Search Results (33)

Coherent Raman scattering (CRS) techniques such as coherent anti-Stokes Raman scattering (CARS) provide chemically specific vibrational contrast with signal levels far exceeding spontaneous Raman scattering (SpRS). Extending these to broadband excitation enables multiplex detection across wide spectral regions, including the fingerprint region, CH-stretch bands and high-frequency vibrational modes. This review provides a structured overview of excitation architecture for broadband CRS, ranging from low-energy oscillator schemes to energy-scalable platforms. The discussion is organized along key design parameters, including spectral bandwidth, excitation intensity, and probe delay, which jointly determine the accessible operating regimes. Rather than representing competing methods, the reviewed architectures are presented as a complementary toolbox for application-driven spectroscopy in chemically reactive environments and complex biological systems. In addition, a representative OPCPA-based implementation is presented as a platform demonstration to illustrate accessible operating regimes, single-shot stability, and multiplex detection capability under realistic experimental conditions. Full article

Label-free imaging is becoming ever more important, especially in modern molecular biophysics. This method allows observation of biological structures and dynamics without the alteration caused by dyes or genetic labels. Coherent Anti-Stokes Raman Scattering (CARS) microscopy represents a unique method that utilizes the intrinsic vibrational signatures of biomolecules, thereby transforming the field. Fluorescence-based methods show marked sensitivity, but may cause photobleaching, labeling artifacts, and inadequate biochemical detection. CARS enables chemically specific, real-time imaging of molecular structures, e.g., lipids, proteins and nucleic acids, within their natural environment. Over the past decade, advances in laser technology, detection methods, and computer analysis have turned CARS from a rare optical phenomenon into a useful tool applied in many fields, from basic research on molecular structure to practical biomedical imaging. This review presents the principles of CARS microscopy and the latest achievements in this field, highlighting its impact on molecular and cellular biophysics, as well as exploring the potential of artificial intelligence and multimodal approaches to increase its applications in precision medicine. In this context, CARS serves both a state-of-the-art imaging technique and a means of transforming internal molecular vibrations into information useful in biology and biophysics. In this way, it combines the physical sciences with molecular biology, enabling innovative biomedical research. Full article

With the rapid advancement of biology and life sciences, there is an increasing demand for observing sub-cellular structures and molecular interactions at submicroscopic or even single-molecule levels, providing critical insights into life activities and disease diagnostics. Raman spectroscopy, which relies on molecular vibrational energy transitions, enables non-label and non-invasive cellular visualization, holding significant potential for modern medical technology. The microscopy method based on the coherent anti-Stokes Raman scattering effect, a novel visualization modality with superior signal intensity, chemical specificity, and label-free capability, demonstrates great promise in biomedical applications. Recently, dual-comb technology, consisting of two frequency combs with slightly different repetition rates, as a powerful light source has been successfully applied in CARS applications with the excellent performance characteristics of rapid acquisition, high resolution, and high signal-to-noise ratio. The dual-comb technique allows to clearly resolve sharp molecular lines and could suppress the non-resonant background in CARS. Through recent research progress, this work reviews the generation of dual-comb lasers based on a single cavity, the development of dual-comb CARS systems, and their biomedical applications. This review could provide further insights into high-resolution dual-comb CARS and potential ways to design such technology for potential biomedical applications. Full article

Multimodal imaging techniques have the potential to enhance the interpretation of histology by offering additional molecular and structural information beyond that accessible through hematoxylin and eosin (H&E) staining alone. Here, we present a quantitative approach for comparing the information content of different image modalities, such as H&E and multimodal imaging. We used a combination of deep learning and radiomics-based feature extraction with different information markers, implemented in Python 3.12, to compare the information content of the H&E stain, multimodal imaging, and the combined dataset. We also compared the information content of individual channels in the multimodal image and of different Coherent Anti-Stokes Raman Scattering (CARS) microscopy spectral channels. The quantitative measurements of information that we utilized were Shannon entropy, inverse area under the curve (1-AUC), the number of principal components describing 95% of the variance (PC95), and inverse power law fitting. For example, the combined dataset achieved an entropy value of 0.5740, compared to 0.5310 for H&E and 0.5385 for the multimodal dataset using MobileNetV2 features. The number of principal components required to explain 95 percent of the variance was also highest for the combined dataset, with 62 components, compared to 33 for H&E and 47 for the multimodal dataset. These measurements consistently showed that the combined datasets provide more information. These observations highlight the potential of multimodal combinations to enhance image-based analyses and provide a reproducible framework for comparing imaging approaches in digital pathology and biomedical image analysis. Full article

