Two-dimensional (2D) nanomaterials, such as graphene and transition metal dichalcogenides (TMDs), offer remarkable opportunities for shaping the future of nanoscale optoelectronics and photonics. Their atomically thin structure, exceptional carrier mobility, and strong light–matter coupling make them promising candidates for the development of nanodevices operating at terahertz (THz) frequencies — a spectral region critical for next-generation information processing technologies. Among their most compelling features is their potential to exhibit strong and highly tunable nonlinear optical responses under intense THz excitation, a property that could enable key functionalities such as frequency conversion, field-driven switching, and ultrafast modulation at unprecedented speed and spatial resolution. The TeraNanoLIGHT project was established to explore these nonlinear phenomena at the intersection of ultrafast optics and nanoscience. The central aim was to investigate the interaction between intense, few-cycle THz fields and quantum-confined 2D materials with nanometer spatial and femtosecond temporal resolution. This regime — where both strong-field effects and quantum confinement dominate — remains largely unexplored, yet holds the potential to reveal new light–matter interaction mechanisms that are inaccessible in either far-field or weak-field conditions. To reach the necessary field strengths, the project employed scattering-type scanning near-field optical microscopy (s-SNOM) to confine THz pulses to nanoscale hotspots, achieving local electric fields exceeding several megavolts per centimeter. Within this framework, TeraNanoLIGHT set out to study THz-induced nonlinearities in several contexts. One key objective was to observe and characterize the propagation of THz surface plasmons in graphene as a function of field strength, moving from linear to nonlinear dynamics. Another goal was to investigate how oscillating THz fields act as ultrafast AC biases, enabling non-resonant nonlinearities such as intervalley scattering or lightwave-driven transport. The project also aimed to explore the conditions for generating high-order harmonics in atomically thin materials, especially TMD monolayers and heterostructures with tailored interlayer symmetries. Finally, TeraNanoLIGHT considered whether these intense, localized interactions could themselves be used to improve the spatial resolution of near-field microscopy. By achieving these objectives, the project aimed to contribute to a deeper understanding of ultrafast, nonlinear THz interactions in low-dimensional systems.
