Abstract
Fundamentally different responses of a LiTaO 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.
Highlights
How dielectric materials respond to electromagnetic waves has long been a key topic in the physic research field
We show that when intense microwave pulses are really shed on a thin film sample of LiTaO3, which is a widely used dielectric and pyroelectric material, it gives dielectric response that is new and theoretically challenging
The material chosen in this work, LiTaO3, is a pyroelectric and a ferroelectric material, which has a wide range of applications in, for example, fire alarms, laser-energy meters, infrared (IF) thermal imaging, radiometers and energy harvesting [8,9,10,11,12], the common principle underlying all of which is the pyroelectric effect, an effect that was explained many decades ago [8,13,14]
Summary
How dielectric materials respond to electromagnetic waves has long been a key topic in the physic research field. A relatively complete theoretical framework was established on how they respond to weak and intense lasers, weak microwaves and static or slowly varying electric fields [1]; much less is known about how they respond to intense microwaves This is partially because, traditionally, knowing these materials’ small signal response is adequate for most practical applications, such as microwave communications [2,3,4,5], and facilities needed for this type of experiments (e.g., microwave sources of high-power output and a microwave chamber) are complicated and expensive.
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