Towards Detection of OH Line at 3.5 THz Using a HEB Mixer and a Distributed Feedback Quantum Cascade Laser

摘要

We report the demonstration of a heterodyne receiver for detection of OH lines at 3.5 THz. The receiver uses a superconducting NbN hot electron bolometer integrated with a tight winding spiral antenna as mixer and a THz distributed feedback quantum cascade laser operating at 3.42 THz as local oscillator. We measured a double sideband receiver noise temperature of 2100 K at the optimum local oscillator power of 290 nW. This noise temperature can be further reduced to 1000 K if we correct the loss due to the use of an uncoated lens, and the losses of the window and the air. We also demonstrate that the improved, single spot beam of the THz QCL can easily pump the HEB mixer. Therefore, the combination of a HEB and such a DFB QCL can in principle be used to detect an OH line at 3.5 THz. However, a high input power of several watts 1 needed to operate the QCL at an L-He cryostat poses a big challenge to the receiver stability.