Tan spot disease, caused by Pyrenophora tritici-repentis, poses a significant threat to wheat production worldwide. Early detection and precise fungicide application are essential for effective disease management. This study explores the potential of Raman spectroscopy—specifically surface-enhanced Raman spectroscopy (SERS) and coherent anti-Stokes Raman scattering (CARS)—as non-invasive tools for identifying fungal infection and assessing wheat’s biochemical response to propiconazole treatment. The methodology is entirely theoretical; no laboratory experiments were conducted. Instead, all spectral graphs and figures were generated through a collaborative process between the author and Microsoft Copilot, which served as a rendering tool. These AI-assisted visualizations simulate Raman responses based on known molecular interactions and literature data. The results demonstrate the conceptual feasibility of Raman-based diagnostics for precision agriculture, offering a sustainable approach to disease monitoring and fungicide management. Full article

The development and characterization of a sustainable carboxymethylcellulose (CMC)-based material hosting Egyptian blue (EB) as a luminophore with emission in both the visible and NIR regions is herein presented and discussed, demonstrating its potential to be applied in a variety of applications, such as bioimaging, sensing, and security marking. Solution casting was used to synthesize the films, with citric acid (CA) as a crosslinking agent. Fully characterization was performed using attenuated total reflection (ATR) and coherent anti-Stokes Raman scattering (CARS) spectroscopy, zeta potential, UV–Vis, and photoluminescence (PL) spectroscopy, and thermal analysis techniques, such as thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results confirm the effective crosslinking of CMC with CA within CMC–EB–CA films with 1.5 and 3% of EB. The introduction of EB retained its usual NIR emission with λ_em max = ~950 nm reaching quantum yield values in the range of 11.2–12.8% while also enabling a stable dispersion within the CMC matrix, as confirmed using CARS imaging and zeta potential. Additionally, the CMC films exhibited the characteristic clustering-triggered emission (CTE) in the blue region at 430 nm with a slight increase in luminescence quantum yield (Φ) from 5.8 to 6.1% after crosslinking with citric acid. Full article

Coherent anti-Stokes Raman scattering (CARS) is a powerful nonlinear spectroscopic technique widely used in biological imaging, chemical analysis, and combustion and flame diagnostics. The adoption of pulse shapers in CARS has emerged as a useful approach, offering precise control of optical waveforms. By tailoring the phase, amplitude, and polarization of laser pulses, the pulse shaping approach enables selective excitation, spectral resolution improvement, and non-resonant background suppression in CARS. This paper presents a comprehensive review of applying pulse shaping techniques in CARS spectroscopy for biophotonics. There are two different pulse shaping strategies: passive pulse shaping and active pulse shaping. Two passive pulse shaping techniques, hybrid CARS and spectral focusing CARS, are reviewed. Active pulse shaping using a programmable pulse shaper such as spatial light modulator (SLM) is discussed for CARS spectroscopy. Combining active pulse shaping and passive shaping, optimizing CARS with acousto-optic programmable dispersive filters (AOPDFs) is discussed and illustrated with experimental examples conducted in the authors’ laboratory. These results underscore pulse shapers in advancing CARS technology, enabling improved sensitivity, specificity, and broader applications across diverse scientific fields. Full article

