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Measurements of THz pulse signals based on superconducting hot electron bolometer detectors

A system to detect the terahertz (THz) pulse signals has been studied based on the superconducting NbN hot electron bolometer (HEB) detectors, which has the noise equivalent power (NEP) of 9×10-12 W/√Hz, together with a Fourier transform spectrometer (FTS). The detector has been driven by an easily adjustable microwave source to its best bias working point, and its output shown a linear relationship with the incident THz power. Comparing with the FTS system with a commercial semiconducting bolometer detector with same sensitivity and working at low temperature (4.2 K), it has been found that our system worked well to measure the spectra of the THz pulse signals generated from a quantum cascade laser (QCL).