Konotop Vladimir V, Sanders Barry C, Zezyulin Dmitry A
Opt Lett. 2019 Apr 15;44(8):2024-2027. doi: 10.1364/OL.44.002024.
Two microring resonators, one with gain and one with loss, coupled to each other and to a bus waveguide, create an effective non-Hermitian potential for light propagating in the waveguide. Due to geometry, the coupling for each microring resonator yields two counter-propagating modes with equal frequencies. We show that such a system enables implementation of many types of scattering peculiarities. The spectral singularities, which are either the second or fourth order, separate parameter regions where the spectrum is either purely real or composed of complex eigenvalues; hence, they represent the points of the phase transition. By modifying the gain-loss relation for the resonators, such an optical scatterer can act as a laser, as a coherent perfect absorber, be unidirectionally reflectionless or transparent, and support bound states either growing or decaying in time. These characteristics are observed for a discrete series of the incident-radiation wavelengths.
两个微环谐振器，一个具有增益，一个具有损耗，它们相互耦合并与一条总线波导耦合，为在波导中传播的光创造了一个有效的非厄米势。由于几何结构，每个微环谐振器的耦合产生两个频率相等的反向传播模式。我们表明，这样的系统能够实现多种类型的散射特性。光谱奇点，其为二阶或四阶，分隔了光谱为纯实数或由复本征值组成的参数区域；因此，它们代表了相变点。通过修改谐振器的增益-损耗关系，这样的光学散射体可以充当激光器、相干完美吸收体、单向无反射或透明，并支持随时间增长或衰减的束缚态。这些特性在一系列离散的入射辐射波长中被观察到。