This paper presents an overview of the application of Raman spectroscopy (RS) in characterizing carotenoids, which have recently gained attention due to new findings on their health-promoting effects and rising demand in the food, pharmaceutical, and cosmetic industries. The backbone structure in the form of a polyene chain makes carotenoids sensitive to Raman spectroscopy, mainly due to the stretching vibrations of their conjugated double bonds. Raman spectroscopy is increasingly used in agricultural and food sciences and technologies as it is a non-preparative, environmentally friendly, fast and efficient method for characterizing target analytes. The application of RS in the qualitative and quantitative analysis of carotenoids requires the careful selection and adjustment of various instrument parameters (e.g., laser wavelength, laser power, spectral resolution, detector type, etc.) as well as performing complex chemometric modeling to interpret the Raman spectra. Most of the studies covered in this review focus more on qualitative than quantitative analysis. The most frequently used laser wavelengths are 1064, 785, and 532 nm, while 633 nm is the least used. Considering the sensitivity and complexity of RS, the present study focuses on the specific and critical points in the analysis of carotenoids by RS. The main methodological and experimental principles in the study of food carotenoids by RS are discussed and best practices recommended, while the future prospects and expectations for a wider application of RS, especially in food quality assessment, are emphasized. New Raman techniques such as Spatially Offset Raman Spectroscopy (SORS), Coherent Anti-Stokes Raman Spectroscopy (CARS) and Stimulated Raman Scattering Spectroscopy (SRS), as well as the application of artificial intelligence, are also described in the context of carotenoids analysis. Full article

Dupuytren’s disease (DD) is a prevalent fibroproliferative disorder of the hand, shaped by genetic, epigenetic, and environmental influences. The extracellular matrix (ECM) is a complex assembly of diverse macromolecules. Alterations in the ECM’s content, structure and organization can impact both normal physiological functions and pathological conditions. This study explored the content and organization of glycosaminoglycans, proteoglycans, and collagen in the ECM of patients at various stages of DD, assessing their potential as prognostic indicators. This research reveals, for the first time, relevant changes in the complexity of chondroitin/dermatan sulfate structures, specifically an increase of disaccharides containing iduronic acid residues covalently linked to either N-acetylgalactosamine 6-O-sulfated or N-acetylgalactosamine 4-O-sulfated, correlating with the disease’s severity. Additionally, we noted an increase in versican expression, a high molecular weight proteoglycan, across stages I to IV, while decorin, a small leucine-rich proteoglycan, significantly diminishes as DD progresses, both confirmed by mRNA analysis and protein detection via confocal microscopy. Coherent anti-Stokes Raman scattering (CARS) microscopy further demonstrated that collagen fibril architecture in DD varies importantly with disease stages. Moreover, the urinary excretion of both hyaluronic and sulfated glycosaminoglycans markedly decreased among DD patients.Our findings indicate that specific proteoglycans with galactosaminoglycan chains and collagen arrangements could serve as biomarkers for DD progression. The reduction in glycosaminoglycan excretion suggests a systemic manifestation of the disease. Full article

The combustion process is complex and harsh, and the supersonic combustion flow field is also characterized by short duration and supersonic speed, which makes the real-time diagnostic technology for the transient environment extremely demanding. It is of great significance to realize high time-resolved accurate measurement of temperature, component concentration, and other parametric information of the combustion field to study the transient chemical reaction dynamics of the combustion field. Femtosecond CARS spectroscopy can effectively avoid the collision effect between particles in the measurement process and reduce the influence of the non-resonant background to improve the measurement accuracy and realize the time-resolved measurement on a millisecond scale. This paper introduces the development history of femtosecond CARS spectroscopy, points out its advantages and disadvantages, and looks forward to the future development trend to carry out high time-resolved measurements, establish a database of temperature changes in various complex combustion fields, and provide support for the study of engine mechanisms. Full article

Despite their relatively low incidence globally, central nervous system (CNS) tumors remain amongst the most lethal cancers, with only a few other malignancies surpassing them in 5-year mortality rates. Treatment decisions for brain tumors heavily rely on histopathological analysis, particularly intraoperatively, to guide surgical interventions and optimize patient outcomes. Frozen sectioning has emerged as a vital intraoperative technique, allowing for highly accurate, rapid analysis of tissue samples, although it poses challenges regarding interpretive errors and tissue distortion. Raman histology, based on Raman spectroscopy, has shown great promise in providing label-free, molecular information for accurate intraoperative diagnosis, aiding in tumor resection and the identification of neurodegenerative disease. Techniques including Stimulated Raman Scattering (SRS), Coherent Anti-Stokes Raman Scattering (CARS), Surface-Enhanced Raman Scattering (SERS), and Tip-Enhanced Raman Scattering (TERS) have profoundly enhanced the speed and resolution of Raman imaging. Similarly, Confocal Laser Endomicroscopy (CLE) allows for real-time imaging and the rapid intraoperative histologic evaluation of specimens. While CLE is primarily utilized in gastrointestinal procedures, its application in neurosurgery is promising, particularly in the context of gliomas and meningiomas. This review focuses on discussing the immense progress in intraoperative histology within neurosurgery and provides insight into the impact of these advancements on enhancing patient outcomes. Full article

