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Quantum dots of two-dimensional Ruddlesdena??Popper organica??inorganic hybrid perovskite with high optical limiting properties
摘要： Hybrid perovskites have been investigated for various potential applications because of their tunable optical properties. In this paper, we report the synthesis of quantum dots (QDs) of two-dimensional (2D) Ruddlesden–Popper (RP) hybrid perovskite using a top-down approach. The QDs of the developed 2D RP perovskite exhibit high and sharp photoluminescence in the ultraviolet region. The sharp peak in the absorption spectrum and the intense photoluminescence in the ultraviolet region indicate strong quantum confinement in these particles, which is further confirmed by x-ray photoelectron spectroscopy. These QDs show superior nonlinear optical scattering and absorption properties with the optical z-scan technique and strong nonlinear absorption property with the photoacoustic z-scan technique. Evaluating the nonlinear optical properties using two complementary techniques provides a deeper understanding of the nonlinear mechanism involved in the optical limiting process. The two-photon absorption coefficient obtained by optical z-scan is 7.2 × 102 cm/GW, which is larger than that of most perovskite nanocrystals and nanosheets. Our studies, therefore, reveal a new class of material, 2D RP perovskite QDs, which show important nonlinear properties that are important for optical limiting applications.
关键词： Ruddlesden–Popper perovskite,optical limiting,nonlinear optical properties,Quantum dots,two-photon absorption
更新于2025-09-23 15:21:01
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High-contrast, fast chemical imaging by coherent Raman scattering using a self-synchronized two-colour fibre laser
摘要： Coherent Raman scattering (CRS) microscopy is widely recognized as a powerful tool for tackling biomedical problems based on its chemically specific label-free contrast, high spatial and spectral resolution, and high sensitivity. However, the clinical translation of CRS imaging technologies has long been hindered by traditional solid-state lasers with environmentally sensitive operations and large footprints. Ultrafast fibre lasers can potentially overcome these shortcomings but have not yet been fully exploited for CRS imaging, as previous implementations have suffered from high intensity noise, a narrow tuning range and low power, resulting in low image qualities and slow imaging speeds. Here, we present a novel high-power self-synchronized two-colour pulsed fibre laser that achieves excellent performance in terms of intensity stability (improved by 50 dB), timing jitter (24.3 fs), average power fluctuation (<0.5%), modulation depth (>20 dB) and pulse width variation (<1.8%) over an extended wavenumber range (2700–3550 cm?1). The versatility of the laser source enables, for the first time, high-contrast, fast CRS imaging without complicated noise reduction via balanced detection schemes. These capabilities are demonstrated in this work by imaging a wide range of species such as living human cells and mouse arterial tissues and performing multimodal nonlinear imaging of mouse tail, kidney and brain tissue sections by utilizing second-harmonic generation and two-photon excited fluorescence, which provides multiple optical contrast mechanisms simultaneously and maximizes the gathered information content for biological visualization and medical diagnosis. This work also establishes a general scenario for remodelling existing lasers into synchronized two-colour lasers and thus promotes a wider popularization and application of CRS imaging technologies.
关键词： Coherent Raman scattering,CRS microscopy,biomedical imaging,fibre laser,nonlinear optical imaging
更新于2025-09-23 15:21:01
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The laser field controlling on the nonlinear optical specifications of the electric field-triggered Rosen-Morse quantum well
摘要： We consider, for the first time, optical specifications such as the nonlinear optical rectification (NOR), the second harmonic generation (SHG) and the third harmonic generation (THG) of quantum well (QW) that has the Rosen-Morse potential confinement and is generated by GaAs/GaAlAs heterostructure. To do this, QW structure is firstly asymmetrized by applying an external electric field, as 10 kV/cm. Therefore, the electric field-triggered (F = 10 kV/cm) Rosen-Morse QW (eftRMQW) is taken into consideration throughout the study. In this study, it is elucidated that how to control NOR, SHG and THG optical responses through monochromatic linearly polarized intense laser field (ILF). In order to be able to investigate the ILF effects, the time-dependent of ILF is removed to potential energy term of the wave equation by using Kramers-Henneberger (KH) and the dipole approximations, building the laser-dressed potential. Then, the bound state energies and the wave functions of eftRMQW are obtained using the diagonalization method within the effective mass approach and the parabolic approximation. The influences of the ILF and structural parameters of eftRMQW on NOR, SHG and THG coefficients are discussed in detail. The optimum of structure is ferreted out for devices design and applications that will consider eftRMQW, and for this optimum the alternative parameter analysis is carried out.
