Liu Yanzhong, Hao Tengfei, Li Wei, Capmany Jose, Zhu Ninghua, Li Ming
1State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083 China.
2School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing, 100049 China.
Light Sci Appl. 2018 Jul 18;7:38. doi: 10.1038/s41377-018-0035-8. eCollection 2018.
Symmetry plays a crucial role in explorations of the laws of nature. Parity-time (PT) symmetry phenomena can lead to entirely real spectra in non-Hermitian systems, which attracts considerable attention in the fields of optics and electronics because these phenomena provide a new tool for the manipulation of oscillation modes and non-reciprocal signal transmission. A potential new field of application is microwave photonics, an interdisciplinary field in which the interaction between microwaves and optical signals is exploited. In this article, we report the experimental use of PT symmetry in an optoelectronic oscillator (OEO), a key microwave photonics system that can generate single-frequency sinusoidal signals with high spectral purity. PT symmetry is theoretically analyzed and experimentally observed in an OEO with two mutually coupled active oscillation cavities via a precise manipulation of the interplay between gain and loss in the two oscillation cavities. Stable single-frequency microwave oscillation is achieved without using any optical/electrical filters for oscillation mode selection, which is an indispensable requirement in traditional OEOs. This observation opens new avenues for signal generation and processing based on the PT symmetry principle in microwave photonics.
对称性在自然规律探索中起着至关重要的作用。宇称 - 时间（PT）对称现象可在非厄米系统中产生完全实的谱，这在光学和电子学领域引起了相当大的关注，因为这些现象为操纵振荡模式和非互易信号传输提供了一种新工具。一个潜在的新应用领域是微波光子学，这是一个利用微波与光信号相互作用的跨学科领域。在本文中，我们报告了PT对称在光电振荡器（OEO）中的实验应用，OEO是一种关键的微波光子学系统，能够产生具有高光谱纯度的单频正弦信号。通过精确操纵两个振荡腔中增益与损耗之间的相互作用，在具有两个相互耦合的有源振荡腔的OEO中对PT对称进行了理论分析和实验观测。无需使用任何用于振荡模式选择的光学/电气滤波器即可实现稳定的单频微波振荡，而这是传统OEO中不可或缺的要求。这一观测结果为基于微波光子学中PT对称原理的信号产生和处理开辟了新途径。
