Full vectorial mapping of the complex electric near-fields of THz resonators

Bhattacharya, Arkabrata; Rivas, J Jaime Gómez

doi:10.1063/1.4962905

Cited by 35 publications

(19 citation statements)

References 46 publications

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“…[31][32][33] The THz near-field microscope used in our experiments is schematically depicted in Figure 4a, and has been also described previously. [34][35][36] Similar to the far-field measurements presented earlier, a THz microprobe (Protemics GmbH) is used to detect the polarization dependent electric near-field at a distance of 0.5 μm above the sample. [37] The detected polarization is the same as the incident polarization.…”

Section: Terahertz Near-field Microscopymentioning

confidence: 99%

Terahertz Time‐Domain Spectroscopy and Near‐Field Microscopy of Transparent Silver Nanowire Networks

Hoof

Parente

Baldi

et al. 2019

Advanced Optical Materials

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spin-coating to spray-coating, electrospinning, and dip coating. [3,6,7] Furthermore, large-area lithography and metal coating techniques are increasingly emerging as promising alternatives. [8][9][10] However, it is not uncommon for these deposition techniques to result in a conductance that varies spatially due to local modulations in the network thickness or connectivity. These spatial modulations of the electrical conductance are impossible to detect with standard characterization techniques such as the four-point probe method, in which the electrical impedance is measured using a pair of separated electrodes carrying a current and sensing the voltage differences. Furthermore, although microprobes have been developed to map the conductance with high spatial resolution, [11] the four-point probe technique requires electrical contact with the surface, leading to the risk of modifying the sample. These limitations highlight the need for a contact-free and high resolution technique to map electrical conductance over large areas. Broadband and phase sensitive spectroscopic techniques, such as terahertz time-domain spectroscopy (THz-TDS), have emerged as powerful alternatives for probing the complex conductivity of samples. [12][13][14][15] THz-TDS uses very short (single cycle) electromagnetic pulses as low frequency electromagnetic probes to measure the electronic properties. This probing is done by measuring the attenuation and the phase of the THz pulse as it propagates through the medium and interacts (mainly) with free charge carriers. A major advantage of THz-TDS over four-point probe techniques is that it is a contact free technique, which also enables an easy implementation of conductivity scans. The diffraction limit of electromagnetic waves (on the order of the wavelength) defines the maximum spatial resolution that can be attained for the determination of the conductivity using far-field THz techniques. The broadband character of THz-TDS and the standard focusing optics, with relatively low numerical aperture, leads to spatial resolutions on the order of 1 mm or larger.In this manuscript, we synthesize highly monodisperse AgNWs with a diameter of ≈50 nm and a length of ≈10 μm by adapting a polyol method. [16] Subsequently, transparent electrodes are prepared by spray coating the AgNWs solution on top of 25 × 25 mm 2 quartz substrates. The nanowire monodispersity allows us to draw quantitative conclusions from the measurements performed on the conductive networks. We spatially vary the thickness of the AgNWs network across the quartz substrate, and therefore its optical transmission and THz conductance, by adjusting the spray coating conditions. Transparent conductive layers are key components of optoelectronic devices. Here, a polyol method is used to synthesize large quantities of monodisperse silver nanowires (AgNWs) and these are used to fabricate transparent conducting networks over large areas. The optical extinction and terahertz (THz) conductance of these networks are simultaneously investigated,...

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Section: Terahertz Near-field Microscopymentioning

confidence: 99%

Terahertz Time‐Domain Spectroscopy and Near‐Field Microscopy of Transparent Silver Nanowire Networks

Hoof

Parente

Baldi

et al. 2019

Advanced Optical Materials

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“…Studying the interaction of THz radiation with sub-diffraction structures requires near-field measurements. The THz near-field microscope used for our measurements has been described previously, 46,47 where THz microprobes (Protemics GmbH) are used to detect the polarization dependent electric near-field at a distance of 0.5 µm above the sample. The spatially and temporally resolved near-fields are collected by raster scanning the sample through the optical axis defined by the incident THz beam and the near-field microprobe.…”

Section: Near-field Microscopymentioning

confidence: 99%

Diffraction Enhanced Transparency in a Hybrid Gold-Graphene THz Metasurface

Huurne

Hoof

Vervuurt

et al. 2018

2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)

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“…As an alternative method, near-field electro-optic and magneto-optic sampling was used to investigate THz antennas and split-ring resonators [9][10][11]. Micro-fabricated commercial THz photoconductive switches were utilized recently to map vector fields near a dipole antenna [12]. These near-field techniques also enable time-resolved mapping of the THz field, which can provide insight into the process of resonator excitation [13].…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy and mapping of resonant fields in terahertz plasmonic resonators

et al. 2017

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Plasmonic terahertz (THz) resonators provide a promising route for exploring strong light-matter coupling phenomena. Double-metal resonator designs in particular enable strong enhancement of the THz field and provide well-defined field orientation and confinement within a sub-wavelength size volume. The strong field confinement however limits access to the internal fields essential for investigations of light-matter coupling. We propose and investigate a method for mapping and spectroscopic analysis of the internal fields in double-metal plasmonic THz resonators. We use aperture-type scanning near-field THz microscopy to access strongly confined fields with sub-wavelength spatial resolution of ~5 μm (~λ/100). Combined with the THz time-domain spectroscopy technique, the near-field method allows us to perform spectroscopic studies and investigate the field evolution inside the resonator. This experimental method opens doors to studies of strong light-matter coupling at THz frequencies in individual plasmonic resonators.

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Full vectorial mapping of the complex electric near-fields of THz resonators

Cited by 35 publications

References 46 publications

Terahertz Time‐Domain Spectroscopy and Near‐Field Microscopy of Transparent Silver Nanowire Networks

Terahertz Time‐Domain Spectroscopy and Near‐Field Microscopy of Transparent Silver Nanowire Networks

Diffraction Enhanced Transparency in a Hybrid Gold-Graphene THz Metasurface

Spectroscopy and mapping of resonant fields in terahertz plasmonic resonators

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