Margheri Giancarlo, Del Rosso Tommaso
Institute for Complex Systems of National Council of Researches of Italy, Separate Location of Sesto Fiorentino, Via Madonna del Piano, 50019 Sesto Fiorentino, Florence, Italy.
Department of Physics, Pontifícia Universidade Católica do Rio de Janeiro, Rua Marques de São Vicente, Rio de Janeiro 22451-900, Brazil.
Micromachines (Basel). 2023 Oct 18;14(10):1939. doi: 10.3390/mi14101939.
THz radiation has assumed great importance thanks to the efforts in the development of technological tools used in this versatile band of the electromagnetic spectrum. Here, we propose a reflective biprism device with wavelength-independent long-focusing performances in the THz band by exploiting the high thermo-mechanical deformation of the elastomer polydimethylsiloxane (PDMS). This deformation allows for achieving significant optical path modulations in the THz band and effective focusing. The surface of a PDMS layer is covered with a gold thin film acting as a heater thanks to its absorption of wavelengths below ~500 nm. An invariance property of the Fresnel integral has been exploited to experimentally verify the THz performances of the device with an ordinary visible laser source, finding excellent agreement with the theoretical predictions at 1 and 3 THz. The same property also allowed us to experimentally verify that the reflective biprism focus has a longitudinal extension much greater than that exhibited by a benchmark convex cylindrical mirror with the same optical power. The device is thermo-mechanically stable up to a heating power of 270 mW, although it might be potentially exploited at higher powers with minor degradation of the optical performances.
由于在电磁频谱这一通用频段所使用的技术工具开发方面的努力，太赫兹辐射已变得极为重要。在此，我们提出一种反射双棱镜装置，通过利用弹性体聚二甲基硅氧烷（PDMS）的高热机械变形，在太赫兹频段实现与波长无关的长焦距性能。这种变形使得在太赫兹频段能够实现显著的光程调制和有效聚焦。PDMS层的表面覆盖有一层金薄膜，由于其对波长低于约500nm的光的吸收而起到加热器的作用。利用菲涅耳积分的不变性，用普通可见激光源对该装置的太赫兹性能进行了实验验证，发现在1太赫兹和3太赫兹时与理论预测结果高度吻合。同样的特性还使我们能够通过实验验证，反射双棱镜焦点的纵向延伸远大于具有相同光焦度的基准凸柱面镜所呈现的纵向延伸。该装置在加热功率高达270mW时热机械性能稳定，尽管在更高功率下使用时可能会导致光学性能略有下降，但仍具有潜在的应用价值。
