Nanoconcentration of Terahertz Radiation in Plasmonic Waveguides

TL;DR

This paper explores the fundamental limits and optimal designs for nanoconcentrating terahertz radiation in plasmonic waveguides, enabling enhanced THz imaging, spectroscopy, and nonlinear effects at nanoscale resolutions.

Contribution

It establishes the theoretical limits and optimal shapes for nanoconcentrating THz radiation in metal/dielectric waveguides, predicting significant intensity enhancement at nanoscale dimensions.

Findings

Achievable nanoconcentration of THz radiation with 10-250x intensity increase.

Final spot size of 100-250 nm for THz radiation.

Enhanced spatial resolution and nonlinear THz effects observation.

Abstract

Recent years have seen an explosive research and development of nanoplasmonics in the visible and near-infrared (near-ir) frequency regions. One of the most fundamental effects in nanoplasmonics is nano-concentration of optical energy. Plasmonic nanofocusing has been predicted and experimentally achieved. It will be very beneficial for the fundamental science, engineering, environmental, and defense applications to be able to nano-concentrate terahertz radiation (frequency 1 - 10 THz or vacuum wavelength 300 - 30 microns). This will allow for the nanoscale spatial resolution for THz imaging and introduce the THz spectroscopy on the nanoscale, taking full advantage of the rich THz spectra and submicron to nanoscale structures of many engineering, physical, and biological objects of wide interest: electronic components (integrated circuits, etc.), bacteria, their spores, viruses, macromolecules, carbon clusters and nanotubes, etc. In this Letter we establish the principal limits for the nanoconcentration of the THz radiation in metal/dielectric waveguides and determine their optimum shapes required for this nanoconcentration We predict that the adiabatic compression of THz radiation from the initial spot size of light wavelength to the final size of R = 100 - 250 nm can be achieved with the THz radiation intensity increased by a factor of 10 to 250. This THz energy nanoconcentration will not only improve the spatial resolution and increase the signal/noise ratio for the THz imaging and spectroscopy, but in combination with the recently developed sources of powerful THz pulses will allow the observation of nonlinear THz effects and a carrying out a variety of nonlinear spectroscopies (such as two-dimensional spectroscopy), which are highly informative.