Raman Light Research Articles

Advanced Imaging Integration: Multi-Modal Raman Light Sheet Microscopy Combined with Zero-Shot Learning for Denoising and Super-Resolution.

This study presents an advanced integration of Multi-modal Raman Light Sheet Microscopy with zero-shot learning-based computational methods to significantly enhance the resolution and analysis of complex three-dimensional biological structures, such as 3D cell cultures and spheroids. The Multi-modal Raman Light Sheet Microscopy system incorporates Rayleigh scattering, Raman scattering, and fluorescence detection, enabling comprehensive, marker-free imaging of cellular architecture. These diverse modalities offer detailed spatial and molecular insights into cellular organization and interactions, critical for applications in biomedical research, drug discovery, and histological studies. To improve image quality without altering or introducing new biological information, we apply Zero-Shot Deconvolution Networks (ZS-DeconvNet), a deep-learning-based method that enhances resolution in an unsupervised manner. ZS-DeconvNet significantly refines image clarity and sharpness across multiple microscopy modalities without requiring large, labeled datasets, or introducing artifacts. By combining the strengths of multi-modal light sheet microscopy and ZS-DeconvNet, we achieve improved visualization of subcellular structures, offering clearer and more detailed representations of existing data. This approach holds significant potential for advancing high-resolution imaging in biomedical research and other related fields.

Comprehensive study of optical contrast, reflectance, and Raman spectroscopy of multilayer graphene

Graphene research has developed quite rapidly partially because even a monatomic layer can be visualized with a conventional optical microscope. Although optical properties of multilayer graphene such as optical contrast, reflectance (R), and Raman scattering have been well studied, they are studied independently and the thickness dependence is limited to a rather thin region. In this paper, the evolution of optical properties by thickness from monolayer to multilayer graphene up to 107 nm thick is studied comprehensively. The empirically known change of color of multilayer graphene is confirmed from the R, G and B intensities extracted from the optical images. It is also found that, as far as R for visible light is concerned, multilayer graphene is not necessarily considered as a layered material, and the refractive index for monolayer graphene is applicable even for the thickest multilayer graphene flake in this study. On the other hand, the layered structure and Raman scattering at each layer are essential to reproduce the G-band intensity of Raman scattering (I(G)). Not only the multiple reflection but also the interference of scattered Raman light should be considered for I(G) of multilayer graphene thicker than ∼30 nm.

High-efficiency anti-stokes Raman blue laser in CO2 enables high-luminance RGB laser-driven white light

Stimulated Raman scattering (SRS) is an efficient nonlinear frequency conversion method, enabling simultaneous generation of red, green, and blue (RGB) lasers. In order to synthesize a white light source for laser display by SRS, a 532 nm laser was used as pump source, and high purity gaseous carbon dioxide (CO2) was used as the Raman active medium. First, by optimizing experimental parameters, with an f = 1.5 m focal lens, in 0.8 atm CO2 pumped at 304 mJ, a first-order anti-Stokes (AS1) 495 nm blue laser was achieved, with an energy of 31.9 mJ, peak power of 10.9 MW and conversion efficiency (CE) of 10.5 %. Then, Then, the second-order Stokes light (S2) at 624 nm, residual pump laser (S0) at 532 nm, and AS1 laser were utilized as RGB primary colors. By the variation of pressure below 1 atmosphere (atm), the laser-driven white light (LDWL) with adjustable correlated color temperature (CCT) below 4700 K were simulated. Finally, LDWL up to 2.6 × 1018cd/m2 of a CCT of 3300 K could be synthesized at an RGB power ratio of PR: PG: PB = 0.447:0.094:0.459, resulting in a white light power CE of 44.4 % and luminous efficacy of 113.7 lm/W. In addition, use of the 574 nm yellow Raman light is expected to realize a four-primary (RGBY) laser display scheme with higher Luminance and broader color gamut. Moreover, the feasibility of using a 515 nm Yb: YAG laser as pump source to widen the range of CCT and improve the brightness of LDWL was discussed.

