Continuous wave terahertz receivers with 4.5 THz bandwidth and 112 dB dynamic range

Abstract

We present photomixers made of iron doped indium gallium arsenide (InGaAs:Fe) as broadband receivers in optoelectronic continuous wave (cw) terahertz (THz) systems. InGaAs:Fe shows higher resistivity and shorter carrier lifetimes compared to the state-of-the-art low-temperature-grown material. These improved material properties translate into an improved frequency response and lower noise level of the InGaAs:Fe photomixers. We were able to measure a bandwidth of 4.5 THz with a peak dynamic range of 112 dB at 30 mW laser excitation around 1550 nm. To the best of our knowledge, these are record high values for cw THz spectroscopy. Furthermore we achieved an increased dynamic range by up to 10 dB for frequencies above 1 THz compared to state-of-the-art photomixing receivers. These improvements enable faster and more precise spectroscopy with higher bandwidth. In industrial non-destructive testing, the measurement rate may be increased by a factor of ten posing a valuable contribution to inline process monitoring.