Figure 6: Terahertz spectroscopy using the homogeneous broadband terahertz QCL.
From: Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation
(a) Transmission spectrum of a semi-insulating GaAs etalon sample (625 ± 25 μm) using a homogeneous broadband terahertz QCL source under RF modulation at 6.1977 GHz and 25 dBm. The blue curve is a fit using a transfer matrix algorithm. The dashed vertical line shows the strong water absorption. (b) Spectral identification for the ammonia gas (NH3) using the homogeneous broadband terahertz QCL. The black spectrum is measured with a plastic bottle filled with air, and the flipped red spectrum is obtained with the same bottle filled with ammonia gas. Both spectra are normalized. The blue lines represent the absorption of ammonia gas given by the HITRAN database.
