Comparison of the Performance of State-of-the-Art Photoconductive Receivers for Terahertz Photonic Spectrum Analysers

With the increased interest in Terahertz applications and technologies there is a growing demand of new and improved transmitters. Spectrum analyzers are frequently used to characterise the spectral purity of transmitters. The Terahertz range state-of-the-art electronic spectrum analyzers are limited in terms of frequency coverage and are very expensive. In this article we present an alternative: photonic spectrum analysers based on the optical downconversion of continuous-wave lasers and photoconductive receivers. We compare the performance of two state-of-the-art photoconductive receivers in terms of their spectral roll-off and the displayed average noise level. We conclude with a comparison of the displayed average noise level of the photonic spectrum analyser to that of an electronic system employing extender modules.