Opt Express. 2023 Feb 13;31(4):6577-6589. doi: 10.1364/OE.481946.
The traveling-wave like Fabry-Perot (F-P) resonators based on transverse-mode-conversion have been extensively studied as on-chip filters. However, the incomplete transverse mode conversion will lead to the coupling between two degenerated resonant modes, which brings additional loss and may further induce the resonance splitting. In this paper, we take the transverse-mode-conversion based resonator with anti-symmetric nanobeam Bragg reflector as an example and study the resonant mode coupling in both the direct-coupled and side-coupled resonators. The coupled mode equations are used to model the incomplete transverse mode conversion of Bragg reflector. The resonant mode coupling can be effectively suppressed by carefully designing the phase shifter length and adding the tapered holes. The insertion loss of less than -1 dB can be achieved in the simulation using the two methods. This work is believed to benefit the design of mode-conversion based resonators with low insertion loss and non-splitting line shape.
基于横模转换的行波法布里-珀罗（F-P）谐振器已被广泛研究作为片上滤波器。然而，不完全的横模转换会导致两个简并谐振模式之间的耦合，这会带来额外的损耗，并可能进一步导致谐振分裂。在本文中，我们以具有非对称纳米梁布拉格反射器的横模转换谐振器为例，研究了直接耦合和侧面耦合谐振器中的谐振模式耦合。采用耦合模方程来模拟布拉格反射器不完全的横模转换。通过仔细设计相移器长度和添加锥形孔，可以有效地抑制谐振模式耦合。使用这两种方法在模拟中可以实现小于-1dB 的插入损耗。这项工作有望有益于设计具有低插入损耗和非分裂线性形状的基于模式转换的谐振器。
