1,232 results match your criteria noise raman


Low-threshold 1150  nm single-polarization single-frequency Yb-doped DFB fiber laser.

Opt Lett 2021 Aug;46(15):3705-3708

We demonstrate a stable single-polarization single-frequency distributed feedback Bragg (DFB) fiber laser at 1150 nm based on a 5 cm long Yb-doped fiber which, to the best of our knowledge, is the first demonstration of a Yb-doped fiber-based single-frequency laser with a wavelength longer than 1120 nm. The threshold is as low as 10 mW. The measured maximum output power is 10. Read More

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Convolution Network with Custom Loss Function for the Denoising of Low SNR Raman Spectra.

Sensors (Basel) 2021 Jul 6;21(14). Epub 2021 Jul 6.

Department of Electronic Engineering, Maynooth University, W23 F2H6 Maynooth, County Kildare, Ireland.

Raman spectroscopy is a powerful diagnostic tool in biomedical science, whereby different disease groups can be classified based on subtle differences in the cell or tissue spectra. A key component in the classification of Raman spectra is the application of multi-variate statistical models. However, Raman scattering is a weak process, resulting in a trade-off between acquisition times and signal-to-noise ratios, which has limited its more widespread adoption as a clinical tool. Read More

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Label-free detection of brain tumors in a 9L gliosarcoma rat model using stimulated Raman scattering-spectroscopic optical coherence tomography.

J Biomed Opt 2021 Jul;26(7)

Georgia Institute of Technology & Emory Univ. School of Medicine, United States.

Significance: In neurosurgery, it is essential to differentiate between tumor and healthy brain regions to maximize tumor resection while minimizing damage to vital healthy brain tissue. However, conventional intraoperative imaging tools used to guide neurosurgery are often unable to distinguish tumor margins, particularly in infiltrative tumor regions and low-grade gliomas.

Aim: The aim of this work is to assess the feasibility of a label-free molecular imaging tool called stimulated Raman scattering-spectroscopic optical coherence tomography (SRS-SOCT) to differentiate between healthy brain tissue and tumor based on (1) structural biomarkers derived from the decay rate of signals as a function of depth and (2) molecular biomarkers based on relative differences in lipid and protein composition extracted from the SRS signals. Read More

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A simple method to generate arbitrary laser shapes for stimulated Raman adiabatic passage.

Rev Sci Instrum 2021 Jun;92(6):063206

College of Intelligence Science and Technology, National University of Defense Technology, Changsha, Hunan 410073, China.

Stimulated Raman adiabatic passage (STIRAP) is an effective technique to transfer state coherently with the features of both high fidelity and robustness in the field of quantum information and quantum precise measurement. In this note, we present a simple method to generate arbitrary laser shapes for STIRAP by controlling the modulation depth of the electro-optic modulator (EOM) and the diffraction efficiency of the acoustic-optic modulator (AOM) simultaneously. The EOM and AOM are used to control the power ratio between the two Raman lasers (pumping laser and Stokes laser) and the total power, respectively. Read More

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Application of Laser-Induced, Deep UV Raman Spectroscopy and Artificial Intelligence in Real-Time Environmental Monitoring-Solutions and First Results.

Sensors (Basel) 2021 Jun 5;21(11). Epub 2021 Jun 5.

Department of Engineering Geology and Hydrogeology, RWTH Aachen University, Lochnerstr. 4-20, 52064 Aachen, Germany.

Environmental monitoring of aquatic systems is the key requirement for sustainable environmental protection and future drinking water supply. The quality of water resources depends on the effectiveness of water treatment plants to reduce chemical pollutants, such as nitrates, pharmaceuticals, or microplastics. Changes in water quality can vary rapidly and must be monitored in real-time, enabling immediate action. Read More

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Single cell detection using intracellularly-grown-Au-nanoparticle based surface-enhanced Raman scattering spectroscopy for nasopharyngeal cell line classification.

Anal Methods 2021 Jul 23;13(28):3147-3153. Epub 2021 Jun 23.

College of Integrated Traditional Chinese and Western Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, China.

