The Heterodyne spectroscopy laboratory is dedicated to the development of techniques and equipment for millimeter-wave and Terahertz (THz) heterodyne spectroscopy. The laboratory is equipped with electronic transmitters and receivers for the range from 0.22 – 2.06 THz and several THz lasers (Quantum Cascade Lasers (QCLs)) in the range 2.7 – 4.7 THz. Coherent detectors (mixers) involve Schottky diode mixers and superconducting hot-electron bolometers. For beam characterization, several microbolometer cameras and scanning stages exist, as well as black body sources for radiometric calibration. For the integration of detectors, a microscope and a bonding machine are available. A wide range of microwave instrumentation is available for mixer characterization and spectroscopy, which involves spectrum analyzers and synthesizers up to 40 GHz, a network analyzer up to 13.5 Gigahertz (GHz), low noise RF amplifiers, as well as digital Fourier transform spectrometers.
There is a variety of Terahertz lasers available in the laboratory for the application in heterodyne spectroscopy, but also in gas phase and solid -tate spectroscopy. Both, in-house developed systems:
DC-excited CO2 lasers, continuous wave, wavelength 9 - 11 µm, 50 W peak power.
Several THz quantum-cascade lasers, wavelength 60-120 µm, up to 10 mW power, continuous-wave and pulsed)
and commercially available lasers:
RF-excited CO2 laser, continuous wave, wavelength 9 -11 µm, 40 W peak power.
IR diode lasers (continuous-wave and pulsed, 1.5 µm).
frequency stabilized CO2 laser system, continuous wave, wavelength 9 -11 µm, 40 W peak power, frequency stability < 1 MHz/hour, currently on loan at Karlsruhe Institute of Technology
All lasers, home-made as well as commercial ones, are equipped with control electronics and, where necessary, with vacuum or cryogenic equipment (mechanical cryocoolers for 4-300 K, 4 K dipsticks, magnetic field facilities up to 3 T , high-voltage power supplies, etc.). Furthermore, a beam-profile measurement setup for the wavelength range from 10 µm to 1000 µm is available.
