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arXiv · 2311.05837

High-efficiency edge couplers enabled by vertically tapering on lithium-niobate photonic chips

Di Jia·Qiang Luo·Chen Yang·Rui Ma·Xuanyi Yu·Feng Gao·Qifan Yang·Fang Bo·Guoquan Zhang·Jingjun Xu
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Abstract

In the past decade, photonic integrated circuits (PICs) based on thin-film lithium niobate (TFLN) have advanced in various fields, including optical communication, nonlinear photonics, and quantum optics. A critical component is an efficient edge coupler connecting PICs to light sources or detectors. Here, we propose an innovative edge coupler design with a wedge-shaped TFLN waveguide and a silicon oxynitride (SiON) cladding. Experimental results show that the coupling loss between the TFLN PIC and a 3-{\mu}m mode field diameter (MFD) lensed fiber is low at 1.52 dB/facet, with the potential for improvement to 0.43 dB/facet theoretically. The coupling loss between the edge coupler and a UHNA7 fiber with an MFD of 3.2 {\mu}m is reduced to 0.92 dB/facet. This design maintains robust fabrication and alignment tolerance. Importantly, the minimum linewidth of the TFLN waveguide of the coupler (600 nm) can be easily achieved using foundry-available i-line stepper lithography. This work benefits the development of TFLN integrated platforms, such as on-chip electro-optic modulators, frequency comb generation, and quantum sensors.

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Di Jia, Qiang Luo, Chen Yang, Rui Ma, Xuanyi Yu, Feng Gao, Qifan Yang, Fang Bo, Guoquan Zhang, Jingjun Xu. 2023-11-10. High-efficiency edge couplers enabled by vertically tapering on lithium-niobate photonic chips. https://arxiv.org/abs/2311.05837

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