Abstract-Wavelength Scaling in Antenna-Enhanced Infrared Spectroscopy: Towards the Far-IR and THz Region

Ksenia Weber, Maxim L. Nesterov, Thomas Weiss, Michael Scherer, Mario Hentschel, Jochen Vogt, Christian Huck, Weiwu Li, Martin Dressel, Harald Giessen, and Frank Neubrech

ACS Photonics, Just Accepted Manuscript

DOI: 10.1021/acsphotonics.6b00534

Publication Date (Web): December 12, 2016

Copyright © 2016 American Chemical Society

http://pubsdc3.acs.org/doi/abs/10.1021/acsphotonics.6b00534

Weak vibrational signals in the infrared and terahertz spectral region can be enhanced by orders of magnitude when employing the electromagnetic near fields of plasmonic nanostructures. This approach is known as antenna-assisted surface-enhanced infrared absorption (SEIRA) and allows for a broad range of possible sensing applications. In the present work, we investigate the scaling of the SEIRA enhancement with wavelength, particularly towards the molecular fingerprint region (500 to 1500 cm-1). We apply the concept of SEIRA to perform resonant antenna-enhanced spectroscopy of molecules in a spectral range from 4.5 to 45 THz (6.6 to 67.5 µm wavelength, 148 to 1500 cm-1) using a standard Fourier transform infrared spectrometer. We fabricate arrays of rectangular gold antennas by electron-beam lithography and coat them with 30 nm thick layers of the fullerenes C60 and C70, respectively. For the single digit THz measurements, we utilize spin-coated amino acids, particularly threonine. The resonances of the structures are tailored to spectrally match the molecular absorption features. An increased SEIRA enhancement of two orders of magnitude is found for antennas resonant at 6.7 THz when compared to 45 THz, corresponding to a λ3 scaling over a frequency range of one order of magnitude. This scaling behavior is in excellent agreement with both numerical simulations and classical antenna theory. Further increase towards the single-digit THz region will yield the potential for ultrasensitive THz spectroscopy.

Abstract-Graphene: Sub-Terahertz Frequency-Domain Spectroscopy Reveals Single-Grain Mobility and Scatter Influence of Large-Area Graphene

• http://onlinelibrary.wiley.com/doi/10.1002/adma.201570111/abstract

On page 2635, L. Bogani and co-workers measure the electronic response of individual domains in wafer-sized chemical vapor deposition (CVD) graphene by means of contactless sub-THz interferometry. The intrinsic optical conductance of graphene is observed and the remarkable mobility is shown to be mainly limited by charged scatterers on the substrate. This sensitivity of sub-THz interferometry to contaminants can be used to easily quantify their presence and assess the quality of large graphene structures, which is essential for applications in touchscreens, as well as wearable and optoelectronic devices.

Abstract-Sub-Terahertz Frequency-Domain Spectroscopy Reveals Single-Grain Mobility and Scatter Influence of Large-Area Graphene

1. Christian Cervetti¹, 
2. Eric Heintze¹, 
3. Boris Gorshunov^1,2,3, 
4. Elena Zhukova^1,2,3,
5. Svyatoslav Lobanov^2,3, 
6. Alexander Hoyer⁴,
7. Marko Burghard⁴, 
8. Klaus Kern^4,5, 
9. Martin Dressel¹ and
10. Lapo Bogani^1,†,*

Article first published online: 18 MAR 2015

http://onlinelibrary.wiley.com/doi/10.1002/adma.201500599/abstract

DOI: 10.1002/adma.201500599

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The response of individual domains in wafer-sized chemical vapor deposition graphene is measured by contactless sub-terahertz interferometry, observing the intrinsic optical conductance and reaching very high mobility values. It is shown that charged scatterers limit the mobility, validating previous theoretical predictions, and sub-terahertz quality assessment is demonstrated, as necessary for large-scale applications in touchscreens and wearable and optoelectronic devices.

Abstract-Terahertz Conductivity of the Heavy-Fermion State in CeCoIn5

 Marc Scheffler, Thomas Weig, Martin Dressel, Hiroaki Shishido, Yuta Mizukami, Takahito Terashima, Takasada Shibauchi, Yuji Matsuda
http://arxiv.org/abs/1304.2325

The optical properties of thin films of the heavy-fermion compound CeCoIn5, which were deposited by molecular beam epitaxy onto MgF2 substrates, have been studied at frequencies 7 to 45 cm^{-1} (corresponding to 0.2 to 1.3 THz) and temperatures 2 to 300 K. We observe an electrodynamic behavior which is typical for heavy fermions, namely Drude-like conductivity with a relaxation rate at rather low frequencies. This relaxation rate increases almost linearly with temperature up to at least 30 K. The coherent heavy-fermion state, characterized by an increase of the effective mass, continuously evolves upon cooling and is not fully developed for temperatures as low as 5 K.