arXiv subjects

Mirco Kutas

Publications and source records attributed to Mirco Kutas.

7 recordsLinked to original sources

arXiv2026

Accessibility of doping ranges of semiconductors by terahertz spectroscopy

While established semiconductor measurement techniques such as four-point probe or capacitance-voltage measurements require a physical contact to the material, terahertz spectroscopy is completely contact-free. Its capability to measure the doping of semiconductors is well known, yet the exact doping ranges that are accessible to terahertz spectroscopy are not obvious. Therefore, we introduce a sensitivity metric to clarify whether a semiconductor sample can be characterized in principle by reflection terahertz time-domain spectroscopy. This quantity takes into account the semiconductor material with a certain layer thickness, doping type, and doping level and is based on numerical simulations. In this work, we calculate this sensitivity value for relevant semiconductor materials (SiC, Si, GaN) in realistic layer stacks with up to three layers. It is used to create meaningful heat maps depending on the thicknesses and charge carrier densities of the sample structures of interest. The plausibility of the sensitivity is validated by mapping a variety of measurements with terahertz techniques from us and from other groups onto these heat maps. Based on these, the accessible range of charge carrier densities for terahertz spectroscopy spans roughly from 10$^{15}$ cm$^{-3}$ to 10$^{20}$ cm$^{-3}$, but with dependencies on material, doping type, and sample thickness. Furthermore, the sensitivity value allows for a substantiated assessment of the possible benefits future improvements of photoconductive antennas and terahertz systems could have, which is demonstrated by simulations based on varied bandwidths.

physics.optics↗

arXiv2024

Terahertz Quantum Imaging

Quantum imaging with undetected photons spatially transfers amplitude and phase information from one spectral region of physical interest to another spectral region that is easy to detect. The photon energy of the two spectral regions can, in principle, be separated by several orders of magnitude. However, quantum imaging with undetected photons has so far only been demonstrated in spectral regions of similar order of magnitude in frequency (and for which cameras are commercially available). Here, we demonstrate amplitude- and phase-sensitive imaging in the terahertz spectral region (1.5 THz center frequency) by detecting only visible photons (center wavelength 662.2 nm, 452.7 THz center frequency) more than two orders of magnitude apart. As a result, terahertz spectral information can be reliably detected with a standard CMOS camera without cooling, achieving a spatial resolution close to the wavelength. By taking advantage of quantum distillation in a nonlinear interferometer, the influence of ubiquitous thermal terahertz photons can be neglected. Our results are in good agreement with numerical simulations of the imaging process and demonstrate the huge potential of this method to address otherwise challenging spectral regions where cameras do not exist.

quant-ph↗

arXiv2022

General simulation method for quantum-sensing systems

Quantum sensing encompasses highly promising techniques with diverse applications including noise-reduced imaging, super-resolution microscopy as well as imaging and spectroscopy in challenging spectral ranges. These detection schemes use biphoton correlations to surpass classical limits or transfer information to different spectral ranges. Theoretical analysis is mostly confined to idealized conditions. Therefore, theoretical predictions and experimental results for the performance of quantum-sensing systems often diverge. Here we present a general simulation method that includes experimental imperfections to bridge the gap between theory and experiment. We develop a theoretical approach and demonstrate the capabilities with the simulation of aligned and misaligned quantum-imaging experiments. The results recreate the characteristics of experimental data. We further use the simulation results to improve the obtained images in post-processing. As simulation method for general quantum-sensing systems, this work provides a first step towards powerful simulation tools for interactively exploring the design space and optimizing the experiment's characteristics.

quant-ph↗

arXiv2022

General simulation method for spontaneous parametric down- and parametric up-conversion experiments

Spontaneous parametric down-conversion (SPDC) sources are an important technology for quantum sensing and imaging. We demonstrate a general simulation method, based on modeling from first principles, reproducing the spectrally and spatially resolved absolute counts of a SPDC experiment. By simulating additional processes and effects we accomplish good agreement with the experimental results. This method is broadly applicable and allows for the separation of contributing processes, virtual characterization of SPDC sources, and enables the simulation of many quantum based applications.

