Singh Neetesh, Kärtner Franz X
Opt Express. 2022 Feb 14;30(4):5973-5980. doi: 10.1364/OE.447205.
Isolators are important devices in optics, especially for low noise systems, as even a small amount of back reflection can be detrimental to the quality of the signal generated by the source impacting downstream applications. Traditionally, magneto-optical materials have been used in isolators for bulk and fiber based optical systems. However, they tend to have high insertion loss, and are complicated to integrate on a photonics chip. Another class of isolators is based on optical nonlinearity that do not require external magnetic bias. However, the devices demonstrated so far suffer from either limited bandwidth, high insertion loss or fabrication complexity. In this work, we demonstrate a monolithic, fully complementary metal-oxide-semiconductor compatible, nonlinear Mach-Zehnder interferometer isolator based on third order optical nonlinearity, that overcomes such issues. In this proof of principle study, we show up to 15 dB isolation with 0.4 dB insertion loss and a device footprint of 0.4 mm which can easily be improved on further. The device is broadband and is independent of wavelength, material, and the platform. Not only can such a device be used for integrated optical systems but also for the fibre based optical systems.
隔离器是光学领域的重要器件，尤其对于低噪声系统而言，因为即使少量的背向反射也可能对光源产生的信号质量产生不利影响，进而影响下游应用。传统上，磁光材料已用于基于体材料和光纤的光学系统的隔离器中。然而，它们往往具有较高的插入损耗，并且在光子芯片上集成起来很复杂。另一类隔离器基于光学非线性，不需要外部磁偏置。然而，到目前为止所展示的器件存在带宽有限、插入损耗高或制造复杂性高等问题。在这项工作中，我们展示了一种基于三阶光学非线性的单片、完全互补金属氧化物半导体兼容的非线性马赫曾德尔干涉仪隔离器，该隔离器克服了这些问题。在这项原理验证研究中，我们展示了高达15dB的隔离度、0.4dB的插入损耗以及0.4mm的器件尺寸，并且可以很容易地进一步改进。该器件具有宽带特性，与波长、材料和平台无关。这种器件不仅可用于集成光学系统，也可用于基于光纤的光学系统。