The aim of this study was to evaluate the feasibility of applying intracellularly-grown-Au-nanoparticle (IGAuNP)-based surface-enhanced Raman scattering (SERS) technology to classify two types of nasopharyngeal cancer (NPC) cell lines (CNE2 and CNE1). The IGAuNP technology provides excellent delivery efficiency of Au NPs to the cytoplasm and nucleus, thus leading to an extraordinary enhancement of the Raman signals of cells. Compared with normal Raman scattering (NRS) spectra of cells, IGAuNP-based SERS spectra not only have a high signal-to-noise ratio, but also can detect more characteristic Raman peaks, which can be used to explore more differences when comparing the biochemical components of different nasopharyngeal carcinoma cell lines. Read More

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Converting noise into solitons: optical self-organization through intermodal nonlinearity.

Opt Express 2021 Jun;29(12):18315-18324

We experimentally demonstrate a pump-pulse-induced conversion of noise into solitons in multimode optical fibers. The process is based on the recently discovered phenomenon of soliton self-mode conversion, where a pump soliton in a higher-order spatial mode crafts another well-defined soliton, originating purely from noise, in a lower-order mode at a longer wavelength through intermodal Raman scattering. The lack of the need for any seed or cavity feedback demonstrates that soliton self-mode conversion is a fundamentally unavoidable, but nevertheless tailorable and hence useful, self-organizing nonlinear optical effect capable of turning noise into transform limited solitons. Read More

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Optical design for laser tweezers Raman spectroscopy setups for increased sensitivity and flexible spatial detection.

Appl Opt 2021 Jun;60(16):4519-4523

We demonstrate a method to double the collection efficiency in laser tweezers Raman spectroscopy (LTRS) by collecting both the forward-scattered and backscattered light in a single-shot multitrack measurement. Our method can collect signals at different sample volumes, granting both the pinpoint spatial selectivity of confocal Raman spectroscopy and the bulk sensitivity of non-confocal Raman spectroscopy simultaneously. Further, we display that our approach allows for reduced detector integration time and laser power. Read More

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Multiplicative noise can induce a velocity change of propagating dissipative solitons.

Phys Rev E 2021 May;103(5):L050201

Department of Physics, University of Bayreuth, 95440 Bayreuth, Germany.

We investigate the influence of spatially homogeneous multiplicative noise on propagating dissipative solitons (DSs) of the cubic complex Ginzburg-Landau equation stabilized by nonlinear gradient terms. Here we focus on the nonlinear gradient terms, in particular on the influence of the Raman term and the delayed nonlinear gain. We show that a fairly small amount of multiplicative noise can lead to a change in the mean velocity for such systems. Read More

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Chemometrics-Assisted Raman Spectroscopy Characterization of Tunable Polymer-Peptide Hybrids for Dental Tissue Repair.

Front Mater 2021 May 10;8. Epub 2021 May 10.

Institute for Bioengineering Research, University of Kansas, Lawrence, KS, United States.

The interfaces that biological tissues form with biomaterials are invariably defective and frequently the location where failure initiates. Characterizing the phenomena that lead to failure is confounded by several factors including heterogeneous material/tissue interfaces. To seamlessly analyze across these diverse structures presents a wealth of analytical challenges. Read More

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Developing a Peak Extraction and Retention (PEER) Algorithm for Improving the Temporal Resolution of Raman Spectroscopy.

Anal Chem 2021 06 10;93(24):8408-8413. Epub 2021 Jun 10.

State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, China.

In spectroscopic analysis, push-to-the-limit sensitivity is one of the important topics, particularly when facing the qualitative and quantitative analyses of the trace target. Normally, the effective recognition and extraction of weak signals are the first key steps, for which there has been considerable effort in developing various denoising algorithms for decades. Nevertheless, the lower the signal-to-noise ratio (SNR), the greater the deviation of the peak height and shape during the denoising process. Read More

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Quantum-enhanced nonlinear microscopy.

Nature 2021 06 9;594(7862):201-206. Epub 2021 Jun 9.

ARC Centre of Excellence for Engineered Quantum Systems, University of Queensland, St Lucia, Queensland, Australia.

