The 2023 terahertz science and technology roadmap

Abstract

Terahertz (THz) radiation encompasses a wide spectral range within the electromagnetic spectrum that extends from microwaves to the far infrared (100 GHz to ~30 THz). Within its frequency boundaries exist a broad variety of scientific disciplines that have presented, and continue to present, technical challenges to researchers. During the past 50 years, for instance, the demands of the scientific community have substantially evolved and with a need for advanced instrumentation to support radio astronomy, Earth observation, weather forecasting, security imaging, telecommunications, non-destructive device testing and much more. Furthermore, applications have required an emergence of technology from the laboratory environment to production-scale supply and in-the-field deployments ranging from harsh ground-based locations to deep space. In addressing these requirements, the research and development community has advanced related technology and bridged the transition between electronics and photonics that high frequency operation demands. The multidisciplinary nature of THz work was our stimulus for creating the 2017 THz Science and Technology Roadmap (S S Dhillon et al 2017 J. Phys. D: Appl. Phys. 50 043001). As one might envisage, though, there remains much to explore both scientifically and technically and the field has continued to develop and expand rapidly. It is timely, therefore, to revise our previous roadmap and in this 2023 version we both provide an update on key developments in established technical areas that have important scientific and public benefit, and highlight new and emerging areas that show particular promise. The developments that we describe thus span from fundamental scientific research, such as THz astronomy and the emergent area of THz quantum optics, to highly applied and commercially and societally impactful subjects that include 6G THz communications, medical imaging, and climate monitoring and prediction.

Phonon Polaritonics in Broad Terahertz Frequency Range with Quantum Paraelectric SrTiO3

“…[87] Both SrTiO 3 and SU-8 are centrosymmetric materials, and thus do not have intrinsic second harmonic generation. The THz electric field inside the materials induces an effective second-order nonlinearity according to 𝜒 (2) = E THz 𝜒 (3) , which is probed by a far-field pulse with the center wavelength of 800 nm. The spot size of the probe pulse covers the entire central disk but is still sub-wavelength with respect to the THz field.…”

“…Recent development of terahertz (THz) spectroscopy and imaging have led to new fundamental scientific discoveries and applications in materials physics and biochemistry. [1,2] For example, at wavelengths below 15 μm. [26,[42][43][44][45][46][47][48][49] Some III-V semiconductors show promise for expanding infrared photonics like emitters, waveguides, and resonators toward longer wavelengths but with very limited bandwidth due to the narrow PhP resonance of the materials.…”

Non-Linear Conductivity Response of Graphene on Thin-Film PET Characterized by Transmission and Reflection Air-Plasma THz-TDS

“…The air-plasma-based THz-TDS setup is shown in Figure 1 . To obtain high THz field strengths, laser pulses centered at a wavelength of 1.4 µm and 40 fs duration from a high-energy optical parametric amplifier (HE-TOPAS) pumped by a Ti: sapphire amplifier laser system (SpectraPhysics Spitfire Ace, 0.8 µm wavelength, 6 mJ pulse energy, 35 fs pulse duration, 1 kHz repetition rate) was used as the driving laser source [ 21 ]. A 100 µm thick BBO crystal was inserted for inline second harmonic (SH) generation after a lens with a 300 mm focal length.…”

Nonlinear Conductivity Response of Graphene on Thin-Film PET Characterized by Transmission and Reflection Air-Plasma THz-TDS

“…1. To obtain high THz field strengths, laser pulses centered at a wavelength of 1.4 µm and 40-fs duration from a highenergy optical parametric amplifier (HE-TOPAS) pumped by a Ti:sapphire amplidied laser system (SpectraPhysics Spitfire Ace, 0.8 µm wavelength, 6 mJ pulse energy, 35 fs pulse duration, 1 kHz repetition rate) was used as the driving laser source [21]. A 100-µm-thick BBO crystal was inserted for inline second harmonic (SH) generation after a lens with a 300-mm focal length.…”