The influence of the interference between coherent processes in third-order nonlinear Raman scattering on the spectral shapes of Raman-scattered light waves is numerically modeled and discussed in the cases of commonly used coherent Raman spectroscopy techniques. The effects on the lineshapes depending on the laser intensity are analyzed for the coherent Raman spectroscopy performed via the excitation of molecular systems with focused laser pulses at high intensities. In this case, the interplay between the coherent processes in nonlinear Raman scattering, as well as laser power-induced resonance effects, may be significant and should be taken into account in the spectral lineshape analysis in coherent Raman spectroscopy and its related applications, since the coherent Raman spectra may be considerably modified. Full article

Simultaneous gas phase temperature and water vapor concentration measurement are important to understand reacting flows such as combustion or gas reforming processes. Here, coherent anti-Stokes Raman scattering (CARS) offers the possibility for non-intrusive measurements with a high temporal and spatial resolution. Therefore, this work demonstrates the simultaneous measurement of temperature and relative water vapor–nitrogen concentrations by using dual-pump vibrational coherent anti-Stokes Raman scattering (DPVCARS). A calibration procedure is developed for a temperature range of 473 K to 673 K and a water vapor concentration of 24% to 46% at ambient pressure. This setup is tested with 500 CARS single pulse spectra taken in a gas cell at a known temperature and concentration. Based on these results, information about precision and accuracy can be delivered. Full article

Information on the penetration depth, pathways, metabolization, storage of vehicles, active pharmaceutical ingredients (APIs), and functional cosmetic ingredients (FCIs) of topically applied formulations or contaminants (substances) in skin is of great importance for understanding their interaction with skin targets, treatment efficacy, and risk assessment—a challenging task in dermatology, cosmetology, and pharmacy. Non-invasive methods for the qualitative and quantitative visualization of substances in skin in vivo are favored and limited to optical imaging and spectroscopic methods such as fluorescence/reflectance confocal laser scanning microscopy (CLSM); two-photon tomography (2PT) combined with autofluorescence (2PT-AF), fluorescence lifetime imaging (2PT-FLIM), second-harmonic generation (SHG), coherent anti-Stokes Raman scattering (CARS), and reflectance confocal microscopy (2PT-RCM); three-photon tomography (3PT); confocal Raman micro-spectroscopy (CRM); surface-enhanced Raman scattering (SERS) micro-spectroscopy; stimulated Raman scattering (SRS) microscopy; and optical coherence tomography (OCT). This review summarizes the state of the art in the use of the CLSM, 2PT, 3PT, CRM, SERS, SRS, and OCT optical methods to study skin penetration in vivo non-invasively (302 references). The advantages, limitations, possibilities, and prospects of the reviewed optical methods are comprehensively discussed. The ex vivo studies discussed are potentially translatable into in vivo measurements. The requirements for the optical properties of substances to determine their penetration into skin by certain methods are highlighted. Full article

In view of the uncertainty in the calibration process of two-color plane laser-induced fluorescence (PLIF) temperature measurement, a new calibration method is proposed, in which the influence of fluorescence yield is considered. The calibration process was carried out at high and low temperature region, respectively. Then, the bias of thermometry results origin from quenching is restrained. This new calibration method is validated in a jet flame with temperature range of 1300–1800 K. Here, the temperature results from Coherent Anti-Stokes Raman scattering (CARS), single-point calibrated PLIF, and two-point calibrated PLIF are all acquired with the maximum standard errors of 13 K, 36 K, and 37 K, respectively. The temperature deviation between the average results from PLIF and Coherent Anti-Stokes Raman scattering (CARS) is 120 K and 10 K, when the two-point and one-point calibration methods are used. Therefore, the two-point calibrated PLIF is preferred in the combustion field, especially with a large temperature range and strong quenching coefficient. Full article