quant-ph↗

arXiv2022

Phase-quadrature quantum imaging with undetected photons

Sensing with undetected photons allows access to spectral regions with simultaneous detection of photons of another region and is based on nonlinear interferometry. To obtain the full information of a sample, the corresponding interferogram has to be analyzed in terms of amplitude and phase, which has been realized so far by multiple measurements followed by phase variation. Here, we present a polarization-optics-based phase-quadrature implementation in a nonlinear interferometer for imaging with undetected photons in the infrared region. This allows us to obtain phase and visibility with a single image acquisition without the need of varying optical paths or phases, thus enabling the detection of dynamic processes. We demonstrate the usefullness of our method on a static phase mask opaque to the detected photons as well as on dynamic measurement tasks as the drying of an isopropanol film and the stretching of an adhesive tape.

quant-ph↗

arXiv2020

Quantum-inspired terahertz spectroscopy with visible photons

Terahertz spectroscopy allows for identifying different isomers of materials, for drug discrimination as well as for detecting hazardous substances. As many dielectric materials used for packaging are transparent in the terahertz spectral range, substances might even be identified if packaged. Despite these useful applications, terahertz spectroscopy suffers from the still technically demanding detection of terahertz radiation. Thus, either coherent time-domain-spectroscopy schemes employing ultrafast pulsed lasers or continuous-wave detection with photomixers requiring two laser systems are used to circumvent the challenge to detect such low-energetic radiation without using cooled detectors. Here, we report on the first demonstration of terahertz spectroscopy, in which the sample interacts with terahertz idler photons, while only correlated visible signal photons are detected - a concept inspired by quantum optics. To generate these correlated signal-idler photon pairs, a periodically poled lithium niobate crystal and a 660 nm continuous-wave pump source are used. After propagating through a single-crystal nonlinear interferometer, the pump photons are separated from the signal radiation by highly efficient and narrowband volume Bragg gratings. An uncooled scientific CMOS camera detects the frequency-angular spectra of the remaining visible signal and reveals terahertz-spectral information in the Stokes as well as the anti-Stokes part of collinear forward generation. Neither cooled detectors nor expensive pulsed lasers for coherent detection are required. We demonstrate spectroscopy on the well-known absorption features in the terahertz spectral range of $α$-lactose monohydrate and para-aminobenzoic acid by detecting only visible photons.

physics.optics↗

arXiv2019

Terahertz Quantum Sensing

Quantum sensing is highly attractive for accessing spectral regions in which the detection of photons is technically challenging: sample information is gained in the spectral region of interest and transferred via entanglement into another spectral range, for which highly sensitive detectors are available. This is especially beneficial for terahertz radiation, as the corresponding photon energy lies in the range of a few meV - an energy where no semiconductor detectors are available and coherent detection schemes or cryogenically cooled bolometers have to be employed. Here, we report on the first demonstration of quantum sensing in the terahertz frequency range in which the terahertz photons interact with a sample in free space and information about the sample thickness is obtained by the detection of visible photons. A nonlinear single-crystal interferometer setup with a periodically poled lithium niobate crystal (PPLN) and a 660 nm pump source is used, generating visible (signal) photons and associated (idler) photons in the terahertz frequency range. Separation from the pump photons and detection of the visible signal photons is achieved by using highly efficient and narrowband volume Bragg gratings and an uncooled scientific complementary metal-oxide-semiconductor (sCMOS) camera. The acquired frequency-angular spectra show quantum interference in the Stokes as well as the Anti-Stokes part of collinear forward generation caused by spontaneous parametric down-conversion (SPDC) and down-conversion as well as up-conversion of thermal photons. The information encoded in the quantum interference can be used to determine the thickness of coatings or functional layers that are mainly transparent in the terahertz spectral range. As a first demonstration, we show layer thickness measurements with terahertz photons based on induced coherence without induced emission.

quant-ph↗