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JAAD Case Reports May 2024
PubMed: 38576901
DOI: 10.1016/j.jdcr.2023.08.027 -
Optics Express Mar 2024Terahertz (THz) continuous wave (CW) spectroscopy systems can offer extremely high spectral resolution over the THz band by photo-mixing high-performance...
Terahertz (THz) continuous wave (CW) spectroscopy systems can offer extremely high spectral resolution over the THz band by photo-mixing high-performance telecommunications-band (1530-1565 nm) lasers. However, typical THz CW detectors in these systems use narrow band-gap photoconductors, which require elaborate material growth and generate relatively large detector noise. Here we demonstrate that two-step photon absorption in a nano-structured low-temperature grown GaAs (LT-GaAs) metasurface which enables switching of photoconductivity within approximately one picosecond. We show that LT-GaAs can be used as an ultrafast photoconductor in CW THz detectors despite having a bandgap twice as large as the telecommunications laser photon energy. The metasurface design harnesses Mie modes in LT GaAs resonators, whereas metallic electrodes of THz detectors can be designed to support an additional photonic mode, which further increases photoconductivity at a desired wavelength.
PubMed: 38571206
DOI: 10.1364/OE.517422 -
Optics Express Mar 2024The thin flyer is a small-scale flying object, which is well known as the core functional element of the initiator. Understanding how flyers perform has been a...
The thin flyer is a small-scale flying object, which is well known as the core functional element of the initiator. Understanding how flyers perform has been a long-standing issue in detonator science. However, it remains a significant challenge to explore how the flyer is formed and functions in the barrel of the initiator via tabletop devices. In this study, we present dynamic and unprecedented images of flyer in barrel via high intensity short-pulse laser. Advanced radiography, coupled with a high-intensity picosecond laser X-ray source, has enabled the provision of state-of-the-art radiographs in a single-shot experiment for observing micron-scale flyer formation in a hollow cylinder in nanoseconds. The flyer was clearly visible in the barrel and was accelerated and restricted differently from that without the barrel. This first implementation of a tabletop X-ray source provided a new approach for capturing dynamic photographs of small-scale flying objects, which were previously reported to be accessible only via an X-ray phase-contrast imaging system at the advanced photon source. These efforts have led to a significant improvement of radiographic capability and a greater understanding of the mechanisms of "burst" of exploding foil initiators for this application.
PubMed: 38571190
DOI: 10.1364/OE.510930 -
Optics Express Mar 2024Terahertz (THz) microcavities have garnered considerable attention for their ability to localize and confine THz waves, allowing for strong coupling to remarkably...
Terahertz (THz) microcavities have garnered considerable attention for their ability to localize and confine THz waves, allowing for strong coupling to remarkably enhance the light-matter interaction. These properties hold great promise for advancing THz science and technology, particularly for high-speed integrated THz chips where transient interaction between THz waves and matter is critical. However, experimental study of these transient time-domain processes requires high temporal and spatial resolution since these processes, such as THz strong coupling, occur in several picoseconds and microns. Thus, most literature studies rarely cover temporal and spatial processes at the same time. In this work, we thoroughly investigate the transient cavity-cavity strong-coupling phenomena at THz frequency and find a Rabi-like oscillation in the microcavities, manifested by direct observation of a periodic energy exchange process via a phase-contrast time-resolved imaging system. Our explanation, based on the Jaynes-Cummings model, provides theoretical insight into this transient strong-coupling process. This work provides an opportunity to deeply understand the transient strong-coupling process between THz microcavities, which sheds light on the potential of THz microcavities for high-speed THz sensor and THz chip design.
PubMed: 38571106
DOI: 10.1364/OE.518799 -
Optics Express Mar 2024We demonstrate efficient anti reflection coatings based on adiabatic index matching obtained via nano-imprint lithography. They exhibit high total transmission,...
We demonstrate efficient anti reflection coatings based on adiabatic index matching obtained via nano-imprint lithography. They exhibit high total transmission, achromaticity (99.5% < T < 99.8% from 390 to 900 nm and 99% < T < 99.5% from 800 to 1600 nm) and wide angular acceptance (T > 99% up to 50 degrees). Our devices show high laser-induced damage thresholds in the sub-picosecond (>5 J/cm at 1030 nm, 500 fs), nanosecond (>150 J/cm at 1064 nm, 12 ns and >100 J/cm at 532 nm, 12 ns) regimes, and low absorption in the CW regime (<1.3 ppm at 1080 nm), close to those of the fused silica substrate.
PubMed: 38571103
DOI: 10.1364/OE.518828 -
Optics Express Mar 2024Non-line-of-sight (NLOS) imaging retrieves the hidden scenes by utilizing the signals indirectly reflected by the relay wall. Benefiting from the picosecond-level timing...
Non-line-of-sight (NLOS) imaging retrieves the hidden scenes by utilizing the signals indirectly reflected by the relay wall. Benefiting from the picosecond-level timing accuracy, time-correlated single photon counting (TCSPC) based NLOS imaging can achieve theoretical spatial resolutions up to millimeter level. However, in practical applications, the total temporal resolution (also known as total time jitter, TTJ) of most current TCSPC systems exceeds hundreds of picoseconds due to the combined effects of multiple electronic devices, which restricts the underlying spatial resolution of NLOS imaging. In this paper, an instrument response function deconvolution (IRF-DC) method is proposed to overcome the constraints of a TCSPC system's TTJ on the spatial resolution of NLOS imaging. Specifically, we model the transient measurements as Poisson convolution process with the normalized IRF as convolution kernel, and solve the inverse problem with iterative deconvolution algorithm, which significantly improves the spatial resolution of NLOS imaging after reconstruction. Numerical simulations show that the IRF-DC facilitates light-cone transform and frequency-wavenumber migration solver to achieve successful reconstruction even when the system's TTJ reaches 1200 ps, which is equivalent to what was previously possible when TTJ was about 200 ps. In addition, the IRF-DC produces satisfactory reconstruction outcomes when the signal-to-noise ratio (SNR) is low. Furthermore, the effectiveness of the proposed method has also been experimentally verified. The proposed IRF-DC method is highly applicable and efficient, which may promote the development of high-resolution NLOS imaging.
