Coherent Raman microscopy, a rapid, chemical-specific, label-free imaging method, can be plagued by non-Raman background signals. Existing modulation schemes mitigate these but none remove all background signals. Here we demonstrate what we believe to be a novel scheme, chirp modulation stimulated Raman scattering (CM-SRS), based upon modulating uniquely the relative sign of the quadratic phase (linear chirp) of the input lasers. CM-SRS removes all non-Raman signals and is linear in both Raman oscillator strength and concentration. We demonstrate that CM-SRS is highly sensitive, quantitative, and background-free via imaging of traditionally challenging samples and the small molecule pharmacokinetics of single living cells.
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http://dx.doi.org/10.1364/OE.531274 | DOI Listing |
J Phys Chem A
December 2024
Departamento de Química Física y Química Inorgánica, Facultad de Ciencias─I.U. CINQUIMA, Paseo de Belén, 7, 47011 Valladolid, Spain.
The conformational space of 3-chloropropionic acid has been studied under the isolated conditions of a supersonic expansion using Stark-modulated free-jet absorption millimeter-wave and centimeter-wave chirped-pulse Fourier transform microwave spectroscopy techniques. The rotational spectra originating from the three most stable conformers including Cl and Cl isotopologues were observed in both experiments using helium expansion while a partial conformational relaxation involving skeletal rearrangements takes place in an argon expansion. The rotational parameters, geometries, and energy order were determined from the experiment, allowing a comparison with quantum chemical predictions.
View Article and Find Full Text PDFVital signs such as heart rate (HR) and respiration rate (RR) are essential physiological parameters that are routinely used to monitor human health and bodily functions. They can be continuously monitored through contact or contactless measurements performed in the home or a hospital. In this study, a contactless Doppler radar W-band sensing system was used for short-range, contactless vital sign estimation.
View Article and Find Full Text PDFInt J Mol Sci
December 2024
Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
Thyroid cancer is the most common endocrine malignancy in the United States, with an overall favorable prognosis. However, some patients experience poor outcomes due to the development of resistance to conventional therapies. Genetic alterations, including mutations in BRAF, Met, and p53, play critical roles in thyroid cancer progression, with the BRAF V600E mutation detected in over 60% of cases.
View Article and Find Full Text PDFWe present a spectroscopic method that employs a single linearly chirped laser pulse (LCLP) generated by external modulation to realize long-distance multi-point gas sensing. Even without frequency-chirping calibration, accurate single-shot spectral measurement is rendered possible by the high linearity of intrapulse chirping (linearity error of ∼10). Utilizing the LCLP's built-in capacity of time-division-multiplexing, high measurement sensitivity is guaranteed by introducing a multichannel intensity noise compensation mechanism.
View Article and Find Full Text PDFA chip-scaled single-soliton microcomb source promises wide applications in various fields. We demonstrate the deterministic single-soliton generation from both pump forward and backward tunings via sideband thermal compensation. The total soliton existing range (SER) is effectively expanded due to the thermal-lock effect and remains nearly the same regardless of the soliton states.
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