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220 W Raman fiber laser at 1.24 μm based on phosphosilicate fiber
摘要： A Raman fiber laser with more than 220 W output at 1.24 μm with phosphorus-doped single-mode fiber as gain medium is reported. The laser consists of a 30 m long piece of fiber and a pair of fiber Bragg gratings with different bandwidth, pumped with a high power 1064 nm Yb fiber laser. The optical conversion efficiency is 64% and the slope efficiency is 71.4%. The full width half-maximum linewidth at the maximum output is 5.6 nm. To the best of our knowledge, the reported power is an order magnitude higher than previous reports in phosphosilicate fiber Raman laser.
关键词： Raman laser,phosphosilicate fiber,Fiber laser
更新于2025-11-28 14:24:03
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Rectangular Pulse Generation from a Mode Locked Raman Fiber Laser
摘要： Rectangular and step-like pulses are generated in a mode locked Raman fiber laser with a nonlinear optical loop mirror. The Raman laser has a typical figure-8 configuration. Stable rectangular pulses with a fundamental repetition rate of 733 kHz are obtained. As the increasing of the pump power, the Raman pulse evolves to a step-like rectangular pulse. The maximum pulse energy is 64.1 nJ with a pulse width of 25.1 ns. After spectrally resolved measurements, the step-like pulse is proved to be induced by the dual wavelength oscillation. It is the first report of rectangular pulsed output in mode-locked Raman fiber laser to the best of our knowledge.
关键词： Laser mode locking,Raman scattering,Fiber lasers
更新于2025-11-28 14:24:03
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Diode-pumped single-pass tunable mid-infrared gas Raman source by methane-filled hollow-core fiber
摘要： We report here, to the best of our knowledge, the first diode-pumped single-pass tunable mid-infrared fiber gas Raman laser source using methane-filled hollow-core fibers. Pumped by a homemade tunable high peak-power amplified diode laser, whose wavelength covers the range of 1540 nm to 1560 nm, the mid-infrared laser emission over the range of 2796 nm to 2863 nm is generated by the stimulated Raman scattering of methane molecules. The highest average output power of ~34 mW at 2829 nm is achieved with 14.2 m fiber at 16 bar when pumped at 1550 nm. This paper opens new opportunities for compact tunable mid-infrared fiber lasers.
关键词： gas lasers,Raman lasers,fibre lasers,stimulated Raman scattering
更新于2025-11-28 14:23:57
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Novel combined instrumentation for laser-induced breakdown spectroscopy and Raman spectroscopy for the <i>in situ</i> atomic and molecular analysis of minerals
摘要： An instrument combining laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy was developed for the in situ atomic and molecular composition analysis of minerals. The apparatus consists of an optical system, a sample chamber, a spectrometer for Raman and another for LIBS, as well as a control system equipped with laboratory-written software. Gypsum, calcite, prehnite, pearl, lazurite, and several mixtures of NaBr and CaCO3 were selected as samples for evaluation of the performance of the instrument. Sulfate, carbonate, silicate, and crystalline water were identified and different structures of CaCO3 were clearly distinguished by the use of a Gaussian fit. The limit of detection for CaCO3 in a NaBr mixture was 5.7 mg/g by Raman. LIBS was employed to determine calcium, magnesium, iron, sodium, aluminum, and carbon with the newly developed system. The limits of detection obtained for Ca, Na, and C were 90.2 lg/g, 84.6 lg/g, and 2.5 mg/g, respectively. The experimental results from commercial Raman spectroscopy instruments were used to verify and support the measurements from this novel instrument.
关键词： Instrumentation,Raman spectroscopy,laser-induced breakdown spectroscopy (LIBS),mineral,LIBRAS
更新于2025-11-25 10:30:42
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Multifunctional and Recyclable TiO2 Hybrid Sponges for Efficient Sorption, Detection, and Photocatalytic Decomposition of Organic Pollutants
摘要： Developing techniques for monitoring and removing organic pollutants such as solvents and dyes in environmental media is a very important task nowadays. To get rid of the pollutants, efficient materials that can sorb, detect, and decompose such compounds have been consistently sought after. Herein, we demonstrate a simple and inexpensive method to fabricate eco-friendly multifunctional and recyclable TiO2 hybrid sponges composed of a polydimethylsiloxane (PDMS) network and functional nanoparticles. Water-soluble crystals were used to construct porous templates and TiO2 nanoparticles were additionally integrated into the templates where liquid PDMS was filled. After curing the PDMS, the TiO2 integrated hybrid sponges were finally obtained by dissolving the templates with water. By using the fabricated hybrid sponges, sorbed organic pollutants were qualitatively detected via molecular-specific Raman signals. Furthermore, we showed the recyclability by achieving photocatalytic decomposition of the sorbed pollutants induced by the TiO2 nanoparticles. These results are instructive for further applications and also contribute toward solving problems relating to environmental pollution.
