THz time-domain spectroscopy (TDS) is a promising tool for quality control purposes in industrial applications, but the high cost and the relatively large laser sources still make it difficult to use the full potential of the technology for a decent price. In this work, a THz TDS system, which uses a commercially available Fabry–Perot laser diode emitting at 1550 nm, is presented. By dispersion compensation, pulses with a duration of 544 fs were generated, resulting in THz radiation with a bandwidth of 1.4 THz and a peak dynamic range of 56 dB with state-of-the-art ErAs:In(Al)GaAs photoconducting antennas. These results are compared with those of a conventional and expensive fiber laser system with a 90 fs pulse duration.

After 20 years of terahertz cross-correlation spectroscopy (THz-CCS), the performance of the systems has been improved to practical relevance by reaching a bandwidth of ~2 THz. For the development of high-performance THz-CCS systems, it is necessary to get a deeper knowledge of the signal generation from incoherent light sources. In this work, the bandwidth, dynamic range, and peak-to-peak amplitude of a THz-CCS systems using a superluminescent diode as light source and a programmable optical filter for spectral shaping was investigated to obtain a better understanding of the relationship between the optical spectrum and the generated terahertz spectrum. By a periodic structuring of the continuous optical spectrum, an enhancement of the peak dynamic range of more than 10 dB was achieved with a bandwidth of 1.6 THz. The experimental results are confirmed by numerical simulations.