Online terahertz thickness determination of sub-wavelength layers at kilohertz measurement rates

We present an online layer-thickness measurement system capable of assessing multiple sub-wavelength layers at a data rate of 1.6 kHz. Combining an ultrafast terahertz time-domain spectroscopy engine based on electronically controlled optical sampling (ECOPS) with a highly efficient CPU-based evaluation algorithm, an industry-ready measurement system is realized. To evaluate the performance, we quantify the thickness of multilayer paint samples on aluminum substrates.