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Raman Laser Switching Induced by Cascaded Light Scattering
摘要： It is shown that, in multimode Raman lasers, cascaded light scattering (CLS) not only extends the optical frequency range, but can also modulate the laser dynamics. The origin of this phenomenon lies in the fact that many Raman lasing modes are directly correlated through CLS. The coupled-mode equations only describe single-mode cascaded Raman lasers and are insufficient for describing the multimode case. In this work, additional terms are introduced to account for intermodal interaction and, therefrom the physical mechanism behind the mode-switching phenomenon is revealed. Additionally, mode-switching controlled solely by a single-mode pump in a whispering gallery mode (WGM) silica Raman laser is demonstrated. As the intracavity pump power is increased, laser switching happens between two adjacent WGMs in the same mode family.
关键词： cascaded light scattering,Raman lasers,mode switching,whispering gallery modes
更新于2025-09-19 17:13:59
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Upconverting TiO <sub/>2</sub> spheres with light scattering effect for enhanced quantum dot-sensitized solar cells
摘要： Semiconductor quantum dots (QDs) for solar cells could only absorb solar light in the visible region. Upconverters could convert near-infrared (NIR) photons into visible light photons that could be used to generate photocurrent by the sensitizers. Consequently, it is reasonable to utilize upconverters in the quantum dot-sensitized solar cells (QDSCs) in order to broaden the light utilization region. In this article, Yb3+/Er3+ co-doped TiO2 spheres were integrated into the photoanodes for QDSCs. The influence of photoanode configuration on the performance of the QDSCs has been scrutinized. The photoanode with the optimized composite film was employed to fabricate QDSC, yielding a conversion efficiency (η) of 3.53%. The QDSC with the composite film photoanode outperforms that with the pure TiO2 film photoanode. The amplified cell performance for the composite photoanodes could be attributed to the following two aspects: first, the upconversion process of the upconverter leads to indirect exploitation of NIR light. Second, the light scattering effect of the upconverter-doped TiO2 spheres enhances the absorption of visible light.
关键词： Quantum Dot-Sensitized Solar Cells,Yb3+/Er3+ Co-Doped TiO2,Upconversion,Light Scattering Effect
更新于2025-09-19 17:13:59
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The Effect of Capsulotomy Shape on Intraocular Light-Scattering after Nd:YAG Laser Capsulotomy
摘要： Purpose. To investigate the effects of capsulotomy shape on the visual acuity and visual quality after neodymium: yttrium aluminum garnet laser capsulotomy. Methods. In this study, a total of 42 eyes from 35 patients with posterior capsule opacification were divided into the circular and cruciate groups. The corrected distance visual acuity (CDVA), objective scatter index (OSI), modulation transfer function cutoff (MTF cutoff), Strehl ratio, and Optical Quality Analysis System values at contrasts of 100%, 20%, and 9% (OV-100, OV-20, and OV-9) were measured at precapsulotomy and 1 week and 1 month postcapsulotomy. The pseudophakic dysphotopsia questionnaire (PDQ) was used to evaluate the subjects’ satisfaction with treatment. Results. OSI values were significantly higher in the cruciate group than in the circular group at 1 week and 1 month after capsulotomy (P = 0.013 and P < 0.001). No significant difference was found in the OSI values between the two groups before capsulotomy (t = 0.52; P = 0.61). The decrease in OSI was higher in the circular group than in the cruciate group at 1 week and 1 month after capsulotomy (P = 0.036 and P = 0.019). No significant differences were found in the Strehl ratio, MTF cutoff, CDVA, OV-100, OV-20, and OV-9 between the two groups at 1 week and 1 month after capsulotomy (P > 0.05). The PDQ results showed that patients with circular-shaped capsulotomy complained less with intolerance of bright lights than those with cruciate-shaped capsulotomy. Conclusions. Circular-shaped capsulotomy can induce less intraocular light scattering and increase patient satisfaction.
