Due to its unique property of large time-bandwidth product (TBWP), the linear chirped microwave (LCMW) signal is highly desirable in many aspects, including the modern radar system and optical instruments, since larger TBWP indicates higher range resolution. The conventional methods to generate the LCMW always rely on the electrical devices, such as the electronic oscillator or the digital waveform generator, which have limitations in speed, bandwidth, and power consumption due to the electronic bottleneck. However, most reported solutions using the microwave photonics were based on discrete fiber devices, which are difficult to be integrated.

Based on these problems above, the Professor Jianji Dong’s team proposed and experimentally demonstrated a novel LCMW generator utilizing the slow light effect in the photonic crystal waveguide. The footprint of the chip is only 0.096 mm2, which is the smallest LCMW generator, to the best of our knowledge, as the Fig. 1 shows. The generated LCMW has good quality with the TBWP of 30, as the Fig. 2 shows. The proposed scheme which might be valuable towards the large scale integrated microwave photonics chip.

On September 1, 2017, this work is published on Optics Letter (Volume 42,Issue 17, Pages 3299-3302) with the title of Photonic linear chirped microwave signal generation based on the ultra-compact spectral shaper using the slow light effect. The work is supported by the National Natural Science Foundation of China (NSFC) (61475052, 61622502); Opened Fund of the State Key Laboratory on Advanced Optical Communication System and Network (2015GZKF03004); Program for New Century Excellent Talents in Ministry of Education of China (NCET-11-0168).