A 4.7 THz HEB/QCL heterodyne receiver for STO-2

We report on a 4.7 THz heterodyne receiver being developed to fly on the Stratospheric Terahertz Observatory (STO-2) balloon platform. The receiver is based on a single pixel hot electron bolometer (HEB) mixer pumped by a 4.7 THz 3
^rd
order distributed feedback quantum cascade laser (QCL) as local oscillator and is designed for high resolution spectroscopy of the astronomically important neutral oxygen (OI) line at 4.745 THz. We describe the expected receiver performance and outline novel approaches to QCL amplitude and frequency/phase stabilization.