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- 2019
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- plane-layered stratified medium
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- GPR
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- White pigment (R902+)
- Optoelectronic Information Science and Engineering
- Optoelectronic Information Materials and Devices
- V. N. Karazin Kharkiv National University
- Kharkiv National Automobile and Highway University
- Tribhuvan University
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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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Large-Dynamic Frequency Response Measurement for Broadband Electro-Optic Phase Modulators
摘要： A novel method for characterizing the frequency responses of broadband electro-optic phase modulators (PMs) by employing stimulated Brillouin scattering (SBS) is proposed and experimentally demonstrated. In the proposed method, the SBS amplifies the +1st-order sideband and attenuates the -1st-order sideband of the phase-modulated signal from a PM under test. Thereby, the phase-modulated signal is converted into an optical single-sideband (OSSB) modulation signal. After square-law photodetection, the overall frequency responses are obtained. Removing the frequency responses of the SBS gain and the photodetector (PD) from the overall responses, the responses of the PM are thus achieved. Benefitting from the amplification of the SBS, the proposed method possesses a large dynamic range. Sub-Hz resolution and broadband measurement range are also achievable. A commercial broadband PM is experimentally characterized from 10 MHz to 50 GHz with a resolution of 5 MHz. According to the amplification of the SBS, the dynamic range is enhanced by 17.74 dB. The measurement result is verified by the conventional method utilizing optical spectrum analysis.
关键词： stimulated Brillouin scattering,Electrooptic modulation,Phase modulation,microwave photonics,optical variables measurement
更新于2025-11-28 14:24:03
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Self-generating Brillouin fiber laser using highly nonlinear hafnium bismuth erbium-doped fiber
摘要： A compact Brillouin fiber laser (BFL) utilizing a newly developed hafnium bismuth erbium-doped fiber (HB-EDF), which functions as both the Brillouin and linear gain media, is realized in the absence of Brillouin pump. It is achieved by the self-Brillouin generation from a 0.2 m length of HB-EDF with high nonlinearity in a laser cavity. The self-generating BFL was obtained in both ring and linear laser cavities. Compared to the ring cavity, the BFL in the linear cavity produced more Brillouin stokes at a lower pump threshold. In the experiment, an eight-line comb with average spacing of 0.087 nm was generated at the HB-EDF pump power of 75.27 mW. This compact BFL has total cavity length of less than 0.5 m, and thus, this is the shortest gain medium reported.
关键词： hafnium bismuth erbium-doped fiber,self-generating Brillouin fiber laser,stimulated Brillouin scattering
更新于2025-11-28 14:23:57
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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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Multipole Radiations from Large Gold Nanospheres Excited by Evanescent Wave
摘要： We proposed the use of the evanescent wave generated in a total internal reflection configuration to excite large gold nanospheres and investigated the radiations of the high-order plasmon modes supported in gold nanospheres. It was revealed that the evanescent wave excitation is equivalent to the excitation by using both the incident and reflected light, offering us the opportunity to control the orientation of the electric field used to excite nanoparticles. In addition, it was found that the scattering light intensity is greatly enhanced and the background noise is considerably suppressed, making it possible to detect the radiations from high-order plasmon modes. Moreover, the influence of the mirror images on the scattering induced by a metal substrate is eliminated as compared with the surface plasmon polariton excitation. By exciting a gold nanosphere with s-polarized light and detecting the scattering light with a p-polarized analyzer, we were able to reveal the radiation from the electric quadrupole mode of the gold nanosphere in both the spatial and the frequency domains. Our findings are important for characterizing the radiations from the high-order modes of large nanoparticles and useful for designing nanoscale photonic devices.
关键词： scattering,plasmon mode,electric dipole,radiation pattern,gold nanosphere,evanescent wave,electric octupole,electric quadrupole
更新于2025-11-21 11:24:58
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Superior light harnessing and charge injection kinetics utilizing mirror-like nano cuboidal ceria coupled with reduced graphene oxide in zinc oxide nanoparticle based photovoltaics
摘要： Efficiency in nanoparticle based photovoltaics is limited by optical transparency, light absorption as well as detrimental back transfer of electron at the hetero-interfaces. Three dimensional (3D) micro/nanostructures with excellent light scattering properties play pivotal role in light harvesting efficiency in DSSCs. Present study deals with the design and development of ternary hybrid photoanode utilizing high quality mirror like nano-cuboidal ceria (CeO2 NC) and 2D- reduced graphene oxide (RGO) sheets in conjunction with ZnO nanoparticle. A ～6% power conversion efficiency has been achieved for photoanode with optimized CeO2 NC loaded with 1 wt% RGO into ZnO NP. CeO2 NC owing to its size and high quality mirror like facets provides a better light harvesting by multiple interactions of incident photon with the absorber as revealed by UV–Vis diffused reflectance and IPCE analysis. 2D- RGO is proposed to act as an electron sink and provides faster electron transport pathway. Inclusion of 2D- RGO sheets yields a better charge injection kinetics (keinj ～ 2.3 × 108 s?1 for ternary, 1.1 × 108 s?1 for reference device) and collection at FTO as well as elevated recombination resistance (Rrec) and photo-induced electron life time (τe), unveiled by Electrochemical Impedance Spectroscopic (EIS) analysis corroborates a reduced reverse tunneling of photo-injected electron at ZnO/sensitizer/redox couple interface.