The performance of light microscopes is limited by the stochastic nature of light, which exists in discrete packets of energy known as photons. Randomness in the times that photons are detected introduces shot noise, which fundamentally constrains sensitivity, resolution and speed. Although the long-established solution to this problem is to increase the intensity of the illumination light, this is not always possible when investigating living systems, because bright lasers can severely disturb biological processes. Read More

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Dataset on capability of suppressing background noise and anti-tilting of divided-aperture differential confocal Raman microscopy system.

Data Brief 2021 Jun 11;36:107132. Epub 2021 May 11.

Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology, School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China.

The dataset describes the mechanism of suppressing the background noise of the divided-aperture differential confocal Raman microscopy system and the range of tilting angles that the system can handle. On the basis of the confocal microscopy (CM), the divided-aperture confocal microscopy divided the pupil plane of the objective lens into the illumination pupil and collection pupil. Compared with the CM, the divided-aperture confocal microscopy only changes the pupil parameters, according to the partially coherent imaging theory, we simulate and analyze the axial response curves of the divided-aperture confocal system and the traditional confocal system. Read More

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Hollow-core fiber photothermal methane sensor with temperature compensation.

Opt Lett 2021 Jun;46(11):2762-2765

We demonstrate a high sensitivity all-fiber spectroscopic methane sensor based on photothermal interferometry. With a 2.4-m-long anti-resonant hollow-core fiber, a 1654 nm distributed feedback laser, and a Raman fiber amplifier, a noise-equivalent concentration of ${\sim}{4. Read More

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Microsecond fingerprint stimulated Raman spectroscopic imaging by ultrafast tuning and spatial-spectral learning.

Nat Commun 2021 05 24;12(1):3052. Epub 2021 May 24.

Department of Biomedical Engineering, Boston University, Boston, MA, USA.

Label-free vibrational imaging by stimulated Raman scattering (SRS) provides unprecedented insight into real-time chemical distributions. Specifically, SRS in the fingerprint region (400-1800 cm) can resolve multiple chemicals in a complex bio-environment. However, due to the intrinsic weak Raman cross-sections and the lack of ultrafast spectral acquisition schemes with high spectral fidelity, SRS in the fingerprint region is not viable for studying living cells or large-scale tissue samples. Read More

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Fast denoising and lossless spectrum extraction in stimulated Raman scattering microscopy.

J Biophotonics 2021 May 16:e202100080. Epub 2021 May 16.

Key Laboratory of Optoelectronic Devices and Systems of Guangdong Province and Ministry of Education, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, China.

Stimulated Raman scattering (SRS) microscopy is a nonlinear optical imaging method for visualizing chemical content based on molecular vibrational bonds. However, the imaging speed and sensitivity are currently limited by the noise of the light beam probing the Raman process. In this paper, we present a fast non-average denoising and high-precision Raman shift extraction method, based on a self-reinforcing signal-to-noise ratio (SNR) enhancement algorithm, for SRS spectroscopy and microscopy. Read More

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Comparison of functional and discrete data analysis regimes for Raman spectra.

Anal Bioanal Chem 2021 May 15. Epub 2021 May 15.

Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743, Jena, Germany.

Raman spectral data are best described by mathematical functions; however, due to the spectroscopic measurement setup, only discrete points of these functions are measured. Therefore, we investigated the Raman spectral data for the first time in the functional framework. First, we approximated the Raman spectra by using B-spline basis functions. Read More

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Spectral and RIN properties of a single-frequency Raman fiber amplifier co-pumped by ASE source.

Opt Express 2021 May;29(10):15764-15771

Spectral and relative intensity noise (RIN) characteristics of a single-frequency Raman fiber amplifier co-pumped by amplified spontaneous emission (ASE) sources are investigated experimentally. Due to the relatively lower intensity noise of ASE sources compared to usual fiber laser pumps, the full width at half maximum (FWHM) linewidth of the signal laser increases negligibly. But there is significant increase in RIN and spectral wings due to the noise transfer at high frequency from the ASE source during the Raman amplification. Read More

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Continuous-variable quantum key distribution coexisting with classical signals on few-mode fiber.

