Opt Express. 2023 Apr 24;31(9):14986-14996. doi: 10.1364/OE.488467.
Gain and loss balanced parity-time (PT) inversion symmetry has been achieved across multiple platforms including acoustics, electronics, and photonics. Tunable subwavelength asymmetric transmission based on PT symmetry breaking has attracted great interest. However, due to the diffraction limit, the geometric size of an optical PT symmetric system is much larger than the resonant wavelength, which limits the device miniaturization. Here, we theoretically studied a subwavelength optical PT symmetry breaking nanocircuit based on the similarity between a plasmonic system and an RLC circuit. Firstly, the asymmetric coupling of an input signal is observed by varying the coupling strength and gain-loss ratio between the nanocircuits. Furthermore, a subwavelength modulator is proposed by modulating the gain of the amplified nanocircuit. Notably, the modulation effect near the exceptional point is remarkable. Finally, we introduce a four-level atomic model modified by the Pauli exclusion principle to simulate the nonlinear dynamics of a PT symmetry broken laser. The asymmetric emission of a coherent laser is realized by full-wave simulation with a contrast of about 50. This subwavelength optical nanocircuit with broken PT symmetry is of great significance for realizing directional guided light, modulator and asymmetric-emission laser at subwavelength scales.
在包括声学、电子学和光子学在内的多个平台上已经实现了增益和损耗平衡的宇称时间（PT）反转对称。基于 PT 对称破缺的可调亚波长非对称传输引起了极大的兴趣。然而，由于衍射极限，光学 PT 对称系统的几何尺寸远大于共振波长，这限制了器件的小型化。在这里，我们基于等离子体系统和 RLC 电路之间的相似性，从理论上研究了一种亚波长光 PT 对称破缺纳米电路。首先，通过改变纳米电路之间的耦合强度和增益-损耗比，观察到输入信号的不对称耦合。此外，通过调制放大纳米电路的增益，提出了一种亚波长调制器。值得注意的是，在异常点附近的调制效果非常显著。最后，我们引入了一个由泡利不相容原理修正的四能级原子模型，以模拟 PT 对称破缺激光的非线性动力学。通过全波模拟实现了具有约 50 的对比度的相干激光的非对称发射。这种具有破缺 PT 对称的亚波长光学纳米电路对于实现亚波长尺度的定向导光、调制器和非对称发射激光具有重要意义。
