标题： 基于劈裂超晶格的光控纳米换能器用于监测吉赫兹表面声波振动 显示英文标题

标题： Optically-Controlled Nano-Transducers Based on Cleaved Superlattices for Monitoring Gigahertz Surface Acoustic Vibrations

摘要： 表面声波（SAWs）在表面以亚波长深度传递能量。 使用叉指换能器（IDTs）和光-声-光换能器（OAOTs），研究人员已经利用具有纳秒周期和微米定位深度的相干表面声波，用于各种应用。 然而，通过表面纳米图案化技术产生的先进OAOTs，将相干表面声波频率上限限制在100 GHz以下，这受到表面纳米图案的质量和间距等因素的制约，更不用说IDTs的电子带宽限制了。 在此背景下，本文提出了一种基于解理超晶格（SLs）的非常规光学控制纳米换能器作为替代解决方案。 为了证明其可行性，我们使用超快激光器在泵浦-探测配置下对由交替的AlxGa1-xAs和AlyGa1-yAs层组成的SLs进行了概念验证实验，这些层具有约70 nm的周期性，并沿着生长方向解理以产生周期性纳米结构表面。 由入射在解理表面上的激光束生成和检测的声学振动范围从40 GHz到70 GHz，对应于色散关系中的广义表面瑞利模式和体模式。 这项研究显示，除了表面声波外，解理SLs还提供了在GHz频率下观察表面滑动纵向和横向声波的潜力。 这种在纳米声学中使用这种非常规平台在100 GHz以下的概念验证演示，为未来实现亚太赫兹到太赫兹相干表面声波振动提供了机会，因为SLs可以以原子尺度的层宽和质量外延生长。 显示英文摘要

摘要： Surface acoustic waves (SAWs) convey energy at subwavelength depths along surfaces. Using interdigital transducers (IDTs) and opto-acousto-optic transducers (OAOTs), researchers have harnessed coherent SAWs with nanosecond periods and micrometer localization depth for various applications. However, the utilization of cutting-edge OAOTs produced through surface nanopatterning techniques has set the upper limit for coherent SAW frequencies below 100 GHz, constrained by factors such as the quality and pitch of the surface nanopattern, not to mention the electronic bandwidth limitations of the IDTs. In this context, unconventional optically-controlled nano-transducers based on cleaved superlattices (SLs) are here presented as an alternative solution. To demonstrate their viability, we conducted proof-of-concept experiments using ultrafast lasers in a pump-probe configuration on SLs made of alternating AlxGa1-xAs and AlyGa1-yAs layers with approximately 70 nm periodicity and cleaved along their growth direction to produce a periodic nanostructured surface. The acoustic vibrations, generated and detected by laser beams incident on the cleaved surface, span a range from 40 GHz to 70 GHz, corresponding to the generalized surface Rayleigh mode and bulk modes within the dispersion relation. This exploration shows that, in addition to SAWs, cleaved SLs offer the potential to observe surface-skimming longitudinal and transverse acoustic waves at GHz frequencies. This proof-of-concept demonstration below 100 GHz in nanoacoustics using such an unconventional platform offers opportunities for realizing sub-THz to THz coherent surface acoustic vibrations in the future, as SLs can be epitaxially grown with atomic-scale layer width and quality.