Enhancing Nonlinear Kerr effect in Silicon Nitride Waveguides

通过新兴的CMOS兼容硅光子学平台，可以提供并且将需要该平台中的更复杂的功能。克尔非线性是一种效应，可用于各种光学信号处理应用，如光学采样，参量放大，波长转换等，到目前为止，这种效应已被用于光纤，但集成克尔非线性也可以在不久的将来用于信号处理的目的。硅波导最初已被研究用于此目的，但由于硅中的双光子吸收（TPA）很强，累积的非线性相移被限制在几个弧度。虽然氮化硅具有比硅低的克尔非线性系数，但由于其具有低得多的TPA系数，因此其具有提供更多累积非线性相移的潜力。在本计画中，计画最大化矽氮化物波导中因克尔效应所造成的累积非线性相移。慢光结构将被研究以增强结构内部的光场，并提供将增强克尔非线性的减速因子。在各种慢光结构中，我们将考虑波纹波导（一维光子晶体）、二维线缺陷光子晶体和耦合环形谐振腔。此外，硅和氮化硅的混合组合（因为两者都可以很容易地用于CMOS工厂中的绝缘体上硅晶片）也将被研究，以进一步提高克尔非线性系数。 基于大量文献综述的分析模型将用于准备慢光结构的设计，并将进行大量数值模拟来分析设计的结构并发现其对制造公差的鲁棒性。设计将准备和发送流出来，最后制造结构的特点。 我们试图找到最终的限制结构铺平道路，利用克尔非线性氮化硅波导的光信号处理。

By emerging CMOS compatible silicon photonics platform, more complex functionalities in this platform can be offered and will be demanded. Kerr nonlinearity is an effect which can be used for various optical signal processing applications like optical sampling, parametric amplification, wavelength conversion, etc. So far, this effect has been used in optical fibers, but integrated Kerr nonlinearity can also be exploited in the near future for signal processing purposes. Silicon waveguides have been initially investigated for this purpose but since two photon absorption (TPA) is strong in silicon, accumulated nonlinear phase shift is limited to a few radians. Although, silicon nitride has lower Kerr nonlinear coefficient than silicon, since it has much lower TPA coefficient, it has the potential to provide more accumulated nonlinear phase shift. In this project, it is planned to maximize the accumulated nonlinear phase shift caused by Kerr effect in silicon nitride waveguides. Slow light structures will be investigated to enhance the optical field inside the structure and provide a slowdown factor which would intensify the Kerr nonlinearity. Among the various slow light structures, we will consider corrugated waveguides (one dimensional photonic crystal), two dimensional photonic crystals with line defect and coupled ring resonators. Also a mixed combination of silicon and silicon nitride (since both can be used easily on silicon on insulator wafers in a CMOS fab) will also be investigated to further enhance Kerr nonlinearity coefficient. Analytical models based on an intensive literature review will be used to prepare the design of the slow light structures and intensive numerical simulations will be performed to analyze the designed structures and find their robustness to fabrication tolerance. The designs will be prepared and sent for tape out and finally the fabricated structures will be characterized. We try to find the ultimate limitations of the structures to pave the way for optical signal processing using Kerr nonlinearity in silicon nitride waveguides.