Microcomb-based reconfigurable LFM waveform generation

Optical frequency combs are commonly utilized for generating reconfigurable linearly-frequency-modulated (LFM) signals with a large operating frequency range in radar systems. However, traditional systems employing cascade delectro-optic modulators and relying on external electronic signal sources often suffer from high power consumption and bulky size. In contrast, chip-scale microcombs offer inherent advantages in terms of power efficiency and compactness. In this study, we propose and experimentally demonstrate a microcomb-based system for generating reconfigurable LFM signals. By self-injection locking a commercial distributed feedback laser chip through the backscattering of a micro resonator chip, a coherent microcomb state is achieved. Additionally, we utilize the wideband injection locking technique to enhance the signal-to-noise ratio, resulting in a significant power gain for the modulated sideband. The center frequency of the generated signals can be flexibly reconfigured by adjusting the selected comb line numbers and the frequency of the modulation signals. This enables the achievement of LFM signals with a large tunable range spanning from X- to W-bands. Furthermore, we analyze the characteristics of the produced LFM signal at Ka-band. Our measurements indicate a linearity of approximately 0.01% and a pulse compression ratio of approximately 2.1×10⁵. These results validate the effectiveness and potential of the proposed approach.