5.4 W, 2.35 µm cascaded Raman fiber laser pumped by dissipative soliton resonance-like pulses

We present a nonlinear amplifying loop mirror-based mode-locked fiber laser. By adjusting the pump power, the proposed laser exhibits a dissipative soliton resonance (DSR)-like pulse operation with a maximum pulse width of 150 ns. Subsequently, a three-stage Tm3+-doped fiber amplifier is implemented using a single-mode double-cladding Tm3+-doped fiber to increase the DSR-like pulse output power to 52.5 W, achieving a pump slope efficiency of 47.1% in the main amplifier. A 25 m first-order Raman-gain fiber (UHNA7) is pumped by a DSR-like pulse, and 16.3 W of pure 2.135 µm first-order Raman light with a spectral purity of 73.4% is obtained. Finally, 5.4 W of 2.35 µm second-order Raman light with a spectral purity of 66% is obtained using a 10 m 98% germania-core fiber as a second-order Raman-gain fiber cascaded after UHNA7 fiber. To the best of our knowledge, this is the highest output power ever obtained from a 2.3 µm laser.

Acoustic and optical phonons in quasi-two-dimensional MPS3 antiferromagnetic semiconductors

We report the results of the investigation of the acoustic and optical phonons in quasi-two-dimensional antiferromagnetic semiconductors of the transition metal phosphorus trisulfide family with Mn, Fe, Co, Ni, and Cd as metal atoms. The Brillouin–Mandelstam and Raman light scattering spectroscopies were conducted at room temperature to measure the acoustic and optical phonon frequencies close to the Brillouin zone center and the Γ−A high symmetry direction. The absorption and index of refraction were measured in the visible and infrared ranges using the reflectometry technique. We found an intriguing large variation, over ∼28%, in the acoustic phonon group velocities in this group of materials with similar crystal structures. Our data indicate that the full-width-at-half-maximum of the acoustic phonon peaks is strongly affected by the optical properties and the electronic bandgap. The acoustic phonon lifetime extracted for some of the materials was correlated with their thermal properties. The results are important for understanding the layered van der Waals semiconductors and assessing their potential for optoelectronic and spintronic device applications.

Efficient tunable cascaded Raman source with all-silica fibers based on 2-µm DSR pulse pumping.

We present an efficient tunable all-silica-fiber 2nd-order cascaded Raman pulse laser utilizing 2-µm dissipative-soliton-resonance (DSR) rectangular pulses for pumping and highly GeO2-doped silica fiber as Raman gain medium. When pumped at 1966.5 nm, the maximum 1st-order Raman optical conversion efficiency is up to 64.4% at 2153 nm, with 92.4% spectral purity and 0.39-W average power. The maximum 2nd-order Raman optical conversion efficiency is 19.3% at 2370 nm, with 39.2% spectral purity and 0.25-W average power. To our knowledge, these conversion efficiencies and spectral purities represent the highest levels achieved in a mid-infrared all-silica-fiber cascaded pulsed Raman laser. Additionally, by adjusting the central wavelength of the DSR seed pulse, the 2nd-order Raman light can be tuned within a range of 41 nm (2354∼2395 nm). Our system provides a simple and easy-to-implement solution for realizing efficient tunable cascaded pulsed Raman lasers in the 2.4-µm band.

Experiment and analysis of state preparation for atom interferometry

The state preparation is a crucial procedure in atom interferometry; however, there is a shortage of detailed experimental studies on determining the optimal method for achieving this. This paper investigates and compares two methods for state preparation: the combined use of microwave and Raman light (M-R) and the combined use of optical pumping, microwave, and Raman light (O-M-W). The experimental results demonstrate that the M-R method improves the efficiency of Raman transitions for atom interference, which is helpful in enhancing the contrast of the interference fringes. The O-M-R method increases the quantity of prepared atoms, thereby enhancing the signal-to-noise ratio of the detected signals. This work helps provide a useful experimental basis and reference for researchers to design a suitable state preparation scheme.

Study of the structure of graphene oxide obtained by oxidation of intercalated graphite compound by Raman light scattering method

This work shows the strategy of GO synthesis from intercalated graphite compound, rotation of the synthesis conditions was carried out, and the starting material and synthesis products were characterized in detail by a complex of physical and chemical methods: scanning electron microscopy, transmission electron microscopy, atomic force microscopy, Raman spectroscopy, and high-temperature catalytic oxidation. It was found by Raman spectroscopy that the initial IGC sample is a graphite structure with a low content of defects in graphene layers. Oxidation of this sample leads to a gradual increase in the measure of disordered carbon framework. One of the reasons for this is a decrease in the size of graphite-like crystallites with subsequent reorientation in the space of graphene layers. It has been established by a complex of physicochemical methods of research that the oxidation of IGC graphite with increasing oxidation time leads to an increase in the defectivity of the initial carbon framework due to a decrease in the linear size of carbon crystallites. When a certain reaction time is reached, the initial structure of the sample changes, and there is a partial reorientation of the crushed graphite-like fragments with a simultaneous increase in the number of defects.

