Multiplexed photonic Doppler velocimetry systems are developed to measure velocities with high density in physics experiments such as shock physics experiments on novel materials. Decreasing the mesh size can lead to crosstalk issues, which can be overcome by wavelength multiplexing. Crosstalk has been characterized on a line of eight collimators with a pitch of 1 mm. A crosstalk-free photonic Doppler velocimetry system with 16 telecom wavelengths was built. Wavelength multiplexing provides as well a reduction in the total number of fiber components. The system was designed for velocities up to 1000 m/s and with a bandwidth of 2 GHz. In the frequency domain, the channel spacing is 100 GHz, which is more than enough to prevent any crosstalk. A ramp compression experiment was carried out by a high-pulsed-power generator to demonstrate the dynamic performances of the crosstalk free system at about 80 m/s.
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http://dx.doi.org/10.1063/5.0027331 | DOI Listing |
Proc Natl Acad Sci U S A
January 2025
Faculty of Technical Chemistry, Institute of Chemical Technologies and Analytics, Technische Universität Wien, Vienna 1060, Austria.
Atomic force microscopy-infrared spectroscopy (AFM-IR) is a photothermal scanning probe technique that combines nanoscale spatial resolution with the chemical analysis capability of mid-infrared spectroscopy. Using this hybrid technique, chemical identification down to the single molecule level has been demonstrated. However, the mechanism at the heart of AFM-IR, the transduction of local photothermal heating to cantilever deflection, is still not fully understood.
View Article and Find Full Text PDFWe demonstrate a (FMCW) light detection and ranging (LIDAR) system utilizing a (SNSPD) to measure vibrational spectra using reflected signals at the single-photon level. By determining the time-variant Doppler shift of the reflected probe signal, this system successfully reconstructs various audio signals, including pure sinusoidal, multi-tonal, and musical signals, up to 200 Hz, limited by the laser frequency modulation rate and the Nyquist sampling theorem. Additionally, we employ scanning galvo mirrors to perform 3D measurements and map audio signals from different regions in the scanned field of view.
View Article and Find Full Text PDFAnal Chem
January 2025
Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China.
Detection of trace gases, such as radioactive carbon dioxide, clumped isotopes, and reactive radicals, is of great interest and poses significant challenges in various fields. Achieving both high selectivity and high sensitivity is essential in this context. We present a highly selective molecular spectroscopy method based on comb-locked, mid-infrared, cavity-enhanced, two-photon absorption.
View Article and Find Full Text PDFSci Rep
December 2024
Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, 27599, USA.
A long-standing goal of neuroimaging is the non-invasive volumetric assessment of whole brain function and structure at high spatial and temporal resolutions. Functional ultrasound (fUS) and ultrasound localization microscopy (ULM) are rapidly emerging techniques that promise to bring advanced brain imaging and therapy to the clinic with the safety and low-cost advantages associated with ultrasound. fUS has been used to study cerebral hemodynamics at high temporal resolutions while ULM has been used to study cerebral microvascular structure at high spatial resolutions.
View Article and Find Full Text PDFPhotoacoustics
August 2024
Department of Physics, University of Auckland, Private Bag 92019, Auckland, 1010, New Zealand.
We present a technique called photoacoustic vector-flow (PAVF) to quantify the speed and direction of flowing optical absorbers at each pixel from acoustic-resolution PA images. By varying the receiving angle at each pixel in post-processing, we obtain multiple estimates of the phase difference between consecutive frames. These are used to solve the overdetermined photoacoustic Doppler equation with a least-squares approach to estimate a velocity vector at each pixel.
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