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Dual polarization THz time domain spectroscopy system

In many THz Time Domain Spectroscopy configurations, the separate acquisition of background and sample measurements have significant impact on data quality due to the need to perform subsequent measurements as well as the change in beam coupling geometry due to the removal of the sample in the reference measurement. In this short paper, we report on the design and build of a dual-polarization TDS system to perform synchronous background/sample measurements. This is achieved through the splitting of the PCA-generated THz beam with a THz polarizer to obtain two orthogonal polarized beams which are balanced and modulate the indices of two separate crystals on which the probe beam (also split) is reflected off before being detected. The two branches of the system show good similarity, and can be used to perform background and sample measurements synchronously, thus not being affected by changes in temperature and humidity, as well as small fluctuations in source power. Small differences in detector optical efficiency can be calibrated out at the start of a measurement session.