Development of Operando Spectroscopy Measurement Technique for Single-Electrode Particle

ObjectiveSingle-particle electrochemical measurements have been desired to obtain essential electrochemical information on electrode materials. Currently, an electrochemical measurement method using micrometer order current-collecting probes (direct probe contact method) has been proposed to evaluate electrochemical properties for obtaining constant current charge-discharge and AC impedance data 1) 2). On the other hand, the structural change of electrode materials and their interfaced charge-discharge can be measured (Operando) by the spectroscopic method. Direct probe connection between polished microprobe and micrometer scale active material particle prevents sufficient irradiation of spectroscopic light, such as Raman light. This study uses the Operando technique of in-situ spectroscopic measurement for electrode active material particles under electrochemical reaction conditions by grasping a single active electrode particle with precision tweezers.ExperimentIn this study, a micromanipulator, motorized precision tweezer controller, precision tweezers (SUS), and electrochemical measurement device were installed in the dry box (Dew point is less than -76.0 ℃). As shown in Fig.1, a Li foil (counter/reference electrode Φ16 mm) was attached to the SUS cup, a separator impregnated with electrolyte (1 mol-LiFSA /kg-ethylene carbonate (EC)) was placed, and a single particle of LiCoO2 (LCO; particle size 20~30 μm) was grasped and fixed into the electrolyte. After confirm the stable electrode potential of the LCO single particle held by precision tweezers, various electrochemical measurements, and Raman spectroscopy measurements were performed during the charge-discharge process.Results and DiscussionFig.2 shows Raman spectra of LCO powder, electrolyte, and LCO single particle immersed electrolyte. Two sharp peaks originating from the Co-O stretching vibration and O-Co-O angular vibration3) were detected in the (Ⅰ) wavenumber range. In addition, a group of sharp peaks derived from electrolyte was observed in the range of (Ⅱ), attributed to the S-N-S stretching motion of FSA- and the O-C-O stretching motion of EC4). Therefore, this system enabled to obtain of Raman spectra of both LCO and electrolyte at the same time by using precision tweezers and a single particle. This technique enabled the observation of not only the structural changes of LCO according to charge-discharge reactions but also concentration changes owing to their changes in Li cation transport of the electrolyte at the electrode interface.To observe the solvation/desolvation behavior of the interface of electrolyte / Li metal, a micro-current collector (Cu wire: Φ 30 μm) was applied for a simplification experimental method, the Operando Raman spectroscopy measurements were performed during the Li deposition/dissolution test was conducted by cyclic voltammetry with the cell immersed in the electrolyte. The potential was swept to the negative side from OCV, and Raman spectra changed from 100mV to -100mV vs. Li/Li+. Li dendrites occurred below -100mV vs. Li/Li+, resulting in a change in focus and loss of the Raman peak. Fig.4 shows the Raman spectra at each potential between 100mV and -100mV vs. Li/Li+. Each peak in Fig.4(a) was attributed to the free FSA anion and the bound FSA anion, respectively, and peaks in Fig.4(b) were attributed to free EC and solvated EC. The change in Raman spectra of the EC peaks was larger than in the FSA anion ones. The fraction of integrated intensity of between free and solvated EC exhibited clearly change from around -50 mV. The fraction of integrated intensity of free and bound FSA anions also changed significantly from 2000 to 500 mV and rapidly returned to the initial state with the Li deposition reaction around -50 mV. From this result, the decrease in the Li cation with the dissolution reaction could be observed from the Raman peaks. Changing the dissociation properties of salt were observed from the changing peak of FSA anion. Smooth association of salt between FSA anion and Li cation was observed at initial state of Li dissolution process. We will report that sufficient metal plating will be applied to tweezers for direct observation of Raman spectra for electrolyte interface, charge-discharge tests, and obtained Raman spectra analysis results.1) K. Dokko et.al., J. Electrochem. Soc., 148, A422-A426 (2001).2) T. Saito et.al., J. Phys. Chem. C, 124, 16758-16762 (2020).3) L. Le Van-Jodin et.al., J. Raman Spectrosc., 50, 1594-1601 (2019).4) B. Klassen et.al., J. Phys. Chem. B, 102, 4795-4801 (1998). Figure 1