关键词： visual acuity,Nd:YAG laser capsulotomy,visual quality,intraocular light-scattering,capsulotomy shape
更新于2025-09-19 17:13:59
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Structural and optical properties of nanoparticles formed by laser ablation of porous silicon in liquids: Perspectives in biophotonics
摘要： The paper discusses the possibility of manufacturing silicon nanoparticles, which are suitable for contrasting biological tissues imaged by optical coherence tomography, by femtosecond laser ablation of porous silicon in various liquids. The manufactured nanoparticles are characterised by average sizes of 87, 112, and 102 nm for cases of ablation in water, ethanol, and liquid nitrogen, respectively, as well as a relatively narrow size distribution, which provides additional advantages for subsequent delivery into biological tissues. Electro chemical etching, which results in the formation of layers of porous silicon, allows the yield of ablation products to be increased several-fold by lowering the ablation threshold, thereby increasing the light scattering efficiency of the prepared suspensions compared with the case of using crystalline silicon as targets. The possibility of obtaining high-contrast images of a biotissue phantom based on an agar gel with embedded nanoparticles is shown. The magnitude of the contrast depends on the liquid used for ablation and correlates with the values of the reduced scattering coefficient of the studied suspensions.
关键词： silicon nanoparticles,laser ablation in liquids,atomic force microscopy,light scattering,optical coherence tomography,spectrophotometry
更新于2025-09-19 17:13:59
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Coupling and Trapping of Light in Thin-Film Solar Cells Using Modulated Interface Textures
摘要： Increasing the e?ciency of solar cells relies on light management. This becomes increasingly important for thin-?lm technologies, but it is also relevant for poorly absorbing semiconductors like silicon. Exemplarily, the performance of a-Si:H/μc-Si:H tandem solar cells strongly depends on the texture of the front and rear contact surfaces. The rear contact interface texture usually results from the front surface texture and the subsequent absorber growth. A well-textured front contact facilitates light-coupling to the solar cell and light-trapping within the device. A variety of di?erently textured ZnO:Al front contacts were sputter deposited and subsequently texture etched. The optical performance of a-Si:H/μc-Si:H tandem solar cells were evaluated regarding the two e?ects: light-coupling and light-trapping. A connection between the front contact texture and the two optical e?ects is demonstrated, speci?cally, it is shown that both are induced by di?erent texture properties. These ?ndings can be transferred to any solar cell technologies, like copper indium gallium selenide (CIGS) or perovskites, where light management and modi?cations of surface textures by subsequent ?lm growth have to be considered. A modulated surface texture of the ZnO:Al front contact was realized using two etching steps. Improved light-coupling and light-trapping in silicon thin-?lm solar cells lead to 12.5% e?ciency.
关键词： thin-?lm solar cell,light-trapping,ZnO:Al,front contact,light-scattering,surface texture,light-coupling
更新于2025-09-16 10:30:52
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From normal diffusion to superdiffusion: Photothermal heating of plasmonic core-shell microgels
摘要： The motion of core-shell colloids during laser heating is studied using angle-dependent pump-probe dynamic light scattering. The cores consist of a single spherical gold nanoparticle whose localized surface plasmon resonance has a strong spectral overlap with the wavelength of the pump laser. They are homogeneously encapsulated in thick hydrogel shells composed of either chemically cross-linked poly-N-isopropylacrylamide or poly[2-(2-methoxyethoxy)ethyl methacrylate], both of which exhibit a temperature-dependent volume phase transition. Thus, upon heating beyond the transition temperature, the hydrogel shells shrink. Intensity-time autocorrelation functions are recorded while illuminating the samples with the pump laser and hence heating the gold cores. With increasing laser intensity, the dynamics changes from normal Brownian motion to superdiffusion. Nevertheless, in the high-q limit, the relaxation times can be extracted and used to estimate the temperature increase, which can reach almost 10 K. This causes a significant deswelling of the hydrogel shells, which is also measured.
关键词： temperature-dependent volume phase transition,photothermal heating,dynamic light scattering,superdiffusion,plasmonic core-shell microgels
更新于2025-09-16 10:30:52
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Laser Light Scattering Study on Aggregation of Cellulose Diacetate in Acetone
摘要： We have investigated the properties of cellulose diacetate in solution by using laser light scattering. The cellulose diacetate molecules can form micelles and micellar clusters in acetone besides the individual chains. As the concentration increases, the average hydrodynamic radius (cid:104)Rh(cid:105) linearly increases, whereas the ratio of gyration radius to hydrodynamic radius (cid:104)Rg(cid:105)/(cid:104)Rh(cid:105) linearly decreases. It indicates that the micelles associate and form micellar clusters due to the intermolecular interactions.
