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

Adam, A.J.L.; Brok, J.M.; Seo, Mi Hae; Ahn, Kwang Jun; Kim, D. S.; Kang, Jong Soon; Park, Q. H.; Nagel, M.; Planken, Paul C. M.

doi:10.1364/oe.16.007407

Cited by 98 publications

(68 citation statements)

References 29 publications

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“…The high intensities will also become useful to perform THz probe measurements in the near-field (Chan et al, 2007;Keilmann et al, 2009) using, for instance, scanning near field techniques utilizing metallic tips Huber et al, 2009) or nanometer apertures (Adam et al, 2008;Seo et al, 2009). Near-field measurements promise to resolve an issue we have not addressed so far: THz spectroscopy is suitable to probe charge carrier dynamics in nanoscale systems.…”

Section: Discussionmentioning

confidence: 99%

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

et al. 2011

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Time-resolved, pulsed terahertz spectroscopy has developed into a powerful tool to study charge carrier dynamics in semiconductors and semiconductor structures over the past decades. Covering the energy range from a few to about 100 meV, terahertz radiation is sensitive to the response of charge quasiparticles, e.g., free carriers, polarons, and excitons. The distinct spectral signatures of these different quasiparticles in the THz range allow their discrimination and characterization using pulsed THz radiation. This frequency region is also well suited for the study of phonon resonances and intraband transitions in low-dimensional systems. Moreover, using a pump-probe scheme, it is possible to monitor the nonequilibrium time evolution of carriers and low-energy excitations with sub-ps time resolution. Being an all-optical technique, terahertz time-domain spectroscopy is contact-free and noninvasive and hence suited to probe the conductivity of, particularly, nanostructured materials that are difficult or impossible to access with other methods. The latest developments in the application of terahertz time-domain spectroscopy to bulk and nanostructured semiconductors are reviewed.

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Section: Discussionmentioning

confidence: 99%

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

et al. 2011

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“…We experimentally measure the scattered longitudinalfield components from subwavelength apertures using a THz near-field electro-optic detection method and focused probe beam, which provides full vector characterization of the transmitted shadowside electric-field with 10 m resolution [22]. From the response to an incident linearlypolarized THz field and using the principle of superposition, we numerically reconstruct the response due to a circularly-polarized incident field.…”

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confidence: 99%

Electromagnetic Spin-Orbit Interactions via Scattering of Subwavelength Apertures

et al. 2010

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Circularly polarized electric fields incident on subwavelength apertures produce near-field phase singularities with phase vorticity AE1 depending on the polarization handedness. These near-field phase singularities combine with those associated with orbital angular momentum and result in polarizationdependent transmission. We produce arbitrary phase vorticity in the longitudinal component of scattered electric fields by varying the incident beam and aperture configuration. DOI: 10.1103/PhysRevLett.104.083903 PACS numbers: 42.25.Fx, 42.25.Gy, 42.25.Ja, 42.50.Tx Phase singularities in the electric field are locations at which the field amplitude is strictly zero. Given a fixed polarization or ''spin'', the phase integral over the transverse field components enclosing a phase singularity provides a measure of the phase vorticity or orbital angular momentum (OAM) topological charge [1,2]. The threedimensional electric field of an inhomogeneously polarized propagating electromagnetic wave produces three different types of polarization phase singularities [3], the evolution of which is studied in a rich array of literature [4]. Our understanding of phase singularities allows us to probe materials, characterize surfaces, study light propagation dynamics, and manipulate microparticles [5].Within the last decade, there have been observations of near-field phase singularities (NFPS) in the evanescent waves produced by propagating [6] and scattered [7] light. The locations of NFPS produced by chiral ''gammadion' ' [8] and spiral grating structures [9] depend on incident polarization handedness. These NFPS are connected to the extraordinary transmission of light through subwavelength slits [10], where whirlpool-like power flows and singularities in the Poynting vector are shown to exist [11,12]. Azimuthally and radially polarized vortices, beams with different polarization singularities, are transmitted through apertures with different efficiencies [13] but in spite of numerous measurements and observations of NFPS, the polarization-dependent transmission that occurs at subwavelength structures is not fully understood and light-metal interactions are neither fully optimized nor controlled.Here, we show that the polarization-dependent transmission at sub-wavelength-structured materials are concisely explained by a coupling between electromagnetic spin and OAM. ''Spin-orbit interactions'' describe the modified light propagation due to their coupling where the longitudinal component of an electric field generally plays a crucial role. It has been shown that spin-orbit interactions occur via oblique reflections and refraction [14], in wave guiding structures [15], and in the focal plane of highly focused beams [16]. In these situations, a change in either the direction of the phase vorticity or the polarization handedness results in a shift of the observed light intensity patterns.Our work explains, for the first time, that polarizationdependent NFPS describe which modes and to what extent light is transmitted through th...

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“…The highest resolution has been achieved by Huber et al with a resolution of λ/3000 at 2.54 THz using a single frequency source and a scattering tip [8]. For broadband system based on single-cycle pulsed source, the resolution obtained is in the region of λ/600 [9,10] with separate mapping of the different components of the electric near-field with its amplitude and phase. Commercial systems are currently available http://www.amo.de/?id=687.…”

Section: Motivation and State Of The Artmentioning

confidence: 99%

“…They can only measure the electric near-field in one plane, but they avoid the presence of a gap that would influence the measurement. They've measured the full THz electric near-field emerging from a single aperture deposited on the EO crystal [9].…”

Section: Direct Detection In the Near-fieldmentioning

confidence: 99%

“…Remarkable results like the fact that the hole differentiates the incident field, waited to be measured. In 2008, Adam et al, using an EO crystal underneath a hole made of a deposited gold layer, compared successfully the Bouwkamp's model with the measurement of the THz light emerging from the subwavelength hole [9]. They could especially measure the component perpendicular to the metal sheet, i.e.…”

Section: Aperturesmentioning

confidence: 99%

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Review of Near-Field Terahertz Measurement Methods and Their Applications

Adam

2011

J Infrared Milli Terahz Waves

198

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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 λ/3000 and one the other side to a video-rate recording. The purpose of this paper is to give an overview of the history of the field, to describe the different approaches, to give examples of existing applications and to draw the perspective for this research area.

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

Cited by 98 publications

References 29 publications

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

Electromagnetic Spin-Orbit Interactions via Scattering of Subwavelength Apertures

Review of Near-Field Terahertz Measurement Methods and Their Applications

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