关键词： Diffusion,Mirror-like,Light scattering material,Reduced graphene oxide,Electrochemical impedance spectroscopy,Nano cuboidal
更新于2025-11-21 11:01:37
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Dopamine-Mediated Assembly of Citrate-Capped Plasmonic Nanoparticles into Stable Core-Shell Nanoworms for Intracellular Applications
摘要： Plasmonic nanochains, derived from the one-dimensional assembly of individual plasmonic nanoparticles (NPs), remain infrequently explored in biological investigations due to their limited colloidal stability, ineffective cellular uptake, and susceptibility to intracellular disassembly. We report the synthesis of polydopamine (PDA)-coated plasmonic “nanoworms” (NWs) by sonicating citrate-capped gold (Cit-Au) NPs in a concentrated dopamine (DA) solution under alkaline conditions. DA mediates the assembly of Cit-Au NPs into Au NWs within 1 min, and subsequent self-polymerization of DA for 60 min enables the growth of an outer conformal PDA shell that imparts stability to the inner Au NW structure in solution, yielding “core–shell” Au@PDA NWs with predominantly 4–5 Au cores per worm. Our method supports the preparation of monometallic Au@PDA NWs with different core sizes and bimetallic PDA-coated NWs with Au and silver cores. The protonated primary amine and catechol groups of DA, with their ability to interact with Cit anions via hydrogen bonding and electrostatic attraction, are critical to assembly. When compared to unassembled PDA-coated Au NPs, our Au@PDA NWs scatter visible light and absorb near-infrared light more intensely, and enter HeLa cancer cells more abundantly. Au@PDA NWs cross the cell membrane as intact entities primarily via macropinocytosis, mostly retain their inner NW structure and outer PDA shell inside the cell for 24 h, and do not induce noticeable cytotoxicity. We showcase three intracellular applications of Au@PDA NWs, including label-free dark-field scattering cell imaging, delivery of water-insoluble cargos without pronounced localization in acidic compartments, and photothermal killing of cancer cells.
关键词： 1D assembly,citrate-capped nanoparticles,polydopamine coating,photothermal killing,intracellular delivery,plasmonic nanoworms,dark-field scattering imaging
更新于2025-11-19 16:56:42
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Core-Shell Modeling of Light Scattering by Vesicles: Effect of Size, Contents, and Lamellarity
摘要： Having a fast, reliable method for characterizing vesicles is vital for their use as model cell membranes in biophysics, synthetic biology, and origins of life studies. Instead of the traditionally used Rayleigh-Gans-Debye approximation, we use an exact extended Lorenz-Mie solution for how core-shell particles scatter light to model vesicle turbidity. This approach enables accurate interpretations of simple turbidimetric measurements and is able to accurately model highly scattering vesicles, such as larger vesicles, those with multiple layers, and those with encapsulated material. We uncover several surprising features, including that vesicle lamellarity has a larger effect on sample turbidity than vesicle size and that the technique can be used to measure the membrane thickness of vesicles. We also examine potential misinterpretations of turbidimetry and discuss when measurements are limited by forward and multiple scattering and by the geometry of the instrument.
关键词： Lorenz-Mie theory,turbidimetry,membrane thickness,vesicles,lamellarity,light scattering
更新于2025-11-19 16:56:35
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Three-dimensional Nanoscale Mapping of Porosity in Solution-Processed ITO Multilayer Thin Films for Patternable Transparent Electrodes
摘要： Indium tin oxide (ITO) films constitute components of many layered heterostructures used for emergent technologies beyond conventional optoelectronics. Compositional and morphological changes have a direct impact on the device’s performance. Hence control over the morphology with advanced multimodal characterization approaches are required to evaluate the devices. Herein multilayer ITO films deposited by spin coating were quantified in nanoscale detail in three dimensions by combining results from depth-sensitive neutron reflectometry (NR), non-contact topographic AFM images and cross-sectional SEM images. Films with different number of deposited layers were visually transparent even though the topmost layer was as high as 60% porous, with porosity gradually decreasing as the number of the underneath sublayers increased. Surface and interfacial roughness through the total film and individual layer thickness were obtained. NR data also furnished quantitative depth information on the films chemical composition and layer-by-layer bulk density, which has never been obtained before, providing a way to monitor and ultimately control the sheet resistivity via the pore network. When the same formulation is used for inkjet printing patterns, the larger pores disappear and the optical properties are improved to >90% transmittance at all visible wavelengths. All 5L films achieved sheet resistivities as low as 10-2 ?-cm and can therefore be used as patternable transparent electrodes for many devices including liquid crystal displays.
关键词： thin multilayer film,neutron reflectometry,depth density distribution,neutron absorption reflectometry,Indium tin oxide,porosity,structure chemical depth profile,off-specular neutron scattering,layer by layer deposition
更新于2025-11-19 16:56:35
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Atmospheric Pressure Plasma Synthesized Gold Nanoparticle/Carbon Nanotube Hybrids for Photo-thermal Conversion
摘要： In this work, a room temperature atmospheric pressure direct-current plasma has been deployed for the one-step synthesis of gold nanoparticle/carboxyl group functionalized carbon nanotube (AuNP/CNT-COOH) nanohybrids in aqueous solution for the first time. Uniformly distributed AuNPs are formed on the surface of CNT-COOH, without the use of reducing agents or surfactants. The size of the AuNP can be tuned by changing the gold salt precursor concertation. UV-Vis, ζ-potential and X-ray photoelectron spectroscopy suggest that carboxyl surface functional groups on CNTs served as nucleation and growth sites for AuNPs and the multiple potential reaction pathways induced by the plasma-chemistry have been elucidated in detail. The nanohybrids exhibit significantly enhanced Raman scattering and photothermal conversion efficiency, properties that are essential for potential multi-modal cancer treatment applications.
关键词： Surface Enhanced Raman Scattering,Gold Nanoparticles,Photothermal Conversion,Carbon Nanotubes,Plasma Synthesis
更新于2025-11-19 16:56:35