Chen Haojia, Gao Qiong, Qian Baoliang, Zhao Lishan
College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China.
Luoyang Electronic Experiment Testing Centre, Luoyang 471003, China.
Materials (Basel). 2019 Oct 31;12(21):3588. doi: 10.3390/ma12213588.
Fundamentally different responses of a LiTaO 3 thin film detector are observed when it is subjected to short microwave pulses as the pulse intensity is altered over a wide range. We start from weak microwave pulses which lead to only trivial pyroelectric peak response. However, when the microwave pulses become intense, the normally expected pyroelectric signal seems to be suppressed and the sign of the voltage signal can even be completely changed. Analysis indicates that while the traditional pyroelectric model, which is a linear model and works fine for our data in the small regime, it does not work anymore in the large signal regime. Since the small-signal model is the key foundation of electromagnetic-wave sensors based on pyroelectric effects, such as pyroelectric infrared detecters, the observation in this work suggests that one should be cautious when using these devices in intense fields. In addition, the evolution of detector signal with respect to excitation strength suggests that the main polarisation process is changed in the large signal regime. This is of fundamental importance to the understanding on how crystalline solids interact with intense microwaves. Possible causes of the nonlinear behaviour is discussed.
当LiTaO₃薄膜探测器受到短微波脉冲照射，且脉冲强度在很宽的范围内变化时，会观察到其响应有根本不同。我们从弱微波脉冲开始，此时只会产生微不足道的热释电峰值响应。然而，当微波脉冲变强时，正常预期的热释电信号似乎受到抑制，甚至电压信号的符号都可能完全改变。分析表明，虽然传统的热释电模型是线性模型，在小范围内对我们的数据适用，但在大信号范围内不再适用。由于小信号模型是基于热释电效应的电磁波传感器（如热释电红外探测器）的关键基础，这项工作中的观察结果表明，在强场中使用这些设备时应谨慎。此外，探测器信号随激发强度的变化表明，在大信号范围内主要极化过程发生了变化。这对于理解晶体固体如何与强微波相互作用至关重要。讨论了非线性行为的可能原因。
