基于FP腔实现光纤与边缘耦合器高效对准

Efficient Alignment of Optical Fibers and Edge Couplers based on FP Cavity

【目的】通过集成在片上的硅基边缘光耦合器(以下简称边缘耦合器),硅光子芯片可以与光纤实现低损耗耦合。在商用硅光子芯片的封装流程中,大规模的光纤与硅光子芯片对准需求对光纤与边缘耦合器的对准效率提出了更高的要求。文章的研究目的是基于光纤端面与边缘耦合器端面之间形成的法布里-珀罗(FP)腔对光纤与边缘耦合器的对准流程进行优化。在光纤轴向(文章中表示为x轴方向)这一自由度上对光纤与边缘耦合器之间的距离进行测量后,将光纤沿该方向进行单次调节即可完成与边缘耦合器的高精度对准。【方法】文章研究了光纤端面与边缘耦合器端面之间形成的FP腔结构,建立了FP腔的反射/透射光谱与端面间距之间的物理模型。搭建光纤对准平台完成了基于FP腔测量端面之间距离的实验,然后基于FP腔测距结果,将光纤沿光纤轴向进行单次位置调整来实现与边缘耦合器的对准。【结果】实验中得到的FP腔长值与仿真得到的理想FP腔模型腔长值的偏差小于1μm,测得的光纤位移距离在实际位移的误差范围(±1μm)内。基于测距结果调整光纤位置后,在输出端口光纤与边缘耦合器之间的光耦合损耗为3.52 dB,与参考值(3.30 dB)的误差仅为0.22 dB。【结论】文章验证了基于FP腔实现光纤与边缘耦合器高效对准的可行性。通过FP腔实现了对光纤与边缘耦合器间距以及光纤位移的测量,测量精度为亚微米级。文章还通过实验验证了基于FP腔的测距结果,仅需对光纤进行单次位置调整即可实现与边缘耦合器的高精度对准。

【Objective】Silicon photonic chips can achieve low-loss coupling with optical fibers through the on-chip silicon-based edge couplers(here in after referred to as edge couplers)integrated on the chips.In the packaging process of commercial silicon photonic chips,the demand for large-scale alignment of optical fibers and silicon photonic chips has raised higher requirements for the alignment efficiency of optical fibers and edge couplers.The research purpose of this paper is to optimize the alignment process between optical fibers and edge couplers based on the Fabry-Perot(FP)cavity formed between the optical fiber facet and the edge coupler facet.After measuring the distance between the optical fiber and the edge coupler in the axial direction of the fiber(represented as the x-axis in this article),high-precision alignment of the optical fiber and the edge coupler can be achieved by a single adjustment of the fiber position in this direction.【Methods】This paper studied the FP cavity structure formed between the optical fiber facet and the edge coupler facet.It also established the physical model between the reflection/transmission spectrum of the FP cavity and the distance between the facets.The optical fiber alignment platform is constructed to experimentally measure the distance between the facets through the FP cavity.Based on the distance measurement results,a single position adjustment of the optical fiber is realized along the axial direction of the optical fiber to achieve the alignment with the edge coupler.【Results】The deviation between the FP cavity length obtained in the experiment and the FP cavity length simulated by the ideal FP cavity model is less than 1μm.The measured displacement of the optical fiber is within the error range(±1μm)of the actual displacement.After adjusting the position of the optical fiber based on the distance measurement results,the optical coupling loss is 3.52 dB between the optical fiber and the edge coupler at the output port,and the error with the reference value(3.30 dB)is only 0.22 dB.【Conclusion】The work verifies the feasibility of achieving efficient alignment between optical fibers and edge couplers based on FP cavity.Through the FP cavity,the measurement accuracy of the distance between the optical fiber and the edge coupler is at the sub-micrometer level and the measurement accuracy of the optical fiber displacement is also at the sub-micrometer level.The experiments demonstrate that the high-precision alignment between the optical fiber and the edge coupler could be realized with only a single adjustment of fiber position according the measurement results obtained by the FP cavity.