关键词： Nonlinear optical properties,Laser field,Electric field,Rosen-Morse quantum well
更新于2025-09-23 15:21:01
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Comprehensive modeling and design of Raman lasers on SOI for mid-infrared application
摘要： In this paper, we present a comprehensive model for a CW Raman laser in a silicon-on-insulator (SOI) platform. We validate this model by comparing its output with experimental results from the literature. We then design a 2.232 μm Raman laser with an on-chip ring resonator cavity. Numerical analysis of laser characteristics, such as threshold power and output power, are conducted. The optimized values for the cavity length and power coupling ratios are determined taking into account fabrication variations. Finally, by designing a tunable directional coupler (DC) for the laser cavity, a robust design of Raman laser is presented. We show that the reduction of propagation loss down to 0.6 dB/cm for the silicon waveguides and free carriers removal, by the use of a p-i-n junction, will enable a Raman laser with a threshold power of 16 mW and a slope efficiency of 62%.
关键词： Nonlinear optical devices,Raman scattering,Ring lasers
更新于2025-09-23 15:21:01
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Passively Q-switched laser with specific chiral SWCNTs selected by N-CS as saturable absorber at
摘要： The single-wall carbon nanotubes (SWCNTs) with the specific chirality (6, 5) and (7, 5) were sorted out by the density gradient ultracentrifugation (DGU) method. 2D photoluminescence excitation–emission map and the Raman spectrum confirmed the successful chirality-selection. The nonlinear optical performance of the chirality-selected SWCNTs was investigated by an open-aperture Z-scan setup. By employing the prepared SWCNTs saturable absorber (SWCNTs-SA), the minimum pulse duration of 115 ns with a pulse repetition rate of 550 kHz was obtained in the passively Q-switched (PQS) laser operation.
关键词： Q-switching,Chirality selection,Nonlinear optical properties,SWCNTs
更新于2025-09-23 15:21:01
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Nonlinear Optics || Quantum-Mechanical Theory of the Nonlinear Optical Susceptibility
摘要： In this chapter, we use the laws of quantum mechanics to derive explicit expressions for the nonlinear optical susceptibility. The motivation for obtaining these expressions is at least three-fold: (1) these expressions display the functional form of the nonlinear optical susceptibility and hence show how the susceptibility depends on material parameters such as dipole transition moments and atomic energy levels, (2) these expressions display the internal symmetries of the susceptibility, and (3) these expressions can be used to make predictions of the numerical values of the nonlinear susceptibilities. These numerical predictions are particularly reliable for the case of atomic vapors, because the atomic parameters (such as atomic energy levels and dipole transition moments) that appear in the quantum-mechanical expressions are often known with high accuracy. In addition, since the energy levels of free atoms are very sharp (as opposed to the case of most solids, where allowed energies have the form of broad bands), it is possible to obtain very large values of the nonlinear susceptibility through the technique of resonance enhancement. The idea behind resonance enhancement of the nonlinear optical susceptibility is shown schematically in Fig. 3.1.1 for the case of third-harmonic generation. In part (a) of this figure, we show the process of third-harmonic generation in terms of the virtual levels introduced in Chapter 1. In part (b) we also show real atomic levels, indicated by solid horizontal lines. If one of the real atomic levels is nearly coincident with one of the virtual levels of the indicated process, the coupling between the radiation and the atom becomes particularly strong and the nonlinear optical susceptibility becomes large.