Analysis of the Principle and State-of-art Facilities of Mobile Atom Interferometry Gravity

With over 20 years of development, atomic interferometry gravimeters have distinguished themselves in gravity measurements by their high precision and sensitivity. To cater to the demands of field absolute gravity measurements for marine and aerial gravity field measurements, resource exploration, inertial navigation, and positioning, the miniaturization, mobility, and engineering of atomic interferometry gravimeters have become crucial areas of development. On this basis, this article elucidates the principles of atomic interferometry gravimeters, encompassing various laser cooling techniques, magneto-optical traps, and Raman light interference. As a matter of fact, it provides an overview of the principles and achieved precision benchmarks of portable, vehicular, airborne, and shipborne atomic interferometry gravimeters. Additionally, it analyzes the experimental content and results of maritime, terrestrial, and aerial experiments based on portable atomic interferometry gravimeters. The limitations of portable atomic interferometry gravimeters are discussed, along with an exploration of their application prospects. Overall, these results shed light on guiding further exploration of mobile atom interferometry gravity.

STRUCTURE, OPTICAL PROPERTIES AND PHOTOCATALYTIC ACTIVIYY OF UNDOPED, La2O3-DOPED ZnO NANOCOMPOSITES

La-doped ZnO nanocomposites with di­ffe­rent content of La2O3 (1–5%) were obtained by the Pechini method from their nitrate solutions. The solutions of Zn2+ and La3+ nitrates were preliminary obtained by dissolving of zinc and lanthanum oxides with a content of the main component of 99.99% in nitric acid. The influence of lanthanum doping the on the microstructure, morphology, optical pro­perties and photocatalytic activity of the ZnO nanopowders were examined. The properties of the nanopowders were studied by using X-ray phase analysis, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy. The samples were subjected to X-ray powder diffraction using a DRON-3 diffractometer (Cu-K radiation) at room temperature. The scan angle was 0.05–0.1 ° in the range 2 = 15–90 °. X-ray phase ana­lysis confirms the formation of single phase of La2O3-doped ZnO powders on diffractograms. Raman light scattering and photoluminescence spectra were recorded using a Horiba Jobin‑Yvon T64000 spectrometer equipped with a CCD detector at room temperature in the inverse scattering geometry. According to SEM results, the powders characterized a conglomerate structure. The undoped ZnO has an average particle size of 43 nm, while the average particle size of La3+-doped ZnO ranges from 64 to 80 nm. It was established that the morphology of powder particles primarily depends on the content of La3+ in the material. An increase in the amount of La3+ in zinc oxide leads to an increase in the specific surface area (from 3.8 to 11.8 m2/g). In the photoluminescence spectra of ZnO powders, with increasing La2O3 concentration, bands at 400 nm are observed due to the appearance of impurities that cause of interstitial zinc and zinc vacancy defects and their broade­ning with a shift to the long-wave region. Photocatalytic properties of ZnO pow­ders doped with lanthanum oxide were in­vestigated using Methyl Orange as a model dye under Osram Ultra-Vitalux lamp (300 W) irradiation. A present result indicates that the obtained powders are potential candidate for the practical application in photocatalysis.

Optical and acoustic phonons in turbostratic and cubic boron nitride thin films on diamond substrates

