Photonic-Assisted Programmable Ultra-Wideband Frequency-Modulated Continuous-Wave Generator

A frequency-modulated continuous-wave (FMCW) generator with an ultra-large time-bandwidth product (TBWP) is crucial in modern radar systems. Herein we propose and experimentally demonstrate a programmable FMCW generator with an ultra-large TBWP based on two three-electrode distributed Bragg reflector (DBR) laser diodes (LDs) and one photodetector (PD). Thanks to the rapid response of the refractive index to the injection current in the passive phase control section, which is caused by the free-carrier plasma effect, the three-electrode DBR LD takes advantage of programmable and ultra-fast wavelength tuning. In the proposed FMCW generator, a programmable current source injects one three-electrode DBR LD to generate a broadband frequency-chirped optical signal. A constant current source injects the other one to perform a stable optical carrier. By beating the frequency-chirped optical signal and the optical carrier at the PD, a programmable FMCW is generated. Experimental results show that an ultra-wideband FMCW generator with full reconfigurability in modulation type, bandwidth, center frequency, chirp rate, and temporal duration is realized. A chirp rate over 10 GHz/μs and a TBWP up to 2 × 10
⁷
are experimentally demonstrated. Thanks to the monolithic integration of the critical devices, including two three-electrode DBR LDs and one PD, the demonstration promises breakthroughs in small-size and high-performance FMCW generators, facilitating applications in autonomous vehicles and space exploration systems.