Ferise Clément, Del Hougne Philipp, Félix Simon, Pagneux Vincent, Davy Matthieu
Univ Rennes, CNRS, IETR-UMR 6164, F-35000 Rennes, France.
Laboratoire d'Acoustique de l'Université du Mans (LAUM), UMR 6613, Institut d'Acoustique - Graduate School (IA-GS), CNRS, Le Mans Université, France.
Phys Rev Lett. 2022 May 20;128(20):203904. doi: 10.1103/PhysRevLett.128.203904.
We investigate experimentally and analytically the coalescence of reflectionless (RL) states in symmetric complex wave-scattering systems. We observe RL exceptional points (EPs), first with a conventional Fabry-Perot system for which the scattering strength within the system is tuned symmetrically and then with single- and multichannel symmetric disordered systems. We confirm that an EP of the parity-time (PT)-symmetric RL operator is obtained for two isolated quasinormal modes when the spacing between central frequencies is equal to the decay rate into incoming and outgoing channels. Finally, we leverage the transfer functions associated with RL and RL-EP states to implement first- and second-order analog differentiation.
我们通过实验和分析研究了对称复波散射系统中无反射（RL）态的合并。我们观察到了RL例外点（EP），首先是使用传统的法布里-珀罗系统，其中系统内的散射强度被对称地调谐，然后是单通道和多通道对称无序系统。我们证实，当中心频率之间的间距等于进入和离开通道的衰减率时，对于两个孤立的准正常模式，可获得宇称-时间（PT）对称RL算子的一个EP。最后，我们利用与RL和RL-EP态相关的传递函数来实现一阶和二阶模拟微分。
