Cao Ruidong, Wang Guangying, Li Minghai, Zhang Jiejun, Yao Jianping
Opt Express. 2022 Feb 14;30(4):4737-4747. doi: 10.1364/OE.449472.
A photonic approach to generate a linearly chirped microwave waveform (LCMW) with an ultra-long temporal duration is proposed and experimentally demonstrated. The microwave waveform generation is achieved based on spectral-shaping and wavelength-to-time (SS-WTT) mapping by using a Mach-Zehnder interferometer (MZI) and a frequency-shifting dispersive loop (FSDL), respectively. To make the generated microwave waveform have an ultra-long temporal duration, the FSDL is operating to allow a spectrally shaped optical pulse to recirculate in a dispersive loop multiple times with a low propagating loss, to generate a microwave waveform with a temporal duration that is more than one order of magnitude longer than that of a microwave waveform generated using a dispersive element without recirculation. To generate a LCMW, the spectral shaper is configured to have a free spectral range (FSR) that is linearly increasing or decreasing with optical wavelength. The proposed approach is experimentally demonstrated. Two LCMWs, by allowing an optical pulse recirculating in the FSDL for three and seven round trips, tripled and septupled temporal durations of 64 and 182 ns are generated. The generation of two LCMWs with ultra-long temporal durations of 370 ns and 450 ns are also demonstrated.
提出并通过实验证明了一种用于生成具有超长持续时间的线性啁啾微波波形（LCMW）的光子学方法。微波波形的生成分别基于使用马赫-曾德尔干涉仪（MZI）的频谱整形和使用移频色散环（FSDL）的波长到时间（SS-WTT）映射来实现。为了使生成的微波波形具有超长的持续时间，FSDL运行以允许频谱整形的光脉冲在色散环中以低传播损耗多次循环，从而生成一个持续时间比使用无循环的色散元件生成的微波波形长一个数量级以上的微波波形。为了生成LCMW，频谱整形器被配置为具有随光波长线性增加或减少的自由光谱范围（FSR）。所提出的方法通过实验得到了证明。通过允许光脉冲在FSDL中循环三圈和七圈，生成了两个LCMW，其持续时间分别为64纳秒和182纳秒，分别增加了两倍和七倍。还展示了生成两个持续时间分别为370纳秒和450纳秒的超长持续时间的LCMW。
