Research on measuring the thickness of multi-layer non-metallic materials based on sparse deconvolution method

In this study, the sparse deconvolution method is introduced to enhance the terahertz technique’s ability to measure the thickness of multilayered nonmetallic materials. Measurements were conducted using a terahertz time-domain spectrometer with a frequency range of 0.2-3THz. The effectiveness of the sparse deconvolution method was validated through simulation experiments, with the simulation results indicating a minimum resolvable time of 0.1333333 ps. The experimental analysis demonstrated that the sparse deconvolution method effectively distinguished the air layer signals in the sample and accurately identified and differentiated the signals representing a 25 μm standard film with a time interval of 0.2 ps. Comparisons revealed that the thickness measurement error of the sparse deconvolution method is less than 2%, which is significantly lower than the error value of the frequency domain wavelet deconvolution (FWDD) method. The sparse deconvolution method can effectively improve the accuracy of thickness measurements of multi-layer non-metallic materials.