Sub-wavelength terahertz imaging through optical rectification

Sanjuan, Federico; Gaborit, Gwenaël; Coutaz, Jean‐Louis

doi:10.1038/s41598-018-31970-w

Cited by 14 publications

(8 citation statements)

References 30 publications

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“…To overcome this limit, different approaches in improving the resolution to sub-THz wavelengths were proposed, e.g., using near-field techniques, generating the THz signal at the surface of the investigated sample, detection of THz by very small probes, computational imaging methods, etc. [47,48,49]. By using these techniques, spatial resolutions in nanometer range were achieved.…”

Section: Methodsmentioning

confidence: 99%

Spectroscopic Analysis of Melatonin in the Terahertz Frequency Range

Puc

Abina

Jeglic

et al. 2018

Sensors

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There is a need for fast and reliable quality and authenticity control tools of pharmaceutical ingredients. Among others, hormone containing drugs and foods are subject to scrutiny. In this study, terahertz (THz) spectroscopy and THz imaging are applied for the first time to analyze melatonin and its pharmaceutical product Circadin. Melatonin is a hormone found naturally in the human body, which is responsible for the regulation of sleep-wake cycles. In the THz frequency region between 1.5 THz and 4.5 THz, characteristic melatonin spectral features at 3.21 THz, and a weaker one at 4.20 THz, are observed allowing for a quantitative analysis within the final products. Spectroscopic THz imaging of different concentrations of Circadin and melatonin as an active pharmaceutical ingredient in prepared pellets is also performed, which permits spatial recognition of these different substances. These results indicate that THz spectroscopy and imaging can be an indispensable tool, complementing Raman and Fourier transform infrared spectroscopies, in order to provide quality control of dietary supplements and other pharmaceutical products.

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Section: Methodsmentioning

confidence: 99%

Spectroscopic Analysis of Melatonin in the Terahertz Frequency Range

Puc

Abina

Jeglic

et al. 2018

Sensors

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“…Since these typically have wavelengths in the NIR, they can be focused to a diffraction-limited spot much smaller than THz frequency pulses, giving an improved imaging resolution by more than two orders of magnitude [145]. For example, integrated circuits have been imaged with a spatial resolution down to 1 µm [146], but the method has also been used to study physical processes in THz radiating materials [147][148][149][150][151][152] or processes on the surface of the radiating semiconductor [153][154][155]. Recently, the spatial resolution of LTEM was improved even further by implementing it in an s-SNOM microscope where a gold nanorod was imaged on a THz radiating InAs substrate (Figure 11) [156].…”

Section: Variations Of S-snom Configuration For Thz Imagingmentioning

confidence: 99%

Terahertz Field Confinement in Nonlinear Metamaterials and Near-Field Imaging

Keiser

Klarskov

2019

Photonics

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This article reviews recent advances in terahertz science and technology that rely on confining the energy of incident terahertz radiation to small, very sub-wavelength sized regions. We focus on two broad areas of application for such field confinement: metamaterial-based nonlinear terahertz devices and terahertz near-field microscopy and spectroscopy techniques. In particular, we focus on field confinement in: terahertz nonlinear absorbers, metamaterial enhanced nonlinear terahertz spectroscopy, and in sub-wavelength terahertz imaging systems.

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“…Recently, Sotome et al 6 employed OR in transmission to obtain THz images of ferroelectric samples, where the laser beam was scanned over the sample, and each irradiated point of the sample generated a THz signal whose magnitude was related to both the crystallinity and nonlinearity of the sample. More recently, some of us used the same technique to get THz images of a caster sugar grain with a sub-wavelength resolution 7 . We named this technique Optical Rectification Terahertz Imaging (ORTI).…”

Section: Introductionmentioning

confidence: 99%

Terahertz generation through optical rectification in reflection

Kristensen

Hérault

Zhai

et al. 2023

Journal of Applied Physics

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In this paper, we study terahertz generation through optical rectification in reflection at normal incidence in a dielectric nonlinear crystal. We first analyze, with a nonlinear optical model, the sample parameters (thickness, absorption at both laser and terahertz wavelengths, etc.) for which a terahertz optical rectification reflection scheme is preferable to the common transmission scheme. Then, we report our experimental observations of a reflected terahertz signal generated at the surface of a ZnTe crystal. The reflected terahertz signal shares all the characteristics of a signal generated in transmission but is not limited by absorption losses in the crystal, thereby providing a broader bandwidth. At high pump laser power, the signal exhibits saturation, which is caused by the decrease of the nonlinear susceptibility due to photocarriers generated by two-photon absorption. This reflection scheme could be of great importance for terahertz microscopy of opaque materials like, e.g., humid samples or samples exhibiting strong absorption bands or to study samples for which the transmitted signal cannot be recorded.

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Sub-wavelength terahertz imaging through optical rectification

Cited by 14 publications

References 30 publications

Spectroscopic Analysis of Melatonin in the Terahertz Frequency Range

Spectroscopic Analysis of Melatonin in the Terahertz Frequency Range

Terahertz Field Confinement in Nonlinear Metamaterials and Near-Field Imaging

Terahertz generation through optical rectification in reflection

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