Abstract-One- and two-dimensional photo-imprinted diffraction gratings for manipulating terahertz waves

Ioannis Chatzakis^1,a), Philippe Tassin^1,b), Liang Luo¹, Nian-Hai Shen¹, Lei Zhang¹, Jigang Wang^1,c), Thomas Koschny¹ and C. M. Soukoulis^1,2,d)
http://scitation.aip.org/content/aip/journal/apl/103/4/10.1063/1.4813620
a) Present address: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
b) Author to whom correspondence should be addressed: Electronic mail: tassin@ameslab.gov
c) Electronic mail: jgwang@iastate.edu, jwang@ameslab.gov
d) Electronic mail: soukoulis@ameslab.gov
Appl. Phys. Lett. 103, 043101 (2013); http://dx.doi.org/10.1063/1.4813620

Emerging technology based on artificial materials containing metallic structures has raised the prospect for unprecedented control of terahertz waves. The functionality of these devices is static by the very nature of their metallic composition, although some degree of tunability can be achieved by incorporating electrically biased semiconductors. Here, we demonstrate a photonic structure by projecting the optical image of a metal mask onto a thin GaAs substrate using a femtosecond pulsed laser source. We show that the resulting high-contrast pattern of photo-excited carriers can create diffractive elements operating in transmission, potentially providing a route to terahertz components with reconfigurable functionality.

Abstract-Reversible modulation and ultrafast dynamics of terahertz resonances in strongly photoexcited metamaterials

http://prb.aps.org/abstract/PRB/v86/i12/e125110

I. Chatzakis¹, L. Luo¹, J. Wang^1,*, N.-H. Shen^1,†, T. Koschny¹, J. Zhou^2,‡, and C. M. Soukoulis^1,3
1Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
²Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
³Institute of Electronic Structure and Laser, FORTH, 71110 Heraklion, Crete, Greece

Received 24 December 2011; revised 30 July 2012; published 7 September 2012

We demonstrate an ultrafast reversible modulation of resonant terahertz (THz) response in strongly photoexcited metamaterials. The transient spectral-temporal response of the dipole transition ∼1.6 THz exhibits a distinct nonmonotonic variation as a function of pump fluence. The transition energy shift, strength, spectral width, and density-dependent ultrafast relaxation manifest a remarkable reemergence of the transmission dip after initial quenching. Our simulations, incorporating the first-order diffraction from the photoinduced transient grating, reproduce the salient features, providing a new avenue for designing nonlinear and frequency-agile THz modulators.

©2012 American Physical Society

URL:

http://link.aps.org/doi/10.1103/PhysRevB.86.125110

DOI:

10.1103/PhysRevB.86.125110

PACS:

78.67.Pt, 42.25.Bs, 78.20.-e, 78.47.-p

Two-dimensional polaritonic photonic crystals as terahertz uniaxial metamaterials

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MY NOTE: THIS ABSTRACT IS INCLUDED HERE, BECAUSE IT DESCRIBES THE WORK TO A SUFFICIENT DEGREE THAT WILL BE OF INTEREST TO SOME IN THE LAY COMMUNITY REGARDING THE USE OF METAMATERIALS IN THz.

http://prb.aps.org/abstract/PRB/v84/i3/e035128

Emerging technologies such as quantum cascade lasers enabled the investigation of the most interesting, yet very little explored, THz part of the electromagnetic (EM) spectrum. These THz sources impose a dire need for novel materials suitable for optical components at such frequencies, as traditional visible optics is not appropriate for THz. Here, we explore two-dimensional (2D) photonic crystals (PCs) with either or both constituents made of polar materials, having a polariton gap within or close to the THz regime. Our objective is to create polaritonic composites that behave as extraordinary effective homogeneous uniaxial media, with flexibly engineered EM wave dispersion and high transmissivity in the THz frequency region. Accordingly, it is most important to be able to identify when 2D composites act as effective bulk uniaxial media. Clearly, deviation from standard effective medium predictions does not necessarily imply bulk effective medium picture breakdown. We developed a reliable criterion which provides a clear angular signature of effective medium behavior in 2D composites, even in the presence of high losses. Relying on this criterion, we characterized polar-dielectric and polar-polar PC composites acting as homogeneous uniaxial metamaterials for any arbitrary incident angle. We selected certain cases of effective metamaterial composites which demonstrate a polarization filter behavior. In particular, our results suggest that an unpolarized source will lead to either an S- or a P-polarized wave just by changing the angle of incidence of the impinging wave, irrespective of the thickness of the composite metamaterial. Furthermore, we show that transmission through a LiF/NaCl composite can be as high as 20%, even though transmission through an identical slab made from either of the two polar constituents would be next to zero. We analyze and discuss the physical origins underpinning such extraordinary angular transmission profile of these metamaterial composites. Our results suggest that appropriate mixing of polar materials with each other or with high-index dielectrics provides a route to making advanced photonic materials that are highly attractive for THz optical components.

©2011 American Physical Society

URL:

http://link.aps.org/doi/10.1103/PhysRevB.84.035128

DOI:

10.1103/PhysRevB.84.035128

PACS:

81.05.Xj, 78.20.Ci, 41.20.Jb, 42.70.Qs