关键词： resonance enhancement,quantum mechanics,nonlinear optical susceptibility,third-harmonic generation,dipole transition moments,atomic energy levels
更新于2025-09-23 15:21:01
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Nonlinear Optics || Molecular Origin of the Nonlinear Optical Response
摘要： In Chapter 3, we presented a general quantum-mechanical theory of the nonlinear optical susceptibility. This calculation was based on time-dependent perturbation theory and led to explicit predictions for the complete frequency dependence of the linear and nonlinear optical susceptibilities. Unfortunately, however, these quantum-mechanical expressions are typically far too complicated to be of use for practical calculations. In this chapter we review some of the simpler approaches that have been implemented to develop an understanding of the nonlinear optical characteristics of various materials. Many of these approaches are based on understanding the optical properties at the molecular level. We also present brief descriptions of the nonlinear optical characteristics of conjugated polymers, chiral molecules, and liquid crystals.
关键词： chiral molecules,nonlinear optical susceptibility,liquid crystals,quantum-mechanical theory,conjugated polymers,time-dependent perturbation theory
更新于2025-09-23 15:21:01
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Mid-infrared saturated absorption spectroscopy inside a hollow glass waveguide
摘要： We report the saturation spectroscopy of carbon dioxide inside a hollow glass waveguide (GW) using a tunable mid-infrared difference frequency generation (DFG) source. This DFG source was generated in a periodically poled lithium niobate crystal with a tuning range from 3.97 to 4.71 μm. Saturated spectroscopy was performed on the R(60) transition of CO20001 ← 0000 band at 4.2 μm inside a hollow GW of diameter 300 μm and length 1 m. The saturation dip signal was found with a pump power as low as 0.18 mW inside the hollow GW. The linewidth of the dip was determined to be 4.40 MHz.
关键词： Nonlinear optical interaction,Mid-infrared,Saturation spectroscopy,Hollow glass waveguide
更新于2025-09-23 15:21:01
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Direct mineralogical imaging of economic ore and rock samples with multi-modal nonlinear optical microscopy
摘要： Multi-modal nonlinear optical (NLO) microscopy, including stimulated Raman scattering (SRS) and second harmonic generation (SHG), was used to directly image mineralogical features of economic ore and rock samples. In SRS/SHG imaging, ore samples generally require minimal preparation and may be rapidly imaged, even in their wet state. 3D structural details, at submicron resolution, are revealed tens of microns deep within samples. Standard mineral imaging based on scanning electron microscopy (SEM), with elemental analysis via energy dispersive X-Ray spectroscopy, was used to independently validate the mineral composition of the samples. Spatially-resolved SRS from dominant Raman-resonant bands precisely maps the locations of specific minerals contained within the samples. SHG imaging reveals locally non-centrosymmetric structures, such as quartz grains. Competing absorption and nonlinear scattering processes, however, can reduce contrast in SRS imaging. Importantly, the correlation between standard electron microscopy and multi-modal NLO optical microscopy shows that the latter offers rapid image contrast based on the mineral content of the sample.
关键词： mineralogical imaging,second harmonic generation,stimulated Raman scattering,rock samples,nonlinear optical microscopy,economic ore
更新于2025-09-23 15:21:01
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Enhanced nonlinear optical behavior of graphene-CuO nanocomposites investigated by Z-scan technique
摘要： Graphene-CuO nanocomposites were synthesized by the solvothermal method, and graphene (G) were prepared for comparison. The morphologies and structures of samples were investigated by x-ray diffraction, scanning electron microscopy, Raman spectroscopy and ultraviolet-visible absorption spectroscopy. The nonlinear optical (NLO) properties were tested by the Z-scan technology with 1030 nm laser pulses (340 fs, 1000 Hz). The analyse demonstrates that the NLO properties of the graphene-CuO nanocomposites are significantly enhanced compared with graphene, the doping of CuO increases the time of the electron transfer and the photon transition, suppress the recombination between electrons and holes, and prolong the working time of the free carrier, ultimately enhance the nonlinear optical properties of nanocomposites. The results provide a facile approach of doping CuO in graphene to obtain nanocomposites with excellent NLO properties, and the nanocomposites exhibited potential applications in optical devices such as optical switch and optical sensors, etc.
关键词： Nonlinear optical properties,Z-scan technology,Nanocomposites
更新于2025-09-23 15:21:01