Opt Express 2021 May;29(10):14486-14504

Continuous-variable quantum key distribution (CVQKD) holds an advantage of well compatibility with classical coherent optical communications. However, there exists a performance trade-off between CVQKD and classical communication on single-mode fiber (SMF) because of the spontaneous Raman scattering. Space-division multiplexing (SDM) technique may provide a feasible way to mitigate this performance trade-off in short-distance communication while CVQKD coexisting with classical signals on few-mode fiber (FMF). Read More

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Generation of coherent multicolor noise-like pulse complex in Yb-doped fiber laser mode-locked by GIMF-SA.

Opt Express 2021 May;29(10):14336-14344

We have demonstrated the generation of multicolor noise-like pulse complex in a passively Yb-doped mode-locked fiber laser based on a single mode-graded index multimode-single mode fiber (SMF-GIMF-SMF) device as the saturable absorber (SA). The stimulated Raman scattering (SRS) effect leads to the cascaded generation of the main noise-like pulse (NLP) at 1028.8 nm together with the noise like Raman pulse (RP) at 1076. Read More

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2.4  kW 1045  nm narrow-spectral-width monolithic single-mode CW fiber laser by using an FBG-based MOPA configuration.

Appl Opt 2021 May;60(13):3740-3746

A 24 kW narrow-spectral-width near-diffraction-limited monolithic fiber laser system at ${\sim}{1045.2}\;{\rm{nm}}$ in a fiber Bragg grating (FBG)-based master oscillator power amplifier (MOPA) configuration is demonstrated in this paper. The near-diffraction-limited beam quality (${{\rm{M}}^2}\sim{1. Read More

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Combining vancomycin-modified gold nanorod arrays and colloidal nanoparticles as a sandwich model for the discrimination of Gram-positive bacteria and their detection via surface-enhanced Raman spectroscopy (SERS).

Analyst 2021 Jun 4;146(11):3642-3653. Epub 2021 May 4.

East Anatolia High Technology Application and Research Center (DAYTAM), Ataturk University, 25240 Erzurum, Turkey. and Department of Chemical Engineering, Ataturk University, 25240 Erzurum, Turkey and Department of Nanoscience and Nanoengineering, Ataturk University, 25240 Erzurum, Turkey.

This study reports the development of a highly sensitive antibiotic-based discrimination and sensor platform for the detection of Gram-positive bacteria through surface-enhanced Raman spectroscopy (SERS). Herein, a combination of gold nanorod arrays (GNAs) and colloidal gold nanoparticles (AuNPs) was used as a SERS platform. To specifically capture Gram-positive bacteria, both GNAs and AuNPs were functionalized with thiol-modified vancomycin (HS-Van) molecules. Read More

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Frequency Shift Surface-Enhanced Raman Spectroscopy Sensing: An Ultrasensitive Multiplex Assay for Biomarkers in Human Health.

ACS Sens 2021 05 3;6(5):1704-1716. Epub 2021 May 3.

CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, the Chinese Academy of Sciences, Beijing 100049, China.

The sensitive and selective detection of biomarkers for human health remains one of the grand challenges of the analytical sciences. Compared to established methods (colorimetric, (chemi) luminescent), surface-enhanced Raman spectroscopy (SERS) is an emerging alternative with enormous potential for ultrasensitive biological detection. Indeed even attomolar (10 M) detection limits are possible for SERS due to an orders-of-magnitude boosting of Raman signals at the surface of metallic nanostructures by surface plasmons. Read More

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Metal-enhanced sensing platform for the highly sensitive detection of C-reactive protein antibody and rhodamine B with applications in cardiovascular diseases and food safety.

Dalton Trans 2021 May 30;50(20):6962-6974. Epub 2021 Apr 30.

Faculty of Materials Science and Technology, University of Science, Ho Chi Minh City, Viet Nam.

The potential applications of metal-enhanced fluorescence (MEF) devices include biosensors for the detection of trace amounts in biosciences, biotechnology, and pathogens that are relevant to medical diagnostics and food control. In the present study, the silver (Ag) film thickness (56 nm) of an MEF system was calibrated to maximize the depth-to-width ratio (Γ) of the surface plasmon resonance (SPR) active metal from reflectance dip curves. Upon plasmon coupling with thermally evaporated Ag, we demonstrated a 2. Read More

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Fiber laser technologies for photoacoustic microscopy.

Vis Comput Ind Biomed Art 2021 Apr 30;4(1):11. Epub 2021 Apr 30.