We report an investigation of the bulk optical, bulk acoustic, and surface acoustic phonons in thin films of turbostratic boron nitride (t-BN) and cubic boron nitride (c-BN) grown on B-doped polycrystalline and single-crystalline diamond (001) and (111) substrates. The characteristics of different types of phonons were studied using Raman and Brillouin-Mandelstam light scattering spectroscopies. The atomic structure of the films was determined using high-resolution transmission electron microscopy (HRTEM) and correlated with the Raman and Brillouin-Mandelstam spectroscopy data. The HRTEM analysis revealed that the cubic boron nitride thin films consisted of a mixture of c-BN and t-BN phases, with c-BN being the dominant phase. It was found that while visible Raman spectroscopy provided information for characterizing the t-BN phase, it faced challenges in differentiating the c-BN phase either due to the presence of high-density defects or the overlapping of the Raman features with those from the B-doped diamond substrates. In contrast, Brillouin-Mandelstam spectroscopy clearly distinguishes the bulk longitudinal and surface acoustic phonons of the c-BN thin films grown on diamond substrates. Additionally, the angle-dependent surface Brillouin-Mandelstam scattering data show the peaks associated with the Rayleigh surface acoustic waves, which have higher phase velocities in c-BN films on diamond (111) substrates. These findings provide valuable insights into the phonon characteristics of the c-BN and diamond interfaces and have important implications for the thermal management of electronic devices based on ultra-wide-band-gap materials.

Innovative Imaging Techniques: A Conceptual Exploration of Multi-Modal Raman Light Sheet Microscopy.

Advances in imaging of microscopic structures are supported and complemented by adaptive visualization tools. These tools enable researchers to precisely capture and analyze complex three-dimensional structures of different kinds such as crystals, microchannels and electronic or biological material. In this contribution, we focus on 3D cell cultures. The new possibilities can play a particularly important role in biomedical research, especially here in the study of 3D cell cultures such as spheroids in the field of histology. By applying advanced imaging techniques, detailed information about the spatial arrangement and interactions between cells can be obtained. These insights help to gain a better understanding of cellular organization and function and have potential implications for the development of new therapies and drugs. In this context, this study presents a multi-modal light sheet microscope designed for the detection of elastic and inelastic light scattering, particularly Rayleigh scattering as well as the Stokes Raman effect and fluorescence for imaging purposes. By combining multiple modalities and stitching their individual results, three-dimensional objects are created combining complementary information for greater insight into spatial and molecular information. The individual components of the microscope are specifically selected to this end. Both Rayleigh and Stokes Raman scattering are inherent molecule properties and accordingly facilitate marker-free imaging. Consequently, altering influences on the sample by external factors are minimized. Furthermore, this article will give an outlook on possible future applications of the prototype microscope.

Simple technique of coupling a diode laser into a linear power buildup cavity for Raman gas sensing.

We report a novel, to the best of our knowledge, and simple technique to lock a 642 nm multi-quantum well diode laser to an external linear power buildup cavity by directly feeding the cavity reflected light back to the diode laser for enhancement of gas Raman signals. The dominance of the resonant light field in the locking process is achieved by reducing the reflectivity of the cavity input mirror and thus making the intensity of the directly reflected light weaker than that of the resonant light. Compared with traditional techniques, stable power buildup in the fundamental transverse mode TEM00 is guaranteed without any additional optical elements or complex optical arrangements. An intracavity exciting light of 160 W is generated with a 40 mW diode laser. Using a backward Raman light collection geometry, detection limits at the ppm level are achieved for ambient gases (N2, O2) with an exposure time of 60 s.

High power noise-like pulse at 2 μm and its applications in mid-IR Raman light and flat supercontinuum

Herein, a high-power noise-like (NL) pulse fiber laser system in the 2 μm region and its applications in mid-IR Raman stokes light and flat supercontinuum (SC) were experimentally demonstrated. An all-PM fiber configuration oscillator was constructed as the seed source which can deliver stable NL mode-locked pulse trains centered at ∼1950 nm wavelength with ∼5.37 MHz repetition rate. The pulse envelope and coherence spike widths of the NL pulse can be tunable from ∼2.5 ns to ∼3.4 ns and ∼397 fs to ∼375 fs, respectively. Relying on the magnified NL pulse, the cascaded Raman shifted stokes lights centered at ∼2148 nm and ∼2359 nm were separately achieved. Meanwhile, a flat SC with a 10 dB bandwidth of ∼480 nm (from ∼1940 nm to ∼2420 nm) was obtained after boosting in a large-mode-area fiber amplifier stage, and the average output power of ∼72 W represents the highest output power of the NL pulse in the 2 μm region, to the best of our knowledge. Moreover, we noted that the NL pulse-based spectrum broadening is much more effective than that the picosecond pulse-based. Our experimental results strongly imply that the NL pulse can be severed as an ideal laser source for the application of mid-IR spectroscopy.

