Ingar Romero Alonso, Mukherjee Amlan Kusum, Fernandez Olvera Anuar, Méndez Aller Mario, Preu Sascha
Department of Electrical Engineering and Information Technology, Technical University of Darmstadt, 64283, Darmstadt, Germany.
Nat Commun. 2021 Dec 7;12(1):7091. doi: 10.1038/s41467-021-27264-x.
The resolution along the propagation direction of far field imagers can be much smaller than the wavelength by exploiting coherent interference phenomena. We demonstrate a height profile precision as low as 31 nm using wavelengths between 0.375 mm and 0.5 mm (corresponding to 0.6 THz-0.8 THz) by evaluating the Fabry-Pérot oscillations within surface-structured samples. We prove the extreme precision by visualizing structures with a height of only 49 nm, corresponding to 1:7500 to 1:10000 vacuum wavelengths, a height difference usually only accessible to near field measurement techniques at this wavelength range. At the same time, the approach can determine thicknesses in the centimeter range, surpassing the dynamic range of any near field measurement system by orders of magnitude. The measurement technique combined with a Hilbert-transform approach yields the (optical) thickness extracted from the relative phase without any extraordinary wavelength stabilization.
通过利用相干干涉现象，远场成像仪沿传播方向的分辨率可以比波长小得多。通过评估表面结构化样品内的法布里-珀罗振荡，我们使用0.375毫米至0.5毫米（对应于0.6太赫兹至0.8太赫兹）的波长展示了低至31纳米的高度轮廓精度。我们通过可视化仅49纳米高的结构证明了这种极高的精度，该高度对应于1:7500至1:10000的真空波长，这种高度差通常只有在该波长范围内的近场测量技术才能实现。同时，该方法可以确定厘米范围内的厚度，比任何近场测量系统的动态范围高出几个数量级。该测量技术与希尔伯特变换方法相结合，无需任何特殊的波长稳定即可从相对相位中提取（光学）厚度。
