Sputter-deposited magneto-optical garnet for all-mode (transverse electric/transverse magnetic) Faraday rotators
Sputter-deposited magneto-optical garnet for all-mode (transverse electric/transverse magnetic) Faraday rotators
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DOI：
10.1557/mrs.2018.121
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发表时间：
2018-06
期刊：
影响因子：
5
通讯作者：
B. Stadler;D. Hutchings
中科院分区：
文献类型：
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作者：
B. Stadler;D. Hutchings
光隔离器中的法拉第旋转器通常由铁石榴石组成，是电二极管的光子类似物，因为它们不允许光的相互传输。隔离器对于阻止背反射光到达源激光器特别重要，因为这种反馈会产生不必要的噪声和不稳定性。在通常实现的光子集成电路（PIC）中，隔离是唯一无法通过直接集成实现的关键功能。虽然已经探索了几种技术将高回转石榴石集成到绝缘体上硅PIC中，但本文重点介绍溅射沉积，这是最具可升级性的工艺。在非石榴石基片上用溅射沉积法制备高旋向性掺铈钇铁石榴石，并使用石榴石籽晶层。由于这些籽晶层会损害器件性能，因此最近也开发了无籽晶层的铽铁石榴石（TIG）。仔细掺杂TIG可以产生具有相反手性的法拉第旋转，这使得新的器件设计成为可能。大多数光隔离器设计涉及二维横磁模结构，如干涉仪或环形谐振器，采用非互易相移。具有准相位匹配的一维法拉第旋转波导已被证明能够直接集成所有模式的隔离器，包括目前可用于完全集成PIC的激光器的横向电模式。
Faraday rotators in optical isolators, typically composed of iron garnets, are photonic analogues of electrical diodes in that they do not allow reciprocal transmission of light. Isolators are especially important for blocking back-reflected light from reaching source lasers, as such feedback gives rise to unwanted noise and instabilities. In commonly implemented photonic integrated circuits (PICs), isolation is the only critical function that cannot yet be achieved by direct integration. While several techniques have been explored for integrating high-gyrotropy garnets into silicon-on-insulator PICs, this article focuses on sputter deposition, which is the most up-scalable process. High-gyrotropy Ce-doped yttrium iron garnet on nongarnet substrates can be made by sputter deposition with the use of garnet seed layers. Because these seed layers can compromise device performance, seed layer-free terbium iron garnet (TIG) has also recently been developed. Careful doping of TIG can produce Faraday rotations with opposite chiralities, which enable new device designs. Most optical isolator designs involve two-dimensional transverse magnetic-mode structures, such as interferometers or ring resonators, which employ nonreciprocal phase shift. One-dimensional Faraday rotation waveguides with quasi-phase matching have been shown to enable direct integration of isolators for all modes, including the transverse electric mode of lasers currently available for fully integrated PICs.