Wang Cheng, Zhang Mian, Stern Brian, Lipson Michal, Lončar Marko
Opt Express. 2018 Jan 22;26(2):1547-1555. doi: 10.1364/OE.26.001547.
Since the emergence of optical fiber communications, lithium niobate (LN) has been the material of choice for electro-optic modulators, featuring high data bandwidth and excellent signal fidelity. Conventional LN modulators however are bulky, expensive and power hungry, and cannot meet the growing demand in modern optical data links. Chip-scale, highly integrated, LN modulators could offer solutions to this problem, yet the fabrication of low-loss devices in LN thin films has been challenging. Here we overcome this hurdle and demonstrate monolithically integrated LN electro-optic modulators that are significantly smaller and more efficient than traditional bulk LN devices, while preserving LN's excellent material properties. Our compact LN electro-optic platform consists of low-loss nanoscale LN waveguides, micro-ring resonators and miniaturized Mach-Zehnder interferometers, fabricated by directly shaping LN thin films into sub-wavelength structures. The efficient confinement of both optical and microwave fields at the nanoscale dramatically improves the device performances featuring a half-wave electro-optic modulation efficiency of 1.8 V∙cm while operating at data rates up to 40 Gbps. Our monolithic LN nanophotonic platform enables dense integration of high-performance active components, opening new avenues for future high-speed, low power and cost-effective communication networks.
自光纤通信出现以来，铌酸锂（LN）一直是电光调制器的首选材料，具有高数据带宽和出色的信号保真度。然而，传统的LN调制器体积庞大、价格昂贵且功耗大，无法满足现代光数据链路中不断增长的需求。芯片级、高度集成的LN调制器可以为这个问题提供解决方案，但在LN薄膜中制造低损耗器件一直具有挑战性。在这里，我们克服了这一障碍，展示了单片集成的LN电光调制器，其尺寸比传统的块状LN器件小得多，效率更高，同时保留了LN优异的材料特性。我们紧凑的LN电光平台由低损耗纳米级LN波导、微环谐振器和小型化马赫曾德尔干涉仪组成，通过将LN薄膜直接成型为亚波长结构来制造。在纳米尺度上对光场和微波场的有效限制显著提高了器件性能，在高达40 Gbps的数据速率下工作时，半波电光调制效率为1.8 V∙cm。我们的单片LN纳米光子平台实现了高性能有源组件的密集集成，为未来高速、低功耗和经济高效的通信网络开辟了新途径。
