Electro-optic detection of subwavelength terahertz spot sizes in the near field of a metal tip

Valk, N. C. J. van der; Planken, Paul C. M.

doi:10.1063/1.1503404

Cited by 203 publications

(81 citation statements)

References 15 publications

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“…Such strategy has been first employed by Planken's group in 2002 [45]. As a detector they used an electro-optical (EO) crystal such as GaP on which they deposit the sample.…”

Section: Metal Tip-near-f Ield Collectionmentioning

confidence: 99%

“…Schematic for the tip scattering method: a Collection in the near-field: an EO crystal is placed underneath the tip. Only the component of the electric field parallel to the probe propagation direction will be measured [45]. b Collection in the far field: the forward scattered field is directly measured in the far field.…”

Section: Metal Tip-near-f Ield Collectionmentioning

confidence: 99%

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Review of Near-Field Terahertz Measurement Methods and Their Applications

Adam

2011

J Infrared Milli Terahz Waves

202

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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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“…Such strategy has been first employed by Planken's group in 2002 [45]. As a detector they used an electro-optical (EO) crystal such as GaP on which they deposit the sample.…”

Section: Metal Tip-near-f Ield Collectionmentioning

confidence: 99%

Section: Metal Tip-near-f Ield Collectionmentioning

confidence: 99%

Review of Near-Field Terahertz Measurement Methods and Their Applications

Adam

2011

J Infrared Milli Terahz Waves

202

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“…Details of these setups can be found in Refs. [4][5][6]. The difference between the setups shown in Figs.…”

mentioning

confidence: 99%

“…Very recently, there have been reports showing how ANSOM can be adapted for the terahertz (THz) frequency domain, by combining it with THz time-domain spectroscopy. [4][5][6][7] This is an exciting development, as it is becoming increasingly clear that many systems of interest, including biological molecules and a variety of artificial nanostructures, have absorption features in the THz frequency range, but are far smaller than the wavelength of the THz radiation. [8][9][10][11] These developments therefore offer great promise for THz microscopy.…”

mentioning

confidence: 99%

Antenna effects in terahertz apertureless near-field optical microscopy

Wang

Mittleman

Valk

et al. 2004

Applied Physics Letters

126

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We have performed measurements on terahertz (THz) apertureless near-field microscopy that show that the temporal shape of the observed near-field signals is approximately proportional to the time-integral of the incident field. Associated with this signal change is a bandwidth reduction by approximately a factor of 3 which is observed using both a near-field detection technique and a far-field detection technique. Using a dipole antenna model, it is shown how the observed effects can be explained by the signal filtering properties of the metal tips used in the experiments. Apertureless near-field scanning optical microscopy (ANSOM) is an attractive technique for obtaining subwavelength resolution in optical imaging at visible and midinfared wavelengths. [1][2][3] In this technique, light is scattered off a subwavelength-sized metal tip which is held close to a surface. The scattered light is collected in the far-field, giving subwavelength resolution in the immediate neighborhood of the tip apex. Very recently, there have been reports showing how ANSOM can be adapted for the terahertz (THz) frequency domain, by combining it with THz time-domain spectroscopy. [4][5][6][7] This is an exciting development, as it is becoming increasingly clear that many systems of interest, including biological molecules and a variety of artificial nanostructures, have absorption features in the THz frequency range, but are far smaller than the wavelength of the THz radiation. [8][9][10][11] These developments therefore offer great promise for THz microscopy. In the THz ANSOM experiments, two different detection techniques are currently employed: THz electric fields are either detected in the nearfield of the tip using electro-optic sampling, or in the far-field of the tip with a receiver. In the latter case, near-field information from the tip apex is obtained by vibrating the metal tip at a high frequency, followed by phase-sensitive detection at this frequency. However, an important aspect of both experiments remains unexplained: The measured temporal profile of the near-field signals is very different from that of the incident THz pulses. Associated with this shape change is a bandwidth reduction of about a factor of 3, which could limit the utility of the technique in spectroscopic measurements. For practical applications, such as THz microscopy, it is essential that the origin of this bandwidth reduction is understood.Here, we present measurements and calculations which demonstrate that the observed bandwidth reduction is a consequence of the antenna properties of the metal tips used in the experiments. We demonstrate that, regardless of whether the near-field signal is observed directly under the tip or in the far-field, it is approximately proportional to the timeintegral of the incident THz signal. Near-field calculations based on a dipole antenna model qualitatively reproduce all the essential features observed in the measurements and provide insight into ANSOM experiments in general.The two THz ANSOM configurations, used ...

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“…In the terahertz (THz) region, subwavelength resolution of the order of 0.01 wavelength has been achieved using scanning near-field imaging. 25,26) However, for applications such as particle tracking, a nonscanning method is desirable.…”

mentioning

confidence: 99%

One-dimensional subwavelength position determination exploiting off-axis parabolic mirror

Shibata

Uemoto

2017

Appl. Phys. Express

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We demonstrate a subwavelength position determination method for the terahertz region. Previously, we reported that an off-axis parabolic mirror generates a peculiar transient rotational distribution around the focus on the subwavelength scale. In the method proposed herein, the position is determined by measuring the electric field scattered by a sample placed at this rotational distribution. We perform a realistic numerical calculation and show that this method is feasible for a sample on the wavelength scale and can distinguish a displacement of the order of 0.01 wavelengths. This method can be easily implemented for micro and nanoscale measurement and processing in the terahertz region.

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Electro-optic detection of subwavelength terahertz spot sizes in the near field of a metal tip

Cited by 203 publications

References 15 publications

Review of Near-Field Terahertz Measurement Methods and Their Applications

Review of Near-Field Terahertz Measurement Methods and Their Applications

Antenna effects in terahertz apertureless near-field optical microscopy

One-dimensional subwavelength position determination exploiting off-axis parabolic mirror

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