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On-chip interrogator based on Fourier transform spectroscopy

Grillo Peternella, F. (author), Esselink, Thomas (author), Dorsman, S.A. (author), Harmsma, Peter (author), Horsten, R.C. (author), Zuidwijk, T. (author), Urbach, Paul (author), Adam, A.J.L. (author)

In this paper, the design and the characterization of a novel interrogator based on integrated Fourier transform (FT) spectroscopy is presented. To the best of our knowledge, this is the first integrated FT spectrometer used for the interrogation of photonic sensors. It consists of a planar spatial heterodyne spectrometer, which is...

journal article 2019

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Investigation of Terahertz Emission from BiVO4 /Au Thin Film Interface

Kumar, N. (author), Abdi, F.F. (author), Trzesniewski, B. (author), Smith, W.A. (author), Planken, P.C.M. (author), Adam, A.J.L. (author)

We demonstrate emission of terahertz pulses from a BiVO4/Au thin film interface, illuminated with femtosecond laser pulses. Based on the experimental observations, we propose that the most likely cause of the THz emission is the Photo-Dember effect caused by the standing wave intensity distribution formed at the BiVO4/Au interfaces.

journal article 2015

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Optical characterization of gold-cuprous oxide interfaces for terahertz emission applications

Ramanandan, G.K.P. (author), Adam, A.J.L. (author), Ramakrishnan, G. (author), Petrik, P. (author), Hendrikx, R. (author), Planken, P.C.M. (author)

We show that the interface between gold and thermally formed cuprous oxide, which emits terahertz radiation when illuminated with ultrafast femtosecond lasers, is in fact an AuCu/Cu2O interface due to the formation of the thermal diffusion alloy AuCu. The alloy enables the formation of a Schottky-barrier-like electric field near the interface...

journal article 2014

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Nonexistence of pure S- and P-polarized surface waves at the interface between a perfect dielectric and a real metal

El Gawhary, O. (author), Adam, A.J.L. (author), Urbach, H.P. (author)

It is known that, at optical frequencies, a simple interface between a perfect dielectric and a real metal can sustain the propagation of surface plasmon polaritons only for P-polarized electromagnetic waves, being S-polarized surface plasmons are prohibited. In this work, we formally show that, strictly speaking, both polarization states are in...

journal article 2014

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Enhanced terahertz emission by coherent optical absorption in ultrathin semiconductor films on metals

Ramakrishnan, G. (author), Ramanandan, G.K.P. (author), Adam, A.J.L. (author), Xu, M. (author), Kumar, N. (author), Hendrikx, R.W.A. (author), Planken, P.C.M. (author)

We report on the surprisingly strong, broadband emission of coherent terahertz pulses from ultrathin layers of semiconductors such as amorphous silicon, germanium and polycrystalline cuprous oxide deposited on gold, upon illumination with femtosecond laser pulses. The strength of the emission is surprising because the materials are considered to...

journal article 2013

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Terahertz near-field spectroscopy of filled subwavelength sized apertures in thin metal films

Knab, J.R. (author), Adam, A.J.L. (author), Shaner, E. (author), Starmans, H.J.A.J. (author), Planken, P.C.M. (author)

We have measured terahertz near-field spectra of cesium iodide crystals as small as ?10 ?m in diameter, which were deposited on single, sub-wavelength-sized apertures created in thin gold films on a substrate. The advantage of using small apertures for terahertz microspectroscopy is that only terahertz light that has interacted with the cesium...

journal article 2013

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THz near-field Faraday imaging in hybrid metamaterials

Kumar, N. (author), Strikwerda, A.C. (author), Fan, K. (author), Zhang, X. (author), Averitt, R.D. (author), Planken, P.C.M. (author), Adam, A.J.L. (author)

We report on direct measurements of the magnetic near-field of metamaterial split ring resonators at terahertz frequencies using a magnetic field sensitive material. Specifically, planar split ring resonators are fabricated on a single magneto-optically active terbium gallium garnet crystal. Normally incident terahertz radiation couples to the...

journal article 2012

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Review of Near-Field Terahertz Measurement Methods and Their Applications: How to Achieve Sub-Wavelength Resolution at THz Frequencies

Adam, A.J.L. (author)

In the last decades, many research teams working at Terahertz frequencies focused their efforts on surpassing the diffraction limit. Numerous techniques have been investigated, combining methods existing at optic wavelength with THz system such as Time Domain Spectroscopy. The actual development led on one side to a resolution as high as ?/3000...

journal article 2011

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Terahertz near-field microspectroscopy

Knab, J.R. (author), Adam, A.J.L. (author), Chakkittakandy, R. (author), Planken, P.C.M. (author)

Using near-field, terahertz time-domain spectroscopy (THz-TDS), we investigate how the addition of a dielectric material into a subwavelength-diameter, cylindrical waveguide affects its transmission properties. The THz electric near-field is imaged with deep subwavelength resolution as it emerges from filled and unfilled waveguides....

journal article 2010

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Electromagnetic Spin-Orbit Interactions via Scattering of Subwavelength Apertures

Vuong, L.T. (author), Adam, A.J.L. (author), Brok, J.M. (author), Planken, P.C.M. (author), Urbach, H.P. (author)

Circularly polarized electric fields incident on subwavelength apertures produce near-field phase singularities with phase vorticity ±1 depending on the polarization handedness. These near-field phase singularities combine with those associated with orbital angular momentum and result in polarization-dependent transmission. We produce arbitrary...

