Bent silicon slot waveguides with both low loss and low nonlinearity
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Bent silicon slot waveguides with both low loss and low nonlinearity Yameng Xu1 · Jiaxuan Li1 · Mei Kong1 · Chen Chen1 Received: 31 December 2019 / Accepted: 24 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract With the development of highly integrated linear optical systems, both low loss and low nonlinearity are demanded for silicon slot waveguides with a small bending radius. In this paper, we calculate the variations of loss and nonlinearity with the bending radius of aircladding and silica-cladding slot waveguides, and the mechanisms underlying the variations are revealed. We show that slot waveguides with symmetric silicon arms cannot possess low nonlinearity and low loss simultaneously due to the serious optical power leakage to the substrate. To solve this issue, asymmetric silicon arms are employed. By increasing the width of the inner arm, the high power confinement in the slot can be ensured, and this also makes the simultaneous low loss and low nonlinearity possible. We show that the silica-cladding slot waveguide under a 5 μm radius can obtain power confinement, loss and nonlinearity as respectively 40%, 1.17 × 10−4 dB/μm and 16.41/W/m, which are all comparable with those in the straight slot waveguide. Keywords Bent slot waveguides · Nonlinearity · Loss · Power confinement
1 Introduction Silicon-on-insulator (SOI) platform (Bogaerts et al. 2005; Aalto et al. 2019) has already gained a foothold as a foundation for the silicon photonic chip industry in terms of compatibility with the complementary metal–oxide–semiconductor (CMOS) technology, transparency at telecom wavelengths and high refractive index contrast, which allows a tight confinement of light within the waveguides. Numerous devices exploiting linear optical phenomena have been realized on the SOI platform, for instance, optical buffers (Xie et al. 2014; Moralis-Pegios et al. 2018), optical interconnects (Kumar and Priye 2017, 2018), integrated optical sensors (Zhao et al. 2018; Singh et al. 2019) and so on. However, the relatively large nonlinear coefficient of silicon can degrade the performances of the linear SOI devices. For example, for the silicon waveguide with a nonlinear coefficient of 307/W/m (Vallaitis et al. 2009), the nonlinear length (Agrawal 2013) is only 3.3 cm for an * Yameng Xu [email protected] 1
Department of Optoelectronic Information Science and Technology, School of Science, Changchun University of Science and Technology, 7089 Weixing Road, Changchun 130022, China
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optical peak power of 100 mW. If the nonlinear coefficient can be reduced by two orders, the nonlinear length can also be extended by two orders. The SOI slot waveguide (Almeida et al. 2004; Ségolène and Matthieu 2019), localizing a large part of guided-mode field in air or a low nonlinear dielectric, has attracted attention as a promising candidate to depress the nonlinearity and be utilized in linear SOI devices. Till now, the investigations
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