Wells Brian M, Tripp Joseph F, Krupa Nicholas W, Rittenberg Andrew J, Williams Richard J
Department of Physics, University of Hartford, West Hartford, CT 06117, USA.
CT State Community College, Norwalk, CT 06854, USA.
Sensors (Basel). 2024 Oct 10;24(20):6519. doi: 10.3390/s24206519.
We present a sensor that utilizes a modified single-frequency split beam metasurface reflector to measure the refractive index of materials ranging from one to three. Samples are placed into a cavity between a PCB-etched dielectric and a reflecting ground plane. It is illuminated using a 10.525 GHz free-space transmit horn with reflecting angles measured by sweeping a receiving horn around the setup. Predetermined changes in measured angles determined through simulations will coincide with the material's index. The sensor is designed using the Fourier transform method of array synthesis and verified with FEM simulations. The device is fabricated using PCB milling and 3D printing. The quality of the sensor is verified by characterizing 3D printed dielectric samples of various infill percentages and thicknesses. Without changing the metasurface design, the sensing performance is extended to accommodate larger sample thicknesses by including a modified 3D printed fish-eye lens mounted in front of the beam splitter; this helps to exaggerate changes in reflected angles for those samples. All the methods presented are in agreement and verified with single-frequency index measurements using Snell's law. This device may offer a viable alternative to traditional index characterization methods, which often require large sample sizes for single-frequency measurements or expensive equipment for multi-frequency parameter extraction.
我们展示了一种传感器，它利用经过改进的单频分束超表面反射器来测量折射率范围在1到3之间的材料。样品放置在印刷电路板蚀刻电介质与反射接地平面之间的空腔中。使用一个10.525 GHz的自由空间发射喇叭对其进行照射，并通过在装置周围扫描接收喇叭来测量反射角。通过模拟确定的测量角度的预定变化将与材料的折射率相符。该传感器采用阵列合成的傅里叶变换方法进行设计，并通过有限元模拟进行验证。该装置采用印刷电路板铣削和3D打印制造。通过对各种填充百分比和厚度的3D打印电介质样品进行表征，验证了传感器的质量。在不改变超表面设计的情况下，通过在分束器前面安装一个经过改进的3D打印鱼眼透镜，将传感性能扩展到能够适应更大的样品厚度；这有助于放大那些样品反射角的变化。所提出的所有方法均一致，并通过使用斯涅尔定律的单频折射率测量进行了验证。该装置可能为传统折射率表征方法提供一种可行的替代方案，传统方法通常需要大尺寸样品进行单频测量，或者需要昂贵的设备来提取多频参数。
