RESUMO
Terahertz (THz) radiation will play a pivotal role in wireless communications, sensing, spectroscopy and imaging technologies in the decades to come. THz emitters and receivers should thus be simplified in their design and miniaturized to become a commodity. In this work we demonstrate scalable photoconductive THz receivers based on horizontally-grown InAs nanowires (NWs) embedded in a bow-tie antenna that work at room temperature. The NWs provide a short photoconductivity lifetime while conserving high electron mobility. The large surface-to-volume ratio also ensures low dark current and thus low thermal noise, compared to narrow-bandgap bulk devices. By engineering the NW morphology, the NWs exhibit greatly different photoconductivity lifetimes, enabling the receivers to detect THz photons via both direct and integrating sampling modes. The broadband NW receivers are compatible with gating lasers across the entire range of telecom wavelengths (1.2-1.6 µm) and thus are ideal for inexpensive all-optical fibre-based THz time-domain spectroscopy and imaging systems. The devices are deterministically positioned by lithography and thus scalable to the wafer scale, opening the path for a new generation of commercial THz receivers.
RESUMO
It has been shown that graphene exhibits unique electronic, thermal, mechanical, and optical properties. In particular, due to its gapless band structure and linear dispersion relation around the Dirac points, graphene exhibits a strong nonlinear optical response, which has been theoretically predicted to depend on the number of graphene layers. In this Letter, we experimentally validate the theoretical predictions by probing multilayer graphene χ(3) nonlinearities. The intensity of the four-wave mixing signal is observed to grow monotonically as a function of the number of graphene layers, up to a maximum intensity corresponding to â¼32 layers, after which it decreases, well in agreement with theoretical predictions.