PubMed: 38571057
DOI: 10.1364/OE.518767 -
Optics Express Mar 2024The advent of optical metrology applications has necessitated the development of compact, reliable, and cost-effective picosecond lasers operating around 900 nm,...
The advent of optical metrology applications has necessitated the development of compact, reliable, and cost-effective picosecond lasers operating around 900 nm, specifically catering to the requirements of precise ranging. In response to this demand, our work introduces an innovative solution-an all-fiber, all-polarization-maintaining (PM) figure-9 mode-locked laser operating at 915 nm. The proposed figure-9 Nd-doped fiber laser has a 69.2 m long cavity length, strategically designed and optimized to yield pulses with a combination of high pulse energy and low repetition rate. The laser can generate 915 nm laser pulses with a pulse energy of 4.65 nJ, a pulse duration of 15.2 ps under the repetition rate of 3.05 MHz. The 1064 nm amplified spontaneous emission (ASE) is deliberately filtered out, in order to prevent parasitic lasing and increase the spectral proportion of the 915 nm laser. The all-PM fiber configuration of this laser imparts exceptional mode-locking performance and environmental robustness, which is confirmed by long-term output power and spectral stability test. This compact and long-term reliable fiber laser could be a promising light source for applications like inter-satellite ranging.
PubMed: 38570978
DOI: 10.1364/OE.519109 -
Optics Express Mar 2024We demonstrate what we believe to be a new approach to energetic picosecond 10.2-µm pulse generation based on nonlinear mixing of subnanosecond single-frequency 1338-nm...
We demonstrate what we believe to be a new approach to energetic picosecond 10.2-µm pulse generation based on nonlinear mixing of subnanosecond single-frequency 1338-nm pulses and broadband 1540-nm chirped pulses in a BGGSe crystal followed by a grating compressor for the purpose of seeding high-power CO amplifiers. The energy of the 10.2-µm pulses exceeding 60 µJ with 3.4%-rms fluctuation can be routinely obtained. Single-shot pulse duration measurement, performed by Kerr polarization rotation time-resolved by a streak camera, together with the pulse spectrum, indicates the pulse width is between 2.7-3 ps. Numerical calculations show that power broadening and dynamic gain saturation with Rabi-flopping can be induced with such an intense seed in a multi-atmospheric CO amplifier. These nonlinear effects greatly suppresses pulse splitting due to the comb-like spectrum of the CO molecule. A peak power exceeding 1 TW is expected after multipass of amplification while maintaining an appropriate high intensity by controlling the beam size along the path.
PubMed: 38570972
DOI: 10.1364/OE.517743 -
Journal of Oleo Science 2024Phospholipids and surfactants form membranes and other self-assembled structures in water. However, it is not fully understood how the surrounding water (hydration... (Review)
Review
Phospholipids and surfactants form membranes and other self-assembled structures in water. However, it is not fully understood how the surrounding water (hydration water) is involved in their structure formation. In this paper, I summarize the results of our investigation of the long-range hydration state of phospholipids and surfactants at their surfaces by means of terahertz spectroscopy. By observing the collective rotational dynamics of water in the picosecond time scale, this technique allows us to observe not only the water directly bound to the solute, but also the weakly affected water outside of it. For example, PC phospholipids inhibit water dynamics over long distances, whereas PE phospholipids make water more mobile than bulk water. The causes of this difference in hydration and how it is involved in the structural formation of the membrane are reviewed.
Topics: Lipoproteins; Phospholipids; Pulmonary Surfactants; Surface-Active Agents; Terahertz Spectroscopy; Water
PubMed: 38556277
DOI: 10.5650/jos.ess23188 -
International Journal of Molecular... Mar 2024While untargeted analysis of biological tissues with ambient mass spectrometry analysis probes has been widely reported in the literature, there are currently no... (Review)
Review
While untargeted analysis of biological tissues with ambient mass spectrometry analysis probes has been widely reported in the literature, there are currently no guidelines to standardize the workflows for the experimental design, creation, and validation of molecular models that are utilized in these methods to perform class predictions. By drawing parallels with hurdles that are faced in the field of food fraud detection with untargeted mass spectrometry, we provide a stepwise workflow for the creation, refinement, evaluation, and assessment of the robustness of molecular models, aimed at meaningful interpretation of mass spectrometry-based tissue classification results. We propose strategies to obtain a sufficient number of samples for the creation of molecular models and discuss the potential overfitting of data, emphasizing both the need for model validation using an independent cohort of test samples, as well as the use of a fully characterized feature-based approach that verifies the biological relevance of the features that are used to avoid false discoveries. We additionally highlight the need to treat molecular models as "dynamic" and "living" entities and to further refine them as new knowledge concerning disease pathways and classifier feature noise becomes apparent in large(r) population studies. Where appropriate, we have provided a discussion of the challenges that we faced in our development of a 10 s cancer classification method using picosecond infrared laser mass spectrometry (PIRL-MS) to facilitate clinical decision-making at the bedside.
Topics: Humans; Workflow; Mass Spectrometry
PubMed: 38542461
DOI: 10.3390/ijms25063491