Terahertz Physics

Terahertz physics explores electromagnetic radiation in the 0.1–10 THz frequency range, bridging the gap between electronics and photonics. In this band, photon energies correspond to millielectronvolts, enabling unique access to molecular rotations, lattice vibrations and low‐energy electronic excitations. Advances in ultrafast optics have yielded time‐domain spectroscopy systems that generate and detect single‐cycle pulses under one picosecond in duration, while continuous‐wave techniques offer high spectral resolution. The strong interaction of terahertz fields with charge carriers supports studies of semiconductor transport, superconducting dynamics and carrier–phonon coupling. Nonlinear phenomena such as saturable absorption, harmonic generation and impact ionisation become prominent at high field strengths, driving interest in compact sources and modulators. Metamaterials and metasurfaces engineered at subwavelength scales provide tailored amplitude, phase and polarisation control, with reconfigurable elements based on graphene, phase‐change media and organics. Applications span high‐speed wireless communication, non‐invasive imaging, security screening, chemical sensing and biomedical diagnostics. Ongoing efforts focus on enhancing source power, detector sensitivity and integration on chip, with an eye to mass‐manufacturable terahertz circuits and systems.

Research from Nature Portfolio

In magnetoelectric insulators, optical excitation has been used to launch coherent spin‐wave modes (electromagnons) at terahertz frequencies. Studies of antiferromagnetic thin films have revealed two distinct excitation pathways—off‐resonant spin torques in certain crystallographic orientations and strain‐wave‐induced torques following ultrafast metal heating—each emitting narrowband or broadband terahertz pulses via the inverse spin Hall effect. Detailed mapping of these processes down to timescales below 50 fs has opened routes to opto‐spintronic control at terahertz rates. Complementing this, terahertz emission spectroscopy has been harnessed as a contact‐free magnetometer, capable of resolving sub‐picosecond magnetisation dynamics in encapsulated materials under ambient conditions. By analysing emitted waveforms, researchers have disentangled incoherent magnon‐quenching from coherent lattice‐driven exchange modulation, providing calibrated, ultrafast access to magnetic order. Furthermore, careful interface and defect engineering in spintronic heterostructures has enabled tuning of the scattering lifetime of photoexcited electrons, thereby shaping the emitted terahertz spectrum. These advances define a materials‐based roadmap for optimising ultrabroadband, high‐efficiency terahertz spintronic emitters.

Research from all publishers

Research on two‐dimensional semiconductors has demonstrated coherent terahertz emission from monolayer and multilayer molybdenum disulfide under two‐colour optical excitation. By adjusting the relative phase and polarisation between fundamental and second‐harmonic pulses, the amplitude and waveform of emitted terahertz radiation can be precisely controlled, illustrating quantum‐interference‐driven photocurrents in indirect‐gap materials. In the realm of nonlinear generation, a universal modelling framework has been developed for optical rectification in nanoscale dielectric materials. This approach disentangles phonon‐polaritonic and electronic contributions across a broad spectral window, yielding effective second‐order susceptibility tensors that guide the design of metasurfaces for efficient terahertz generation at multiple frequencies. Meanwhile, fully dielectric semiconductor metasurfaces exploiting morphology‐mediated resonances have achieved over fortyfold enhancement in terahertz pulse emission compared with unpatterned films. By harnessing intrinsic quadratic nonlinearity and high‐Q resonances, these scalable emitters pave the way for large‐area, patternable terahertz sources without metallic losses.

Terahertz Physics publication trend

The graph below shows the total number of articles in terahertz physics across all publications each year (not limited to Nature Index journals).

Technical terms

Terahertz radiation: Electromagnetic waves in the 0.1–10 THz range, corresponding to energies of a few millielectronvolts.

Time‐domain spectroscopy (TDS): Technique that records the electric‐field waveform of single‐cycle terahertz pulses versus time for broadband spectral analysis.

Inverse spin Hall effect: Conversion of a spin current into a transverse charge current in materials with strong spin–orbit coupling, enabling terahertz emission.

Electromagnon: Hybrid excitation in multiferroics arising from coupling between electric fields and spin waves, active at terahertz frequencies.

Optical rectification: Second‐order nonlinear process in which an intense optical pulse induces a transient polarization that radiates terahertz fields.

Metasurface: Planar array of engineered resonators at subwavelength scales that tailor amplitude, phase or polarisation of terahertz waves.

References

1. Coherent Terahertz Wave Generation from Mono- and Multilayer MoS 2 through Quantum Interference. Ultrafast Science (2024).
2. THz Generation via Optical Rectification in Nanomaterials: Universal Modeling Approach and Effective χ¯¯(2)$\bar{\bar{\chi }}^{(2)}$ Description. Laser & Photonics Review (2023).
3. Resonant Fully Dielectric Metasurfaces for Ultrafast Terahertz Pulse Generation. Advanced Optical Materials (2024).
4. Emission of coherent THz magnons in an antiferromagnetic insulator triggered by ultrafast spin–phonon interactions. Nature Communications (2023).
5. Ultrafast terahertz magnetometry. Nature Communications (2020).
6. Modification of spintronic terahertz emitter performance through defect engineering. Scientific Reports (2019).
7. The 2017 terahertz science and technology roadmap. Journal of Physics D (2017).
8. Terahertz nonlinear conduction and absorption saturation in silicon waveguides. Optica (2015).
9. Impact ionization in high resistivity silicon induced by an intense terahertz field enhanced by an antenna array. New Journal of Physics (2015).
10. Widely Tunable Terahertz Phase Modulation with Gate-Controlled Graphene Metasurfaces. Physical Review X (2015).
11. Vanadium dioxide based frequency tunable metasurface filters for realizing reconfigurable terahertz optical phase and polarization control.. Optics Express (2018).
12. Tuning direct-written terahertz metadevices with organic mixed ion-electron conductors. Nature Communications (2024).
13. Optoelectronic frequency-modulated continuous-wave terahertz spectroscopy with 4 THz bandwidth. Nature Communications (2021).