Highly absorbing nano-scale metal films for terahertz applications

Alves, Fabio; Karamitros, Apostolos; Grbovic, Dragoslav; Kearney, Brian; Karunasiri, Gamani

doi:10.1117/1.oe.51.6.063801

Cited by 28 publications

(18 citation statements)

References 9 publications

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“…Ti was modeled as having a sheet resistance of 220 Ω/sq based on four-point probe measurements. The exact thickness of the Ti is irrelevant as long as the sheet resistance is well known [20] and was estimated as 10 nm from previous depositions. As in [15], the overetching of SiO x is included in the models, producing a slight blue shift in the resonant absorption frequency due to an effectively smaller index of refraction.…”

Section: Discussionmentioning

confidence: 99%

Terahertz metamaterial absorbers with an embedded resistive layer

Kearney¹,

Alves²,

Grbovic³

et al. 2013

Opt. Mater. Express

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A conductive layer of Ti, with a sheet resistance of about 220 Ω/sq, was placed in the dielectric spacer of an Al/SiO x /Al metamaterial terahertz absorber at various depths to probe the effect on the absorption of terahertz radiation. For a square size of 15 µm and a periodicity of 21 µm, and dielectric thickness approximately 1.6 µm, maximum absorption was 60%, 88%, and 94% for Ti layers 297, 765, and 1270 nm deep into the SiO x . Finite element simulations of the absorption correlated well with that of the measurements. This indicates that metamaterials with an embedded high temperature coefficient of resistance (TCR) conducting layer can be used for fabrication of microbolometers with tuned spectral sensitivity.

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Section: Discussionmentioning

confidence: 99%

Terahertz metamaterial absorbers with an embedded resistive layer

Kearney¹,

Alves²,

Grbovic³

et al. 2013

Opt. Mater. Express

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“…As a continuation of previous work, 18,19 the absorber used in our model was designed as a thin metallic layer located on a glass substrate (SiO 2 ). Through the usage of such a metalglass configuration, the transmission of a metal film is the same, regardless of the direction in which it is measured (either the metal or the glass side).…”

Section: Thz Absorber Setupmentioning

confidence: 99%

“…[15][16][17] Originally developed for infrared wavelengths, the microbolometer detectors were used for imaging in the THz spectral range using illumination from a quantum cascade laser. [17][18][19] Moreover, for normal incidence, it has been shown that a free-standing metallic layer can absorb up to 50% of the incident radiation. It has been shown that thin metal films deposited on dielectrics provide good THz absorption due to resistive losses in the film.…”

Section: Introductionmentioning

confidence: 99%

Optimizing detection methods for terahertz bioimaging applications

et al. 2015

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We propose a new approach for efficient detection of terahertz (THz) radiation in biomedical imaging applications. A double-layered absorber consisting of a 32-nm-thick aluminum (Al) metallic layer, located on a glass medium (SiO 2 ) of 1 mm thickness, was fabricated and used to design a fine-tuned absorber through a theoretical and finite element modeling process. The results indicate that the proposed low-cost, double-layered absorber can be tuned based on the metal layer sheet resistance and the thickness of various glass media. This can be done in a way that takes advantage of the diversity of the absorption of the metal films in the desired THz domain (6 to 10 THz). It was found that the composite absorber could absorb up to 86% (a percentage exceeding the 50%, previously shown to be the highest achievable when using single thin metal layer) and reflect <1% of the incident THz power. This approach will enable monitoring of the transmission coefficient (THz transmission fingerprint) of the biosample with high accuracy, while also making the proposed double-layered absorber a good candidate for a microbolometer pixel's active element. Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/19/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Optical Engineering 067107-2 June 2015 • Vol. 54(6) Bolakis et al.: Optimizing detection methods for terahertz bioimaging applications Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/19/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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“…When broadband detection is desired, metallic ultra-thin films (<10 nm) can be used 1, 2 , however when resonant detection can be used, typically when external illumination by a THz laser is used, metamaterial absorbers become a suitable option 3,4 . Both approaches have been demonstrated by our research group [1][2][3][4] , and designing such structures requires great effort on modeling and simulation to optimize the desired optical characteristics of the films. In our previous work the Rouard Method (RM) 1 and finite element (FE) simulation were used 2 .…”

Section: Introductionmentioning

confidence: 97%

Modeling and simulation of multilayered thin films for terahertz detection

Martin

Alves

Santos

et al. 2014

Micro- And Nanotechnology Sensors, Systems, and Applications VI

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In this article we demonstrate a method based on Transfer Matrix (TMM) that can be used to analyze optical properties of multilayered thin films and planar metamaterials for terahertz (THz) detection. Producing and testing such films require host substrates that can be up to 4 orders of magnitude thicker than the THz-sensitive films. Therefore, the ability to efficiently model, simulate and accurately predict the optical properties of multilayered structures, with significant differences in thickness, is crucial to designing sensors with maximized absorption. This method, which provides an analytical tool, less computationally intensive then finite element modeling, can be used for films composed of any number of layers with arbitrary thicknesses, aspect ratios and arbitrary angles of incidence. Homogeneous or patterned (metamaterials) films can be modeled enabling accurate analysis of positive and negative index materials indistinctly. Reflection, transmission and absorption of metallic/dielectric nanolaminates, metallic thin films and planar metamaterial films are analyzed and compared with experimental measurements and FE simulations. Results show good agreement for a wide range of structures, materials and frequencies and indicate that the method has a great potential for design and optimization of sophisticated multilayered structures for THz detection and beyond.

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Highly absorbing nano-scale metal films for terahertz applications

Cited by 28 publications

References 9 publications

Terahertz metamaterial absorbers with an embedded resistive layer

Terahertz metamaterial absorbers with an embedded resistive layer

Optimizing detection methods for terahertz bioimaging applications

Modeling and simulation of multilayered thin films for terahertz detection

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