Abstract
We have found a modulation-limited behavior of interferometric THz spectra in the one-dimensional multilayer structures making up high/low refractive index material periods. These modulation-limited THz spectra are based on the fact that the degree of THz pulse broadening decreases with increasing the number of periods because some time-delayed and multiple reflected THz pulses are in-phase or out-of-phase. THz pulse broadening phenomenon can be expressed by a simple equation. The knowledge of spectral detail of THz pulses may improve the understanding and fabrication of THz multilayer structures, applicable for THz waveform synthesis.