journal article 2010

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Influence of the dielectric substrate on the terahertz electric near-field of a hole in a metal

Guestin, L. (author), Adam, A.J.L. (author), Knab, J.R. (author), Nagel, M. (author), Planken, P.C.M. (author)

We have studied theoretically and experimentally the influence of a dielectric substrate on the frequency-dependent terahertz electric near-field of a small hole in a metal layer. We find that the near-field transmission spectrum and the two-dimensional field distribution of an empty hole in a thin metal layer on a substrate are almost identical...

journal article 2009

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Terahertz Near-Field Vectorial Imaging of Subwavelength Apertures and Aperture Arrays

Knab, J.R. (author), Adam, A.J.L. (author), Nagel, M. (author), Shaner, E. (author), Seo, M.A. (author), Kim, D.S. (author), Planken, P.C.M. (author)

We present measurements of the complete terahertz (THz) electric near-field distribution, Ex, Ey and Ez, in both the time- and frequency-domains, for subwavelength apertures and subsections of subwavelength aperture arrays. Measuring the individual components of the THz near-field with subwavelength spatial resolution, as they emerge from these...

journal article 2009

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Bendable, low-loss Topas fibers for the terahertz frequency range

Nielsen, K. (author), Rasmussen, H.K. (author), Adam, A.J.L. (author), Planken, P.C.M. (author), Bang, O. (author), Jepsen, P.U. (author)

We report on a new class of polymer photonic crystal fibers for low-loss guidance of THz radiation. The use of the cyclic olefin copolymer Topas, in combination with advanced fabrication technology, results in bendable THz fibers with unprecedented low loss and low material dispersion in the THz regime.We demonstrate experimentally how the...

journal article 2009

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TeraHertz imaging of hidden paint layers on canvas

Adam, A.J.L. (author), Planken, P.C.M. (author), Meloni, S. (author), Dik, J. (author)

We show terahertz reflection images of hidden paint layers in a painting on canvas and compare the results with X-ray Radiography and Infrared Reflectography. Our terahertz measurements show strong reflections from both the canvas/paint interface and from the raw umber/lead white interface, indicating sufficient refractive-index contrast. Our...

journal article 2009

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Advanced terahertz electric near-field measurements at sub-wavelength diameter metallic apertures: Erratum

Adam, A.J.L. (author), Brok, J.M. (author), Seo, M.A. (author), Ahn, K.J. (author), Kim, D.S. (author), Kang, J.H. (author), Park, Q.H. (author), Nagel, M. (author), Planken, P.C.M. (author)

An erratum is presented to correct an error in the discussion section of [Opt. Express. 16, 7407-7417 (2008)] and to add a relevant reference on earlier work.

journal article 2008

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Near field imaging of terahertz focusing onto rectangular apertures

Seo, M.A. (author), Adam, A.J.L. (author), Kang, J.H. (author), Lee, J.W. (author), Ahn, K.J. (author), Park, Q.H. (author), Planken, P.C.M. (author), Kim, D.S. (author)

We performed terahertz near-field experiments on single rectangular holes with various lengths grown on an electro-optic crystal substrate with ?/100 resolution. We find that the near-field amplitude becomes proportionally larger as the rectangle becomes narrower, strongly suggesting that a constant energy passes through even for a very narrow...

journal article 2008

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Advanced terahertz electric near-field measurements at sub-wavelength diameter metallic apertures

Adam, A.J.L. (author), Brok, J.M. (author), Seo, M.A. (author), Ahn, K.J. (author), Kim, D.S. (author), Kang, J.H. (author), Park, Q.H. (author), Nagel, M. (author), Planken, P.C.M. (author)

Using terahertz-light excitation, we have measured with sub-wavelength spatial, and sub-cycle temporal resolution the time- and frequency-dependent electric-field and surface-charge density in the vicinity of small metallic holes. In addition to a singularity like concentration of the electric field near the hole edges, we observe, that holes...

journal article 2008

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Optical and terahertz near-field studies of surface plasmons in subwavelength metallic slits

Ahn, K.J. (author), Lee, K.G. (author), Kihm, H.W. (author), Seo, M.A. (author), Adam, A.J.L. (author), Planken, P.C.M. (author), Kim, D.S. (author)

journal article 2008

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Fourier-transform terahertz near-field imaging of one-dimensional slit arrays: Mapping of electric-field-, magnetic-field-, and Poynting vectors

Seo, M.A. (author), Adam, A.J.L. (author), Kang, J.H. (author), Lee, J.W. (author), Jeoung, S.C. (author), Park, Q.H. (author), Planken, P.C.M. (author), Kim, D.S. (author)

We present 2D measurements of the full THz electric field behind a sample consisting of multiple slits in a metal foil. Our measurements, which have a sub-wavelength spatial, and a sub-period temporal resolution, reveal electric field lines, electric field vortices and saddle points. From our measurements we are able to reconstruct the magnetic...

journal article 2007

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Measurement and calculation of the near field of a terahertz apertureless scanning optical microscope

Adam, A.J.L. (author), Van der Valk, N.C.J. (author), Planken, P.C.M. (author)

We present measurements and calculations of the terahertz (THz) electric field measured in the near field of a metal tip used in THz apertureless near-field optical microscopy (THz-ANSOM). An analytical model in which we treat the metal tip as a linear wire antenna allows us to predict almost all of the features observed in the measurements,...

journal article 2007