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Generation of plasmonic hot carriers from d-bands in metallic nanoparticles
摘要： We present an approach to master the well-known challenge of calculating the contribution of d-bands to plasmon-induced hot carrier rates in metallic nanoparticles. We generalize the widely used spherical well model for the nanoparticle wavefunctions to flat d-bands using the envelope function technique. Using Fermi’s golden rule, we calculate the generation rates of hot carriers after the decay of the plasmon due to transitions either from a d-band state to an sp-band state or from an sp-band state to another sp-band state. We apply this formalism to spherical silver nanoparticles with radii up to 20 nm and also study the dependence of hot carrier rates on the energy of the d-bands. We find that for nanoparticles with a radius less than 2.5 nm, sp-band state to sp-band state transitions dominate hot carrier production, while d-band state to sp-band state transitions give the largest contribution for larger nanoparticles.
关键词： Fermi’s golden rule,plasmonic hot carriers,spherical well model,silver nanoparticles,d-bands,metallic nanoparticles,envelope function technique
更新于2025-09-23 15:19:57
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The effect of different obturation methods on sealer penetration alongside apically separated rotary nickela??titanium instruments: A confocal laser scanning microscopy study
摘要： The effects of different obturation techniques on calcium silicate-based sealer penetration in the presence of apically separated rotary files were evaluated. Forty-eight extracted mandibular incisors were used. ProTaper F2 rotary files were separated at the apical thirds. Samples were divided into four groups (n = 12) according to obturation technique used: (a) cold lateral compaction (CLC); (b) single cone; (c) bulk-fill (BF) without a core material; and (d) thermoplastic injection (TI). Specimens were sectioned horizontally at 1 and 3 mm from the apex and studied using a confocal scanning laser microscope. The maximum tubule penetration depth and percentage of penetration were measured. Data were statistically analyzed using parametric and nonparametric tests with a significance level of 5%. Regarding penetration depth, a significant difference was found at 1 mm (p < .05), while no significant difference was found at 3 mm (p > .05). At the 3 mm level, all of the obturation techniques showed similar penetration depths. Regarding penetration percentage, the values of the CLC and TI groups were statistically less when compared with the BF group at 1 and 3 mm levels, respectively (p < .05). Under the limitations of this in vitro study, results suggest that the obturation technique may present a significant effect on sealer penetration.
关键词： sealer penetration,separated instruments,obturation technique,confocal laser scanning microscope
更新于2025-09-23 15:19:57
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Research on velocity measurement of hypersonic turbulent boundary layer based on nano-tracer-based planar laser scattering technique
摘要： With the flight speed of the aircraft increasing, hypersonic aerodynamics has become one of the hot spots in the field of aerodynamics. As one of the most typical flow structures in hypersonic flow, the hypersonic turbulent boundary layer (TBL) is of great significance to optimize the aerodynamic configuration design of a hypersonic vehicle. At the same time, flow information measurement of hypersonic TBLs will not only help us understand the mechanism of hypersonic TBL, but also provide sufficient calibration datum for numerical simulation.
关键词： SIFT (scale invariant feature transformation),NPLS technique,Velocity measurement,Hypersonic turbulent boundary layer
更新于2025-09-23 15:19:57
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Giant Ultrafast Optical Nonlinearities of Annealed Sb2Te3 Layers
摘要： The optimization of thin Sb2Te3 films in order to obtain giant ultrafast optical nonlinearities is reported. The ultrafast nonlinearities of the thin film layers are studied by the Z-scan technique. Giant saturable absorption is obtained, which is the highest ever reported, by means of the Z-scan technique.
