Towards single-pulse terahertz spectroscopy at MHz rates

We perform single-pulse time-resolved THz detection at repetition rates up to 1.1 MHz with a table-top system. Our detection scheme combines electro-optic sampling of THz pulses with spectral encoding onto a chirped near-infrared pulse, followed by time-stretch spectroscopy to monitor the oscillating electric field of each THz pulse. We demonstrate the concept by monitoring cumulative carrier injection dynamics in silicon at 50 kHz until a saturation density is reached and investigate signal-to-noise ratio at different repetition rates. This technique paves the way towards fundamental research on fast and non-reproducible phenomena requiring real-time monitoring as well as industrial applications requiring fast data acquisition for non-invasive quality control.