Zeptojoule detection of terahertz pulses by parametric frequency upconversion.

We combine parametric frequency upconversion with the single-photon counting technology to achieve terahertz (THz) detection sensitivity down to the zeptojoule (zJ) pulse energy level. Our detection scheme employs a near-infrared ultrafast source, a GaP nonlinear crystal, optical filters, and a single-photon avalanche diode. This configuration is able to resolve 1.

Compact, low-cost, and broadband terahertz time-domain spectrometer.

Terahertz time-domain spectroscopy (THz-TDS) is a powerful technique that enables the characterization of a large range of bulk materials, devices, and products. Although this technique has been increasingly used in research and industry, the standard THz-TDS configuration relying on the use of a near-infrared (NIR) laser source remains experimentally complex and relatively costly, impeding its availability to those without the expertise to build a high-performance setup based on nonlinear optics or without the financial means to acquire a commercial unit. Broadband THz-TDS systems require an even larger financial investment, primarily because the generation and detection of spectral components exceeding 3 THz typically need an ultrafast NIR source delivering sub-100-fs pulses.

Single-pulse terahertz spectroscopy monitoring sub-millisecond time dynamics at a rate of 50 kHz.

Slow motion movies allow us to see intricate details of the mechanical dynamics of complex phenomena. If the images in each frame are replaced by terahertz (THz) waves, such movies can monitor low-energy resonances and reveal fast structural or chemical transitions. Here, we combine THz spectroscopy as a non-invasive optical probe with a real-time monitoring technique to demonstrate the ability to resolve non-reproducible phenomena at 50k frames per second, extracting each of the generated THz waveforms every 20 μs.