Lithography-friendly spot-size converter for thin-film lithium niobate photonics

【摘要】 Conventional spot-size converters for thin-film lithium niobate require sub-100-nm features incompatible with standard dry etching. A 300-nm-lithography-compatible edge-coupled spot-size converter achieves a 3.5-μm mode field diameter at 1550 nm. With a matched single-mode fiber, it exhibits a single-facet coupling loss as low as 0.90 dB, average 1.0 dB,and alignment tolerances of ±1.1 μm vertically and ±1.45 μm horizontally. Monolithic integration with a 64-GHz modulator enables error-free 200-Gbps PAM-4 transmission with a transmitter dispersion eye closure for quaternary modulation of 2.39 dB, satisfying IEEE 802.3 dj. This provides a practical, process-friendly fiber–chip interface for platforms lacking advanced nanofabrication.更多还原

【Abstract】 Conventional spot-size converters for thin-film lithium niobate require sub-100-nm features incompatible with standard dry etching. A 300-nm-lithography-compatible edge-coupled spot-size converter achieves a 3.5-μm mode field diameter at 1550 nm. With a matched single-mode fiber, it exhibits a single-facet coupling loss as low as 0.90 dB, average 1.0 dB,and alignment tolerances of ±1.1 μm vertically and ±1.45 μm horizontally. Monolithic integration with a 64-GHz modulator enables error-free 200-Gbps PAM-4 transmission with a transmitter dispersion eye closure for quaternary modulation of 2.39 dB, satisfying IEEE 802.3 dj. This provides a practical, process-friendly fiber–chip interface for platforms lacking advanced nanofabrication.更多还原