Acousto-optical devices, such as modulators, filters, or deflectors, implement a simple and effective way of light modulation and signal-processing techniques. However, their operation wavelengths are restricted to the visible and near-infrared frequency regions due to a quadratic decrease of the efficiency of acousto-optical interactions with increasing wavelength. At the same time, almost all materials with a high value of the acousto-optic figure of merit are nontransparent at wavelengths longer than 5 µm, while the transparent materials possess a significantly lower acousto-optic figure of merit. Here, we propose and demonstrate by calculations how these limitations can be overcome using specially designed planar semiconductor structures that support electromagnetic modes strongly coupled to the incident light in the Otto configuration. Such an approach can be used for an efficient acousto-optical device operating in the mid-infrared range of 8–14 µm. An acoustic wave excited by a piezoelectric transducer in a semiconductor prism is utilized to modulate the coupling coefficient of the incident light to the guided mode of the semiconductor structure, which results in up to 100% modulation of the transmitted light at a spatial scale less than the ultrasound wavelength. It allows the utilization of acoustic waves with a short decay distance, and therefore, it provides a unique possibility to achieve an efficient acousto-optical modulation at frequencies about 1 GHz, which are unreachable for traditional acousto-optics.

中文翻译：

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支持引导模式的平面半导体结构在中红外光谱范围内的高效声光调制

诸如调制器，滤波器或偏转器之类的声光设备实现了一种简单有效的光调制和信号处理技术。但是，由于声光相互作用的效率随波长的增加呈二次下降，因此它们的工作波长仅限于可见光和近红外频率区域。同时，几乎所有具有高声光品质因数值的材料在波长大于5 µ时都是不透明的 m，而透明材料具有明显较低的声光品质因数。在这里，我们提出并通过计算演示如何使用特殊设计的平面半导体结构克服这些限制，这些平面半导体结构支持与Otto配置中的入射光强耦合的电磁模式。这种方法可用于在8–14 µ的中红外范围内运行的高效声光设备 米 半导体棱镜中的压电换能器激发的声波用于将入射光的耦合系数调制为半导体结构的导模，从而导致在小于20％的空间范围内对透射光进行高达100％的调制。超声波波长。它允许利用短衰减距离的声波，因此，它提供了一种独特的可能性，可以在大约1 GHz的频率上实现有效的声光调制，这是传统声光无法实现的。