A line-scanning hyperspectral Raman microscope based on Bessel beam illumination.

Carbohydrate metabolism within the photosynthetic processes of plants plays a major role in plant performance. Current techniques for live imaging the structural characteristics of plants are often destructive or lack spatially explicit information. Raman spectroscopy is a nondestructive, label-free imaging technique which, in combination with Bessel beam light sheet microscopy, offers a way to rapidly measure the abundance and flux of molecules as they travel through the three dimensions of living plants. Here we describe the development of a Hyperspectral Raman Light Sheet Microscope as an alternative to traditional confocal point-scanning imaging systems. We cover our methods for creating a self-reconstructing Bessel beam to excite scattering in the sample, as well as modifications made to the conventional slit-spectrometer setup for capturing low intensity Raman scattered infrared light. We demonstrate the system with various test samples including Fluorinated Ethylene Propylene and Acetaminophen, and then discuss future applications in biological materials.

Features of Raman light scattering spectra in the 2100 cm-=SUP=--1-=/SUP=- line region by carbon formations in thin gradient gold films

Features of Raman light scattering spectra in the 2100 cm-=SUP=--1-=/SUP=- line region by carbon formations in thin gradient gold films

Research on chemical oxygen demand based on laser Fluorescence-Raman spectroscopy

In this invited paper, a novel water chemical oxygen demand (COD) detection method based on laser spectroscopy is proposed, and the COD value is obtained according to the intensity ratio of laser Fluorescence-Raman signal produced by laser incident into water. Based on the laser Fluorescence-Raman ratio (LFRR) method, we design a portable water quality measurement system. In which, a 405 nm semiconductor laser is used as the light source. The laser is coupled into the delivering port of Y-type fiber and then transmitted into water. The generated Mie scattered light, water Raman light and corresponding fluorescence are received and transmitted into spectrometer through the detecting port of Y-type fiber, and the COD value can be obtained by analyzing the LFRR of water spectra. The mixed solution of sodium humate and glucose is used as the COD standard solution to calibrate the designed system. The experiment results show that the optimal volume ratio of the two solutions is 1:29. When the COD of standard solutions is in the 1–12 mg/L concentration range, a good linear relationship can be found between the COD value and LFRR value with a correlation coefficient of 0.974. In addition, the COD of natural water samples are measured with LFRR method, the results of which are consistent with COD values obtained by rapid digestion spectrophotometry. Meanwhile, experimental results prove that the COD detection method proposed in this paper has the advantages of high sensitivity, high precision, high detection speed and simplicity, which can be widely used in various water areas for real-time COD monitoring.

Brillouin light scattering in niobium doped lead zirconate single crystal

Brillouin light scattering experiments were performed for lead zirconate single crystals doped with niobium. Special attention was paid to the elastic mode softening near phase transition temperatures. The results are compared with data obtained by Raman light scattering experiments. We observed that the interaction between acoustic and optic modes is responsible for symmetry breaking far above TC, leading to polar regions' appearance. No changes in the acoustic mode frequency and its damping are observed at TC, where ε(T) exhibits a maximum value. The absence of these changes and the central peak observed in Raman experiments suggest that the phase transition at TC is mainly of the order–disorder type. The origin of other phase transitions is discussed as well.

Robust single-sideband-modulated Raman light generation for atom interferometry by FBG-based optical rectangular filtration.

Low-phase-noise and pure-spectrum Raman light is vital for high-precision atom interferometry by two-photon Raman transition. A preferred and prevalent solution for Raman light generation is electro-optic phase modulation. However, phase modulation inherently brings in double sidebands, resulting in residual sideband effects of multiple laser pairs beside Raman light in atom interferometry. Based on a well-designed rectangular fiber Bragg grating and a plain electro-optic modulator, optical single-sideband modulation has been realized at 1560 nm with a stable suppression ratio better than -25 dB despite of intense temperature variations. After optical filtration and frequency doubling, a robust phase-coherent Raman light at 780 nm is generated with a stable SNR of better than -19 dB and facilitates measuring the local gravity successfully. This FBG-based all-fiber single-sideband-modulated Raman light source, proposed for the first time and characterized as robust, compact and low-priced, is practical and potential for field applications of portable atom interferometry.