Guangdong Provincial Key Laboratory of Fiber Optic Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou, 510632, China.

Fiber laser technology has experienced a rapid growth over the past decade owing to increased applications in precision measurement and optical testing, medical care, and industrial applications, including laser welding, cleaning, and manufacturing. A fiber laser can output laser pulses with high energy, a high repetition rate, a controllable wavelength, low noise, and good beam quality, making it applicable in photoacoustic imaging. Herein, recent developments in fiber-laser-based photoacoustic microscopy (PAM) are reviewed. Read More

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Recognition of chronic renal failure based on Raman spectroscopy and convolutional neural network.

Photodiagnosis Photodyn Ther 2021 Jun 26;34:102313. Epub 2021 Apr 26.

College of Software, Xinjiang University, Urumqi, 830046, Xinjiang, China; Key Laboratory of Signal Detection and Processing, Xinjiang University, Urumqi, 830046, Xinjiang, China.

Purpose: Chronic renal failure (CRF) is a disease with a high morbidity rate that can develop into uraemia, resulting in a series of complications, such as dyspnoea, mental disorders, hypertension, and heart failure. CRF may be controlled clinically by drug intervention. Therefore, early diagnosis and control of the disease are of great significance for the treatment and prevention of chronic renal failure. Read More

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Hybrid Raman-erbium random fiber laser with a half open cavity assisted by artificially controlled backscattering fiber reflectors.

Sci Rep 2021 Apr 28;11(1):9169. Epub 2021 Apr 28.

Department of Electrical Electronic and Communication Engineering, Public University of Navarra, 31006, Pamplona, Spain.

A hybrid Raman-erbium random fiber laser with a half-open cavity assisted by chirped artificially controlled backscattering fiber reflectors is presented. A combination of a 2.4 km-long dispersion compensating fiber with two highly erbium-doped fiber pieces of 5 m length were used as gain media. Read More

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Super-resolution vibrational microscopy by stimulated Raman excited fluorescence.

Light Sci Appl 2021 Apr 20;10(1):87. Epub 2021 Apr 20.

Department of Chemistry, Columbia University, New York, NY, 10027, USA.

Inspired by the revolutionary impact of super-resolution fluorescence microscopy, super-resolution Raman imaging has been long pursued because of its much higher chemical specificity than the fluorescence counterpart. However, vibrational contrasts are intrinsically less sensitive compared with fluorescence, resulting in only mild resolution enhancement beyond the diffraction limit even with strong laser excitation power. As such, it is still a great challenge to achieve biocompatible super-resolution vibrational imaging in the optical far-field. Read More

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The Scattered Light Time-history Diagnostic suite at the National Ignition Facility.

Rev Sci Instrum 2021 Mar;92(3):033511

Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA.

The Scattered Light Time-history Diagnostic (SLTD) is being implemented at the National Ignition Facility (NIF) to greatly expand the angular coverage of absolute scattered-light measurements for direct- and indirect-drive inertial confinement fusion (ICF) experiments. The SLTD array will ultimately consist of 15 units mounted at a variety of polar and azimuthal angles on the NIF target chamber, complementing the existing NIF backscatter suite. Each SLTD unit collects and diffuses scattered light onto a set of three optical fibers, which transport the light to filtered photodiodes to measure scattered light in different wavelength bands: stimulated Brillouin scattering (350 nm-352 nm), stimulated Raman scattering (430 nm-760 nm), and ω/2 (695 nm-745 nm). Read More

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Measuring the phase noise of Raman lasers with an atom-based method.

Rev Sci Instrum 2021 Mar;92(3):033203

College of Artificial Intelligence, National University of Defense Technology, Changsha, Hunan 410073, China and Interdisciplinary Center for Quantum Information, National University of Defense Technology, Changsha, Hunan 410073, China.

Phase noise of Raman lasers is a major source of noise for a Raman-type cold atom interferometer, which is traditionally measured using the signal source analyzer. We report here an atom-based method to measure the phase noise performance between two Raman lasers. By analyzing and calibrating the system noise sources, we can characterize the contribution of phase noise from the total deviation of the relative atom population at the middle of the interference fringe. Read More

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