Enrique Castro-Camus
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View article: Diffraction effects in highly defocused THz beams
Diffraction effects in highly defocused THz beams Open
Terahertz communication links will require the use of directional beams to compensate for the higher losses compared to those faced in the few gigahertz region. The shorter wavelengths of terahertz waves also imply less diffraction from ob…
View article: The dynamics of stomatal closure of Arabidopsis thaliana determined by terahertz spectroscopy and a water transport model
The dynamics of stomatal closure of Arabidopsis thaliana determined by terahertz spectroscopy and a water transport model Open
Terahertz (THz) time-domain spectroscopy allows the detection of temporal changes of plant water content in vivo and non-destructively, for example over the course of the day or at the onset of drought stress. By studying a wildtype and a …
View article: Rh-doped, InGaAs-based Quantum-Photoconductor with Superior Carrier Mobility-Lifetime Trade-off for THz Time-Domain Spectroscopy
Rh-doped, InGaAs-based Quantum-Photoconductor with Superior Carrier Mobility-Lifetime Trade-off for THz Time-Domain Spectroscopy Open
Photoconductive antennas (PCAs) are key elements for the implementation of fiber-coupled terahertz (THz) time-domain spectroscopy (TDS) systems as they provide high infrared-to-THz conversion efficiency. However, their performance is funda…
View article: Sparse Terahertz Frequency-Domain Sensing with Kilohertz Measurement Rate
Sparse Terahertz Frequency-Domain Sensing with Kilohertz Measurement Rate Open
The widespread industrial application of terahertz spectroscopy is currently constrained by system complexity, high costs, and limited measurement rates. Optoelectronic frequency-domain spectroscopy (FDS) offers a promising approach to mit…
View article: Computationally efficient multi-layer thickness determination using sparse CW THz spectroscopy
Computationally efficient multi-layer thickness determination using sparse CW THz spectroscopy Open
Continuous wave (CW) terahertz spectroscopy systems are a proven and convenient solution for industrial non-destructive testing and multi-layer thickness determination. For these systems to find use in real-time inline monitoring applicati…
View article: Automated in-situ monitoring of accelerated crystallization processes of nifedipine using terahertz time-domain spectroscopy
Automated in-situ monitoring of accelerated crystallization processes of nifedipine using terahertz time-domain spectroscopy Open
We developed and tested an automated measurement platform which can fit multiple samples for their investigation in transmission mode using terahertz time-domain spectroscopy. The temperature inside the platform can be varied to simulate d…
View article: Terahertz time-domain imaging for the examination of gilded wooden artifacts
Terahertz time-domain imaging for the examination of gilded wooden artifacts Open
Terahertz imaging is unlocking unique capabilities for the analysis of cultural heritage artifacts. This paper uses terahertz time-domain imaging for the study of a gilded wooden artifact, providing a means to perform stratigraphic analysi…
View article: Roadmap on optical sensors
Roadmap on optical sensors Open
Optical sensors and sensing technologies are playing a more and more important role in our modern world. From micro-probes to large devices used in such diverse areas like medical diagnosis, defence, monitoring of industrial and environmen…
View article: Terahertz Spectroscopy for Non-Destructive Solid-State Investigation of Norfloxacin in Paper Tablets after Wet Granulation
Terahertz Spectroscopy for Non-Destructive Solid-State Investigation of Norfloxacin in Paper Tablets after Wet Granulation Open
(1) Background: Amorphous drug systems are an intensively studied approach to overcome the insufficient bioavailability of poorly soluble drugs. Here, paper tablets were studied, which were made from cellulose-based paper matrices loaded w…
View article: Transmission, Reflection, and Scattering Characterization of Building Materials for Indoor THz Communications
Transmission, Reflection, and Scattering Characterization of Building Materials for Indoor THz Communications Open
The future communication technologies are naturally evolving towards higher carrier frequencies in order to satisfy the demand for increasing data rates. Terahertz frequencies appear to make high speed and high data rate communications pos…
View article: The 2023 terahertz science and technology roadmap
The 2023 terahertz science and technology roadmap Open
Terahertz (THz) radiation encompasses a wide spectral range within the electromagnetic spectrum that extends from microwaves to the far infrared (100 GHz–∼30 THz). Within its frequency boundaries exist a broad variety of scientific discipl…
View article: Temperature dependence of the dielectric function of dehydrated biological samples in the THz band
Temperature dependence of the dielectric function of dehydrated biological samples in the THz band Open
Terahertz technology has demonstrated enormous potential for the analysis of biological systems and the diagnosis of some medical conditions, given its high sensitivity to detect water content. In previously published papers, effective med…
View article: Algorithm for Determination of Cutoff Frequency of Noise Floor Level for Terahertz Time-Domain Signals
Algorithm for Determination of Cutoff Frequency of Noise Floor Level for Terahertz Time-Domain Signals Open
The frequency-dependent signal-to-noise ratio of terahertz time-domain signals is a relevant source of uncertainty for parameters measured with it. It also limits the total usable bandwidth of such signals. In the great majority of cases, …
View article: Achromatic Quarter-Waveplate for the Terahertz Frequency Range Made by 3D Printing
Achromatic Quarter-Waveplate for the Terahertz Frequency Range Made by 3D Printing Open
Here we propose a 3D printed form-birefringent achromatic quarter-waveplate targeting the lower terahertz frequency range. The monolithically fabricated waveplate consists of three individual layers of different thickness and orientation o…
View article: Non-destructive crystallinity assessment of indomethacin in tablets made from smartFilms® using terahertz time-domain spectroscopy
Non-destructive crystallinity assessment of indomethacin in tablets made from smartFilms® using terahertz time-domain spectroscopy Open
We use terahertz (THz) time-domain spectroscopy (TDS) to assess the crystalline state of indomethacin (IM) when loaded in smartFilms®. We found that smartFilms favour the amorphous IM (A-IM) for low loading concentrations. For higher conce…
View article: Terahertz (THz) biophotonics technology: Instrumentation, techniques, and biomedical applications
Terahertz (THz) biophotonics technology: Instrumentation, techniques, and biomedical applications Open
Terahertz (THz) technology has experienced rapid development in the past two decades. Growing numbers of interdisciplinary applications are emerging, including materials science, physics, communications, and security as well as biomedicine…
View article: Terahertz referenceless wavefront sensing by means of computational shear-interferometry
Terahertz referenceless wavefront sensing by means of computational shear-interferometry Open
In this contribution, we demonstrate the first referenceless measurement of a THz wavefront by means of shear-interferometry. The technique makes use of a transmissive Ronchi phase grating to generate the shear. We fabricated the grating b…
View article: Recent advances in terahertz imaging: 1999 to 2021
Recent advances in terahertz imaging: 1999 to 2021 Open
We discuss the progress in the field of THz imaging based on time-domain spectroscopy during the last 20 years emphasizing several highlights. These include 3D mapping of the water distribution of plants, THz reflection imaging of samples …
View article: Terahertz emission from gradient InGaAs surfaces
Terahertz emission from gradient InGaAs surfaces Open
We present an experimental study of the terahertz emission from InxGa1−xAs epitaxial layers that were grown while varying the alloy fraction x. We observe the terahertz emission that is significantly different depending on the variation di…
View article: Nonlocal Time-Resolved Terahertz Spectroscopy in the Near Field
Nonlocal Time-Resolved Terahertz Spectroscopy in the Near Field Open
Scattering-type near-field optical microscopy (s-SNOM) has enabled subwavelength spectroscopy measurements on a wide variety of materials and over a large spectral range. These tip-based measurements are of particular interest in the long …