEO) based on three-section mutual-injection integrated semiconductor laser (TS_MIISL) with dual-loop feedback structure is proposed and experimentally demonstrated in this paper. By driving the TS_MIISL to work under the period-one (P1) state and modulating the TS_MIISL with low-repetition-rate sawtooth drive signal, a linear frequency-modulated (LFM) signal can be generated. Through adjusting the delay time of the feedback loops to match with the time duration of drive signal, the LFM signal can be significantly optimized in terms of spectral purity. In such a proposed FDML_OEO, no external modulator, polarization controller (PC) and filter are utilized, leading to an outstanding advantage in terms of stable performance and compact structure. The high-purity LFM signal with center frequency and bandwidth of 14 GHz and 8 GHz is obtained. The maximum time-bandwidth product (TBWP) of generated LFM signal could reach up to 48800. Due to the introduction of dual feedback loop, the frequency comb contrast and linewidth could reach up to 45 dB and 5 kHz, respectively. The center frequency and bandwidth of the generated signals are both tunable. A demonstration is made to prove that the pre-compensation processing could improve the linearity of LFM signals.