Collective antenna effects in the terahertz and infrared response of highly aligned carbon nanotube arrays

Abstract

We study macroscopically-aligned single-wall carbon nanotube arrays with uniform lengths via polarization-dependent terahertz and infrared transmission spectroscopy. Polarization anisotropy is extreme at frequencies less than ∼3 THz with no sign of attenuation when the polarization is perpendicular to the alignment direction. The attenuation for both parallel and perpendicular polarizations increases with increasing frequency, exhibiting a pronounced and broad peak around 10 THz in the parallel case. We model the electromagnetic response of the sample by taking into account both radiative scattering and absorption losses. We show that our sample acts as an effective antenna due to the high degree of alignment, exhibiting much larger radiative scattering than absorption in the mid/far-infrared range. Our calculated attenuation spectrum clearly shows a non-Drude peak at ∼10 THz in agreement with the experiment.

Plasmonic Nature of the Terahertz Conductivity Peak in Single-Wall Carbon Nanotubes

“…Also, strong polarization dependence has been universally confirmed by many authors, with no resonance expected for polarization perpendicular to the nanotube axis. 16,19,26 To gain more quantitative understanding via comparison with theoretical models, we performed KramersKronig (KK) transformation on our broadband transmission spectra T (ω) and obtained the phase spectra φ t (ω). 20,24,43 We first interpolated the T (ω) data in the region between the THz and IR and then applied fourpass binomial smoothing to prevent spikes.…”

“…[13][14][15][16][17][18][19][20][21][22][23][24][25][26] Two interpretations have emerged regarding the THz peak, but there is no consensus about its origin. One of the possible mechanisms proposed by many authors 14,[20][21][22] is based on interband absorption across the curvature-induced bandgap 27,28 in non-armchair metallic SWCNTs, while the other is the plasmon resonance in metallic and doped semiconducting SWCNTs due to their finite lengths.…”

Dicke superradiance in solids [Invited]

“…Although Dicke's theory was purely quantum mechanical, some aspects of SR are classical in essence. Particularly, the aspect of synchronization and self-organization among oscillating dipoles, intrinsic in all SR processes, has many classical analogues, such as coupled pendulums [40], metronomes [41], clapping hands [42], coupled plasmonic waveguides [43], and an array of carbon nanotube antennas [44]. It is a natural consequence of electromagnetism that N synchronized dipole oscillators, or antennas, radiate N 2 times more strongly.…”

Soliton nanoantennas in two-dimensional arrays of quantum dots

“…The respective lens-shaped In 0.65 Al 0. 35 As quantum dot is a part of a sphere with a fixed height of 3.4 nm and base diameter of 38 nm. The photoluminescence spectrum of the QD array is time-resolved at the excitation density of 1065 W/cm 2 , at 77 K. The corresponding exciton lifetime, found from the measurements, is 800 − 1200 ps, which complies with the respective value for the arrays of the first type [52].…”

“…In particular, it stimulates bridging the realms of macroscopic antennas and nanoantennas, using new materials with specific electronic properties. In this context, it is relevant to mention carbon nanotubes and nanotube arrays [32]- [35], plasmonic noblemetal wires [36,37], graphene nanoribbons [38], semiconductor QDs [39,41], etc. These types of nano-antennas have been offered as promising elements for industrial design and commercial manufacturing.…”