Spectroscopic THz near-field microscope

Abstract:We investigated the excitation of surface plasmon polaritons on gold films with the metallized probe tip of a scattering-type scanning near-field optical microscope (s-SNOM). The emission of the polaritons from the tip, illuminated by near-infrared laser radiation, was found to be anisotropic and not circularly symmetric as expected on the basis of literature data. We furthermore identified an additional excitation channel via light that was reflected off the tip and excited the plasmon polaritons at the edge of the metal film. Our results, while obtained for a non-rotationally-symmetric type of probe tip and thus specific for this situation, indicate that when an s-SNOM is employed for the investigation of plasmonic structures, the unintentional excitation of surface waves and anisotropic surface wave propagation must be considered in order to correctly interpret the signatures of plasmon polariton generation and propagation.

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“…[15,16], as well as for the first demonstration of a time-domain THz s-SNOM [17]. A scheme of the set-up is shown in Figure 1A.…”

Section: Methodsmentioning

confidence: 99%

Anisotropic excitation of surface plasmon polaritons on a metal film by a scattering-type scanning near-field microscope with a non-rotationally-symmetric probe tip

et al. 2017

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“…In the right plot of Fig. 21, Ribbeck et al give an example of the calculation of amplitude contrasts of the field scattered from a tip above a Si surface with different doping concentration [51]. One can see that at a fixed frequency, such as 1 THz, a strong contrast is expected between doping concentrations in the range of 10 17 -10 19 cm −3 .…”

Section: Inspectionmentioning

confidence: 96%

Review of Near-Field Terahertz Measurement Methods and Their Applications

Adam

2011

J Infrared Milli Terahz Waves

197

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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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“…2 clear evidence was established of attaining the pure near-field interaction: the contrast between materials was of the order of 100%; the tip-sample approach induced a signal change compatible with the 200-300 nm size of the home-made tip used; and the spectra of near-field contrast agreed with the model prediction and distinctly distinguished a metallic from a lowly-doped semiconductor sample [41]. Note these near-field spectra were truely broadband, covering four octaves from 0.1 to 3 THz, but unfortunately the weak scattered signal (note the source emits typically several µW of THz power) necessitated 19 min observation time for each spectrum such that scanning an image was not practical.…”

Section: Apertureless Near-field Microscopy Development From Microwavmentioning

confidence: 56%

“…6 is probably owed to an obvious moment of non-repeatability in quantitative s-SNOM: when repeatedly recording an image one can often notice a slight drift of the sample; also an abrasion or other deterioration of the probing tip might occur; and when changing the wavelength minute beam directional changes might happen [33]. To overcome these effects spectroscopic s-SNOM has been initiated in which a broad band of frequencies is applied and read out simultaneously, such that a near-field spectrum is obtained at each pixel while scanning [26,41].…”

Section: Apertureless Near-field Microscopy Development From Microwavmentioning

confidence: 99%

Nanoscale Conductivity Contrast by Scattering-Type Near-Field Optical Microscopy in the Visible, Infrared and THz Domains

Keilmann

Huber

Hillenbrand

2009

J Infrared Milli Terahz Waves

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We demonstrate the wide application potential of optical near-field microscopy for mapping samples with locally varying conductivity. The apertureless, scattering-type optical near-field microscope (s-SNOM) operates on an AFM basis with an added lightscattering channel, wherein a standard cantilevered tip suffices to accomodate the full spectral range from visible to THz frequencies. The optical maps appear in amplitude and phase contrast, simultaneously with the topography map, at a spatial resolution of typically 20 nm. Visible and near-infrared operation is best suited for distinguishing metals, while a sensitive response to semiconductors is ideally provided with infrared and THz operation. Various types of conductivity spectral features can be explored in specific regions, corresponding to the elementary excitation linked to e.g. superconductivity, electron correlation, or low-dimensional conduction.

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Spectroscopic THz near-field microscope

Cited by 135 publications

References 41 publications

Anisotropic excitation of surface plasmon polaritons on a metal film by a scattering-type scanning near-field microscope with a non-rotationally-symmetric probe tip

Anisotropic excitation of surface plasmon polaritons on a metal film by a scattering-type scanning near-field microscope with a non-rotationally-symmetric probe tip

Review of Near-Field Terahertz Measurement Methods and Their Applications

Nanoscale Conductivity Contrast by Scattering-Type Near-Field Optical Microscopy in the Visible, Infrared and THz Domains

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