标题： 用于宽频带片上光斑尺寸转换的抛物面介质反射器 显示英文标题

标题： Parabolic dielectric reflector for extreme on-chip spot-size conversion with broad bandwidth

摘要： 光斑尺寸转换器对于在不同尺寸的波导之间高效耦合光至关重要。 虽然绝热锥形结构适用于较小的尺寸差异，但在需要将集成波导与自由空间光束耦合时，扩张因子约为x100的情况下，它们变得不切实际地长。 在此情形下可以使用倏逝波耦合器和布拉格偏转器，但它们的运行带宽本质上是有限的。 在这里，我们提出了一种基于抛物线介质界面的解决方案，该界面将光从0.5微米宽的波导耦合到285微米宽的波导，即扩张因子为x570。 我们实验上展示了超过380纳米的前所未有的带宽，插入损耗低于0.35分贝。 此外，我们还提供了用于任意扩张因子的此类抛物线光斑尺寸转换器的设计分析表达式。 显示英文摘要

摘要： Spot-size converters are key for efficient coupling of light between waveguides of different sizes. While adiabatic tapers are well suited for small size differences, they become impractically long for expansion factors around x100 which are often required when coupling integrated waveguides and free-space beams. Evanescent couplers and bragg deflectors can be used in this scenario, but their operation is inherently limited in bandwidth. Here we propose a solution based on a parabolic dielectric interface that couples light from a 0.5 um-wide waveguide to a 285 um-wide waveguide, i.e. an expansion factor of x570. We experimentally demonstrate an unprecedented bandwidth of more than 380 nm with insertion losses below 0.35 dB. We furthermore provide analytical expressions for the design of such parabolic spot-size-converters for arbitrary expansion factors.