Speaker
Description
Terahertz time-domain spectroscopy (THz-TDS) is a non-invasive technique capable of probing the complex dielectric properties of a wide range of organic and inorganic materials. When combined with an ultrafast pump pulse, THz-TDS systems enable the investigation of nonequilibrium excitations in semiconductors, superconductors, topological insulators, Dirac and Weyl semimetals, heavy-fermion systems, and quantum spin liquids.
Although significant progress has been made in extending the bandwidth of the THz-TDS over the past decades, systems capable of efficiently covering the frequency range between 5 and 15 THz remain scarce. Conventional THz generation and detection schemes based on difference-frequency mixing in second-order nonlinear semiconductor crystals are fundamentally limited in this range by strong phonon absorption. Alternative approaches, such as air-plasma and metallic spintronic THz sources, can access the 5-15 THz region but typically suffer from a relatively low generation efficiency.
Emerging organic nonlinear crystals offer new opportunities for efficient THz generation and detection from near-infrared pulses due to their large optical nonlinear coefficients and favorable phase-matching conditions. We present an ultrabroadband THz-TDS system that uses organic BNA crystals for both THz generation via optical rectification and detection via conventional electro-optic sampling, combined with a tunable single-ring hollow-core photonic crystal fiber (HC-PCF) compressor to temporally shorten the near-infrared pulses from a commercial Yb:KGW ultrafast amplifier at 1030 nm. The resulting system spans 0.3 to 25.2 THz, with a significant portion of the spectrum falling within the “new THz gap” between 5 and 15 THz.
This configuration extends the accessible spectral range beyond that previously achieved with Yb-based organic-crystal systems and offers a streamlined single-color, broadband THz-TDS platform. The presented system provides a robust tool for exploring phonon and polariton dynamics in two-dimensional and semiconductor systems, as well as excitonic phenomena in quantum materials.
| Keyword-1 | Broadband THz spectroscopy |
|---|---|
| Keyword-2 | New THz gap (5–15 THz) |
| Keyword-3 | Organic crystal |