关键词： TiO2 hybrid sponge,Raman detection,photocatalytic decomposition,organic pollutants,efficient sorption
更新于2025-11-25 10:30:42
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Efficiency and Quality Issues in the Production of Black Phosphorus by Mechanochemical Synthesis: A Multi-Technique Approach
摘要： Black phosphorus (BP) is a two-dimensional material potentially of great interest for applications in the fields of energy, sensing, and microelectronics. One of the most interesting methods to obtain BP is the conversion from red phosphorus (RP) by means of high-energy mechanochemical synthesis. To date, however, this synthesis process was not well characterized. In this work, starting from the mathematical model of energy transfer during the ball milling process, we investigate the effects on RP → BP conversion of three experimental parameters, the rotation speed, the milling time, and the weight ratio between the spheres and the milled material (BtPw ratio). The efficiency of the conversion process was verified by solid-state NMR, Raman spectroscopy, and X-ray diffraction. Whereas the first two parameters have a minor importance, the BtPw ratio plays a primary role in the RP → BP conversion. Yields approaching 100% can be obtained also with short milling times (15 min) and adequate rotation speed (e.g., 500 r.p.m.), provided that the BtPw ratio >40:1 is used. These results confirm the energy sustainability of the mechanochemical synthesis approach.
关键词： diffraction,solid-state NMR,anode,post-lithium ion batteries,Raman,mechanochemical synthesis
更新于2025-11-21 11:18:25
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Structural, optical and photoluminescence studies of sol-gel synthesized pure and iron doped TiO2 photocatalysts
摘要： Pure and Iron doped TiO2 nanoparticles were synthesized using the sol-gel method. These materials were characterized by X-ray diffractometer (XRD), high-resolution transmission electron microscope (HR-TEM), scanning electron microscope (SEM), Energy dispersive X-ray (EDX), UV-Vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared (FTIR), Raman and fluorescence spectrometer. XRD analysis revealed that all the samples were a single phase with anatase nanocrystallite structures. The crystallite size of titania reduced from 9.64 nm to 7 nm with Fe doping. The HRTEM images of the TiO2 and 3% Fe doped TiO2 have revealed that all the particles have a spherical shape with an average particle size of 10 nm and 8 nm respectively. The characteristic peak at 482 cm-1 of the Ti–O bond stretching vibrations can be evidently observed from FTIR analysis. The Raman blue shift was found in the Fe doped TiO2 samples. Fe-doped TiO2 nanoparticles showed a significant red-shift in band edge as compared with pure TiO2 nanoparticles. The redshift of band gap was detected in Fe doped TiO2 nanoparticles. The photoluminescence (PL) emission intensity of Fe doped TiO2 nanoparticles decreases with an increase in Fe doping concentration. The photocatalytic efficiencies of the Fe-doped TiO2 nanoparticles have shown a strong photocatalytic activity (PCA) response. At constant irradiation time, the Fe-doped titania nanoparticles display more catalytic activity compared to undoped TiO2. The photodegradation efficiencies typically decline with an increase in the concentration of Fe+3 doping for the decolorization of methylene blue (MB) under visible light irradiation.
