Electro-optic (EO) modulators rely on the interaction of optical and electrical signals with second-order nonlinear media. For the optical signal, this interaction can be strongly enhanced using dielectric slot–waveguide structures that exploit a field discontinuity at the interface between a high-index waveguide core and the low-index EO cladding. In contrast to this, the electrical signal is usually applied through conductive regions in the direct vicinity of the optical waveguide. To avoid excessive optical loss, the conductivity of these regions is maintained at a moderate level, thus leading to inherent RC limitations of the modulation bandwidth. In this paper, we show that these limitations can be overcome by extending the slot–waveguide concept to the modulating radio-frequency (RF) signal. Our device combines an RF slotline that relies on ${\rm{BaTi}}{{\rm{O}}_3}$ as a high-k dielectric material with a conventional silicon photonic slot waveguide and a highly efficient organic EO cladding material. In a proof-of-concept experiment, we demonstrate a 1 mm long Mach–Zehnder modulator that offers a 3 dB bandwidth of 76 GHz and a 6 dB bandwidth of 110 GHz along with a small $\pi$ voltage of 1.3 V (${U_\pi}L = {1.3}\;{\rm{V}}\;{\rm{mm}}$). We further demonstrate the viability of the device in a data-transmission experiment using four-state pulse-amplitude modulation (PAM4) at line rates up to 200 Gbit/s. Our first-generation devices leave vast room for further improvement and may open an attractive route towards highly efficient silicon photonic modulators that combine sub-1 mm device lengths with sub-1 V drive voltages and modulation bandwidths of more than 100 GHz.

中文翻译：

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混合电光调制器，结合了硅光子缝隙波导和高k射频缝隙线

电光（EO）调制器依赖于光和电信号与二阶非线性介质的相互作用。对于光信号，可以使用电介质缝隙-波导结构大大增强这种相互作用，该结构利用高折射率波导芯和低折射率EO包层之间的界面处的场不连续性。与此相反，电信号通常通过光波导直接附近的导电区域施加。为避免过多的光损耗，这些区域的电导率应保持在中等水平，从而导致固有的RC调制带宽的限制。在本文中，我们表明可以通过将缝隙-波导概念扩展到调制射频（RF）信号来克服这些限制。我们的设备将依靠$ {\ rm {BaTi}} {{\ rm {O}} _ 3} $作为高k介电材料的RF缝线与常规的硅光子缝隙波导和高效有机EO包层材料相结合。在验证的概念的实验中，我们证明1毫米长马赫-策德尔调制器，其提供76千兆赫的3dB带宽和110千兆赫的具有小的沿6分贝带宽$ \ PI $为1.3V的电压（$ {U_ \ pi} L = {1.3} \; {\ rm {V}} \ ;; {\ rm {mm}} $）。我们还将在高达200 Gbit / s的线速下使用四态脉冲幅度调制（PAM4）的数据传输实验中证明该设备的可行性。我们的第一代设备为进一步的改进留有广阔的空间，并可能为通向高效的硅光子调制器开辟一条诱人的途径，该调制器将1mm以下的设备长度与1V以下的驱动电压以及超过100 GHz的调制带宽结合在一起。