Tailoring the interaction between light and sound has opened new possibilities in photonic integrated circuits (PICs) that range from achieving quantum control of light to high-speed information processing. However, the actuation of sound waves in Si PICs usually requires integration of a piezoelectric thin film. Lead zirconate titanate (PZT) is a promising material due to its strong piezoelectric and electromechanical coupling coefficient. Unfortunately, the traditional methods to grow PZT on silicon are detrimental for photonic applications due to the presence of an optical lossy intermediate layer. In this work, we report integration of a high quality PZT thin film on a silicon-on-insulator (SOI) photonic chip using an optically transparent buffer layer. We demonstrate acousto-optic modulation in silicon waveguides with the PZT actuated acoustic waves. We fabricate interdigital transducers (IDTs) on the PZT film with a contact photolithography and electron-beam lithography to generate the acoustic waves in MHz and GHz ranges, respectively. We obtain a V_πL ∼ 3.35 V·cm at 576 MHz from a 350 nm thick gold (Au) IDT with 20 finger-pairs. After taking the effect of mass-loading and grating reflection into account, we measured a V_πL ∼ 3.60 V·cm at 2 GHz from a 100 nm thick aluminum (Al) IDT consisting of only four finger-pairs. Thus, without patterning the PZT film nor suspending the device, we obtained figures-of-merit comparable to state-of-the-art modulators based on SOI, making it a promising candidate for a broadband and efficient acousto-optic modulator for future integration.

中文翻译：

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PZT 驱动声波在硅光子学中的光调制

调整光和声音之间的相互作用为光子集成电路 (PIC) 开辟了新的可能性，从实现光的量子控制到高速信息处理。然而，Si PIC 中的声波驱动通常需要集成压电薄膜。锆钛酸铅 (PZT) 是一种很有前途的材料，因为它具有很强的压电和机电耦合系数。不幸的是，由于存在光损耗中间层，传统的在硅上生长 PZT 的方法不利于光子应用。在这项工作中，我们报告了使用光学透明缓冲层在绝缘体上硅 (SOI) 光子芯片上集成高质量 PZT 薄膜。我们用 PZT 驱动的声波演示了硅波导中的声光调制。我们通过接触光刻和电子束光刻在 PZT 薄膜上制造叉指换能器 (IDT)，以分别生成 MHz 和 GHz 范围内的声波。我们得到一个V _π L ∼ 3.35 V·cm，频率为 576 MHz，来自具有 20 个手指对的 350 nm 厚金 (Au) IDT。考虑到质量负载和光栅反射的影响后，我们在 2 GHz 时从仅包含四个指对的 100 nm 厚铝 (Al) IDT测量了V _π L ∼ 3.60 V·cm。因此，无需对 PZT 薄膜进行图案化，也无需悬挂设备，我们获得了可与基于 SOI 的最先进调制器相媲美的品质因数，使其成为未来集成的宽带和高效声光调制器的有希望的候选者.