关键词： band gap,Raman modes,photocatalytic activity,TiO2 nanoparticles,methylene blue,PL emission
更新于2025-11-21 11:18:25
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Effect of Annealing Temperature on Structural, Morphological, Optical and Electrical Properties of Spray Deposited V2O5 Thin Films
摘要： Nanostructured vanadium pentoxide (V2O5) thin films have been deposited by a simple and cost-effective spray pyrolysis technique (SPT) at substrate temperature 300 °C and post annealed at atmospheric conditions in the temperature range from 300 °C to 500 °C at a constant rate of heating. The influence of post annealing heat treatment on the crystallization of V2O5 has been investigated. Films were characterized structurally by X-ray diffraction, morphologically by Scanning electron microscopy, optically using UV-Vis spectrophotometer, electrical characterization using Hall probe and Raman spectroscopy has been carried out for phase confirmation. X-ray diffraction analysis (XRD) revealed that, as deposited films were orthorhombic structures with a preferential orientation along (0 0 1) direction. Moreover, it was observed that crystallite size increases from 22 nm to 56 nm with increase in annealing temperature. Optical properties of these samples were studied in the wavelength range 300 – 1000 nm. Raman spectrum confirms the layered structure of V2O5 thin films. Hall Effect measurements indicate that the change in carrier concentration with increase in annealing temperature.
关键词： Raman spectroscopy,carrier density,annealing temperature,V2O5
更新于2025-11-21 11:18:25
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Optimized signal-to-noise ratio with shot noise limited detection in Stimulated Raman Scattering microscopy
摘要： We describe our set-up for Stimulated Raman Scattering (SRS) microscopy with shot noise limited detection for a broad window of biologically relevant laser powers. This set-up is used to demonstrate that the highest signal-to-noise ratio (SNR) in SRS with shot noise limited detection is achieved with a time-averaged laser power ratio of 1:2 of the unmodulated and modulated beam. In SRS, two different coloured laser beams are incident on a sample. If the energy difference between them matches a molecular vibration of a molecule, energy can be transferred from one beam to the other. By applying amplitude modulation to one of the beams, the modulation transfer to the other beam can be measured. The efficiency of this process is a direct measure for the number of molecules of interest in the focal volume. Combined with laser scanning microscopy, this technique allows for fast and sensitive imaging with sub-micrometre resolution. Recent technological advances have resulted in an improvement of the sensitivity of SRS applications, but few show shot noise limited detection. The dominant noise source in this SRS microscope is the shot noise of the unmodulated, detected beam. Under the assumption that photodamage is linear with the total laser power, the optimal SNR shifts away from equal beam powers, where the most signal is generated, to a 1:2 power ratio. Under these conditions the SNR is maximized and the total laser power that could induce photodamage is minimized. Compared to using a 1:1 laser power ratio, we show improved image quality and a signal-to-noise ratio improvement of 8 % in polystyrene beads and C. Elegans worms. Including a non-linear damage mechanism in the analysis, we find that the optimal power ratio converges to a 1:1 ratio with increasing order of the non-linear damage mechanism.
关键词： shot noise limited detection,signal-to-noise ratio,Nonlinear Raman microscopy
更新于2025-11-21 11:08:12
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AIP Conference Proceedings [Author(s) CURRENT TRENDS IN RENEWABLE AND ALTERNATE ENERGY - Guwahati, India (4–6 December 2018)] - Study of laser induced micro-structural changes in reduced graphene oxide
摘要： Graphene is a promising 2D material for solar cell and energy storage applications. Graphene based materials such as Graphene oxide (GO) are proposed as anode materials for Lithium ion batteries, transparent conducting films, electrodes in polymer based solar cells and many other applications. The present paper discusses laser induced micro structural changes in reduced GO (r-GO) thin films. GO was prepared by Modified Hummers Method, which is easy and low cost method for its large-scale production. The samples were thermally annealed at 400°C to obtain r-GO. To study the influence of laser exposure on micro structure of r-GO, the Raman spectra was recorded after exposure to different time 2, 4, 6 and 8 minutes. Two different laser intensities (95 and 159 KW/cm2) were used to do the same. A blue shift in peak positions and change in ratio of intensity were observed in D and G peaks of Raman spectra after exposure. A total Raman blue shift of about 5 cm-1 is noted in each case, which is due to increased compressive stress between the carbon-carbon bonds. The Raman data was used for calculations of residual stress, grain size and defect density, which changes in gradual pattern with increase in power density and time of exposure. From these observations, it can be concluded that r-GO thin film undergoes micro-structural changes at exposed portion, without affecting rest of the film.
关键词： Graphene,Raman Spectroscopy,Reduced Graphene Oxide,Laser Induced Changes,Graphene Oxide
更新于2025-11-21 11:01:37