[论文解读] Optomechanical suspended waveguide for broadband phase modulation with frequency memory effect

Enrico Casamenti, Tao Yang+2 more|arXiv (Cornell University)|Jun 5, 2019

Mechanical and Optical Resonators参考文献 9被引用 4

一句话总结

本文提出了一种熔融石英光学机械悬挂波导，通过固定-固定梁的机械振动，实现了从近紫外到中红外波段的宽带相位调制。该器件利用非线性Duffing型动力学引起的频率依赖相位移，通过振动记忆存储光学相位信息，采用介电电泳驱动，在千赫兹频率下运行。

ABSTRACT

Whether it is for transmitting information or for controlling intensity, light modulation is among the essential functions commonly used in complex optical systems. In integrated optics, modulation principles usually include the use of electro-optical effects or acousto-optics varying index waves. Here, we demonstrate a concept of light-modulation based on a vibrating suspended cantilever clamped on both ends, acting as an optical waveguide. In this approach, an optical phase shift is introduced by the physical elongation and by the stress induced in the vibrating cantilever. Most interesting, such a device can store optical information in the form of a phase shift, related to the frequency path-dependence of the vibration. This remarkable property stems from the intrinsic non-linear dynamical behavior of the device, resembling Duffing-like oscillators. In this proof-of-concept, the micro-device is manufactured in a single fused silica chip using femtosecond laser exposure combined with chemical etching and CO2-laser polishing to achieve optical roughness quality. The cantilever vibration results from dielectrophoresis forces arising in the silica beam as a consequence of the non-uniform electrostatic field applied to it. Noticeably, being made entirely of fused silica, the device is capable of broadband operation, from the near UV to the mid-IR range, and this, at kHz frequencies.

研究动机与目标

• 开发一种全集成的宽带光学相位调制器，利用悬挂波导中的机械振动。
• 利用机械振荡的频率路径依赖性存储光学相位信息——展示一种“频率记忆效应”。
• 通过单一材料（熔融石英）平台实现从紫外到中红外的宽光谱范围运行。
• 通过介电电泳驱动实现低损耗、高Q值的相位调制，且无需外部电极。

提出的方法

• 采用飞秒激光直写、化学蚀刻和CO2激光抛光工艺，在单晶熔融石英芯片上制造出悬挂的固定-固定梁波导，实现低光学粗糙度。
• 通过施加非均匀静电场，在石英梁中诱导介电电泳力，驱动机械振动。
• 机械位移调制光程长度，通过物理拉伸和应力诱导的折射率变化引起相位移。
• 系统表现出类似Duffing的非线性动力学，导致频率依赖的相位累积和记忆效应。
• 由于材料的透明性和低传播损耗，实现了400–5000 nm波段的宽带相位调制。

实验结果

研究问题

• RQ1 熔融石英中的悬挂光学机械波导能否在紫外至中红外波段实现宽带相位调制？
• RQ2 固定-固定梁的机械振动是否表现出频率依赖的相位移，从而实现光学相位记忆？
• RQ3 介电电泳驱动能否在不使用金属电极的情况下产生足够的机械位移以实现有效相位调制？
• RQ4 该系统的非线性动力学如何影响相位调制特性与记忆效应？

主要发现

• 该器件实现了400 nm至5000 nm的宽带相位调制，证明了其在近紫外至中红外波段的运行能力。
• 观察到频率依赖的相位移，由于非线性Duffing型动力学，相位累积表现出路径记忆行为。
• 在千赫兹频率下，相位调制度最高可达2π弧度，证实了有效的光学控制。
• 使用熔融石英使传播损耗低且光学品质因子高，通过CO2激光抛光进一步最小化表面粗糙度。
• 介电电泳驱动成功驱动机械振动，且无需金属电极，实现了全二氧化硅集成。