Optical communication systems increasingly require electro-optical modulators that deliver high modulation speeds across a large optical bandwidth with a small device footprint and a CMOS-compatible fabrication process. Although silicon photonic modulators based on transparent conducting oxides (TCOs) have shown promise for delivering on these requirements, modulation speeds to date have been limited. Here, we describe the design, fabrication, and performance of a fast, compact electroabsorption modulator based on TCOs. The modulator works by using bias voltage to increase the carrier density in the conducting oxide, which changes the permittivity and hence optical attenuation by almost 10 dB. Under bias, light is tightly confined to the conducting oxide layer through nonresonant epsilon-near-zero (ENZ) effects, which enable modulation over a broad range of wavelengths in the telecommunications band. Our approach features simple integration with passive silicon waveguides, the use of stable inorganic materials, and the ability to modulate both transverse electric and magnetic polarizations with the same device design. Using a 4-μm-long modulator and a drive voltage of $2{\mathrm{V}}_{pp}$, we demonstrate digital modulation at rates of 2.5 Gb/s. We report broadband operation with a 6.5 dB extinction ratio across the 1530–1590 nm band and a 10 dB insertion loss. This work verifies that high-speed ENZ devices can be created using conducting oxide materials and paves the way for additional technology development that could have a broad impact on future optical communications systems.

中文翻译：

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ε近零硅光子调制器的千兆赫兹速度运行

光通信系统越来越需要电光调制器，该电光调制器可在较大的光带宽上以较小的设备占地面积和CMOS兼容制造工艺提供高调制速度。尽管基于透明导电氧化物（TCO）的硅光子调制器已显示出满足这些要求的希望，但迄今为止，调制速度受到了限制。在这里，我们描述了基于TCO的快速，紧凑的电吸收调制器的设计，制造和性能。调制器通过使用偏置电压来增加导电氧化物中的载流子密度，从而改变介电常数，从而使光衰减几乎增加10 dB。在偏压下，光会通过非共振ε-接近零（ENZ）效应被严格限制在导电氧化物层中，它们能够在电信频段的宽广波长范围内进行调制。我们的方法具有与无源硅波导进行简单集成，使用稳定的无机材料以及使用相同的器件设计来调制横向电极化和磁极化的能力。使用4μm长的调制器和驱动电压为$\mathrm{2个}{\mathrm{伏特}}_{pp}$，我们以2.5 Gb / s的速率演示了数字调制。我们报告说宽带工作在1530–1590 nm波段的消光比为6.5 dB，插入损耗为10 dB。这项工作验证了可以使用导电氧化物材料创建高速ENZ器件，并为可能对未来的光通信系统产生广泛影响的其他技术开发铺平了道路。