关键词： Laser light scattering,Cellulose diacetate,Multi-aggregation form structure
更新于2025-09-16 10:30:52
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An electrically controlled light-scattering device based on liquid crystal/polymer microsphere composites
摘要： There is a widely applied prospect of electrical controlled liquid crystal (LC) light-scattering device. Numerous electrical controlled LC light-scattering technologies have been studied, but each technology has its own shortcomings, such as high driving voltage, high hysteresis, complex electrode structure, and serious heating. In this work, the composite of LC and polymer microspheres are used to fabricate light-scattering devices. This device is operated by the vertical electric field and does not require complex preparation process. LC/polymer microsphere composite has the advantages of low driving voltage and zero hysteresis. The role of microspheres in the composites is to change the size and density of a refractive-index-mismatched micro-domain. The effects of the ratio, particle size, and refractive index of microspheres on the optical characteristics of a composite are studied. The normal directional light transmittance at the transparent state and light-scattering state decreases with an increasing weight ratio of microspheres. The particle size of microspheres has negligible influence on the electro-optical properties of composites when the weight ratio of microspheres is small. The LCs doped with Polymethylsilsesquioxane (PMSQ) microspheres or polymethyl methacrylate (PMMA) microspheres are compared, and the mismatched refractive index and density of micro-domain show the influence on the electro-optical properties of the composites.
关键词： zero hysteresis,electro-optical properties,liquid crystal/polymer microsphere composites,Liquid crystal light-scattering device
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE Eurasia Conference on IOT, Communication and Engineering (ECICE) - Yunlin, Taiwan (2019.10.3-2019.10.6)] 2019 IEEE Eurasia Conference on IOT, Communication and Engineering (ECICE) - Amount and Scattering of Dyes and their Influence on the Photocurrent Enhancement of TiO2 Hierarchically Structured Photoanodes for Dye-Sensitized Solar Cells
摘要： In this study, we prepared and analyzed the properties of hills-like hierarchically structured TiO2 photoanodes for dye-sensitized solar cells (DSSCs). We expected that the presence of appropriately aggregated TiO2 clusters in the photoanode layer would translate in a relatively strong light scattering and dye loading, increasing the photovoltaic efficiency. A detailed light-harvesting study was performed by employing polyvinyl alcohol (PVA) polymers of different molecular weights as binders for the aggregation of the TiO2 nanoparticles (P-25 Degussa). Hence, we obtained a series of TiO2 films presenting a variety of morphologies. Their reflection, as well as the absorbance of the attached dye, the amount of dye loading, and the performance of the fabricated DSSC devices were investigated. Our optimized device presenting a relatively high dye loading and well light harvesting ability, and able to enhance the short-circuit current (Jsc) in the DSSCs by 23%.
关键词： Dye-sensitized solar cell,Hierarchical structure,Light scattering,TiO2 photoanode
更新于2025-09-16 10:30:52
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Dyes Amount and Light Scattering Influence on the Photocurrent Enhancement of Titanium Dioxide Hierarchically Structured Photoanodes for Dye-Sensitized Solar Cells
摘要： In this study, we prepared and analyzed the properties of hill-like hierarchically structured titanium dioxide (TiO2) photoanodes for dye-sensitized solar cells (DSSCs). We expected that the presence of appropriately aggregated TiO2 clusters in the photoanode layer would translate to relatively strong light scattering and dye loading, increasing the photovoltaic efficiency. A detailed light-harvesting study was performed by employing polyvinyl alcohol (PVA) polymers of different molecular weights as binders for the aggregation of the TiO2 nanoparticles (P-25 Degussa). Hence, we obtained a series of TiO2 films, presenting a variety of morphologies. Their reflection, as well as absorbance of light by the attached dye, the amount of dye loading, and the performance of the fabricated DSSC devices were investigated. Our optimized device, with a relatively high dye loading and good light harvesting ability, was able to enhance the short-circuit current (Jsc) in the DSSCs by 23%.
关键词： hierarchical structure,TiO2 photoanode,light scattering,dye-sensitized solar cell
更新于2025-09-16 10:30:52