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Increasing the THz-QTDS Bandwidth from 1.7 to 2.5 THz Through Optical Feedback

: Rehn, A.; Kohlhaas, R.; Globisch, B.; Balzer, J.C.


Journal of infrared, millimeter, and terahertz waves 40 (2019), Nr.11-12, S.1103-1113
ISSN: 1866-6892
ISSN: 1866-6906
Fraunhofer HHI ()

We demonstrate that the bandwidth of a terahertz (THz) quasi time-domain spectroscopy (QTDS) system can be increased by controlled optical feedback into the multimode laser diode. The THz spectral broadening correlates well with the broadening of the optical spectrum. Our results show that the phase of the feedback does not affect the optical or THz bandwidth in general, although certain combinations of feedback power and phase can create additional high-frequency components in the THz spectrum, which are not present otherwise. For the optimal combination of feedback power and phase, the bandwidth of the THz QTDS system is increased from 1.7 to 2.5 THz.