Detection of small defects by THz-waves for non-destructive testing in dielectric layered structures

Non-destructing testing of dielectric materials by mm electromagnetic waves has been implemented since reliable sources of microwave power and detectors were developed. However, small defect scatters effectively only when its size is comparable or greater than a wavelength of the testing signal. Significant progress in terahertz and sub-mm techniques development made possible the development of non-destructive testing systems for small defects in dielectric layered structures detection. Up to date a time-domain THz spectroscopy (THz-TDS) has been the most popular method for scanning dielectric layered structures and finding inhomogenities in transparent dielectric layered structures [1,2]. Taking into account that THz-TDS systems are very expensive and measurements with following data processing are time-consuming a new polarization-dependent method for defect detection is considered.