Terahertz Detection Based on Spectral-Domain Interferometry Using Mach-Zehnder Interferometer

We demonstrate the use of a Mach-Zehnder interferometer (MZI) to improve the performance of terahertz electric field measurements based on spectral-domain interferometry. The interferometer is introduced into the probe beam line to improve the temporal overlap between the two probe pulses. The probe pulse in the sample arm of the interferometer passes through the detection crystal and overlaps with the terahertz pulse, while the probe pulse in the reference arm does not. We measure the phase change between spectral components of these two pulses using spectral-domain interferometry. Using this new technique, we enable an unlimited temporal scanning window without the loss in the signal-to-noise ratio, thus overcoming the major limitation of conventional spectral-domain interferometry techniques for terahertz electric field detection.