Generation of Terahertz Radiation by Optical Excitation of Aligned Carbon Nanotubes

Abstract

We have generated coherent pulses of terahertz radiation from macroscopic arrays of aligned single-wall carbon nanotubes (SWCNTs) excited by femtosecond optical pulses without externally applied bias. The generated terahertz radiation is polarized along the SWCNT alignment direction. We propose that top-bottom asymmetry in the SWCNT arrays produces a built-in electric field in semiconducting SWCNTs, which enables generation of polarized terahertz radiation by a transient photocurrent surge directed along the nanotube axis.

One-dimensional carbon nanostructures for terahertz electron-beam radiation

“…In the area of terahertz sources, several theoretical proposals involving graphene [27][28][29][30][31][32][33] or carbon nanotubes [34][35][36][37][38][39] have been presented, based on several mechanisms including interband electronic transitions, tunable plasmonic excitations, or real-space charge oscillations. The experimental demonstrations of terahertz amplification and emission in optically pumped samples have also already been reported [40][41][42][43][44].…”

“…II A are produced by epitaxial growth techniques [9], which are readily applicable to the fabrication of ordered arrays with macroscale (e.g., millimeter-range) dimensions. Significant progress has also been reported in recent years towards the synthesis of high-density arrays of aligned nanotubes [44,62]. In principle, these ZZ-GNR or AC-SWNT arrays could also be combined with an optical cavity for the demonstration of coherent stimulated emission, and ultimately even lasing, in analogy with the operation of traditional FELs.…”

Plasmonic Terahertz Amplification in Graphene-Based Asymmetric Hyperbolic Metamaterial

“…Nowadays, carbon-based nanomaterials are considered as attractive candidates for the development of next generation photonic devices. Generation of terahertz (THz) radiation by optically excited aligned carbon nanotubes, and single layer graphene was reported in [1][2][3]. These mainly experimental works demonstrate a practical possibility to obtain THz emission from carbon nanostructures.…”

“…Since k z is complex for gain or loss medium, providing the frequency ω is real, the isofrequencies at the planes k x /k 0 , Re(k z )/k 0 and k x /k 0 , Im(k z )/k 0 are shown separately, demonstrating hyperbolic dispersion (Figure 4a z )/k 0 is very large and negative that demonstrates a gain in AHMM. The value of k (1) z is small, approximately the same as in host medium, since it corresponds to the wave whose electric field vector is orthogonal to graphene sheets and does not interact with the graphene plasmonic system. Note that this resonance is not a size resonance since the size does not enter Equation (6) and the resonant frequency depends only on such a geometrical parameter as the tilt angle φ.…”

Strong Light–Matter Coupling in Carbon Nanotubes as a Route to Exciton Brightening

“…27 Furthermore, the single chirality tubes have been assembled into well-aligned films via controlled vacuum filtration. [28][29][30] These achievements give confidence that the problems of SWCNT sample fabrication will be gradually solved with improvements in experimental techniques.…”