关键词： Sb2Te3,Z-scan technique,ultrafast optical nonlinearities,saturable absorption
更新于2025-09-23 15:19:57
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Flap Sliding Technique for Managing Flap Striae following Laser In Situ Keratomileusis
摘要： Purpose. To assess the e?cacy and safety of a simple, noninvasive, “?ap-sliding” technique for managing ?ap striae following laser in situ keratomileusis (LASIK). Methods. This prospective, interventional study included eyes with post-LASIK ?ap striae. All eyes underwent ?ap sliding 1-2 days after surgery. Following ?ap edge epithelialisation, a cellulose sponge was used to gently slide the ?ap perpendicular to the striae direction. This technique allows for ?ap striae treatment without ?ap lifting, avoiding any associated lifting complications. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and refractive error were monitored one day after the ?ap-sliding procedure. Results. Fifteen eyes (15 patients) with post-LASIK ?ap striae were managed using the ?ap-sliding technique. The procedure did not successfully relocate the ?ap striae in 1 eye, and ?ap elevation and ?oating (using a balanced salt solution) were required. Therefore, 14 eyes were included in post-?ap-sliding analyses. The UDVA improved in all patients the ?rst day after the ?ap-sliding procedure was performed, with 11 of 14 eyes (78.57%) reaching an UDVA of 20/25 or better. Complications following ?ap sliding occurred in 2 eyes (14.29%). One eye had intra- operative epithelial abrasion, and 1 eye had residual postoperative striae outside of the optical zone. Conclusion. The ?ap-sliding technique is a simple, noninvasive, e?cient, and safe technique for managing post-LASIK ?ap striae that develop after epithelial healing in the early post-LASIK period. This trial is registered with NCT04055337.
关键词： flap striae,flap-sliding technique,LASIK,corneal refractive surgery
更新于2025-09-23 15:19:57
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Controlled optoelectronic properties and abrupt change in photosensitivity by suppressing density of oxygen vacancies in SnO <sub/>2</sub> nanocrystalline thin films prepared at various spray-deposition temperatures
摘要： Nanostructured SnO2 thin films were synthesized at various substrate temperatures using a modified chemical spray pyrolysis (MCSP) technique. The x-ray diffraction (XRD) patterns confirmed the presence of a rutile SnO2 with tetragonal structure for all the resultant film samples. The XRD results ascertained increase in the grain growth rate and consequent enhancement in crystallinity with increasing the spray-deposition temperature. The optical spectroscopic analysis revealed a significant increase in the optical transmission within the visible region as well as a considerable increase in the optical bandgap by increasing the deposition temperature. However, the spectral distribution of the absorption coefficient ascertained the dominance of direct allowed transition for the SnO2 film samples. The analysis of the current-voltage characteristic curves revealed that the variation of the spray-deposition temperature strongly influences the photosensitivity of the film samples. Based on the electrical results, these film samples reveal a semiconductor behaviour of the transport property over the entire investigated range of the working temperature, with two different conduction mechanisms. The optical and electrical results were combined to evaluate the influence of varying the deposition temperature on the figure of merit (FOM) factor for the SnO2 film samples.
关键词： MCSP technique,optical spectroscopic analysis,electrical transport properties,figure of merit,structural properties,spray deposition temperature
更新于2025-09-23 15:19:57
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Construction of Cr2O3:ZnO Nanostructured Thin Film Prepared by Pulsed Laser Deposition Technique for NO2 Gas Sensor
摘要： Rhombohedral structure of chromium oxide (Cr2O3) thin-film doped hexagonal zinc oxide (ZnO) nanoparticles have been prepared using pulsed laser deposition technique at a different weight percent of ZnO from 0 to 9 wt%. The results of X-ray diffraction analysis shown that the doped films are polycrystalline, and the average crystallite size of the synthesized thin films is found to be dependent on the ZnO concentration. The surface morphology of the prepared thin films was characterized by atomic force microscopy. The optical properties are investigated using ultraviolet–visible light (UV–Vis) absorption spectroscopy. The optical bandgap ranged from 2.45 to 2.68 eV, showing the shift towards longer-wavelength compared to bulk Cr2O3 (~ 3 eV). The sensitivity, response, and recovery times of the sensor towards nitrogen dioxide (NO2) gas were studied and discussed. The sensitivity increase with increasing the doping concentration, and started to decrease when ZnO concentrations reach 7 wt%. The optimal ZnO concentrations for NO2 gas sensitivity is 5 wt%, which attain maximum sensitivity of 87.5% at temperature of 523 K.
关键词： Cr2O3:ZnO nanostructure,Structural properties,Optical properties,Gas sensitivity,PLD technique
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - The Autoconvolution Method Use for Positioning Photonic Crystal Fibers
摘要： In this paper, the autoconvolution method was investigated to determine the position of the longitudinal axis of the photonic crystal fiber and to determine the center of the mode field in the cross section. Knowing the center of the PCF mode field, one can determine the cross section in which the diameter of the mode field will be maximal. This allows a more precise positioning of two identical PCF during connection. The proposed method allows improving the quality of the positioning of the PCF by transverse, angular, longitudinal displacements, and also by the mutual angle of rotation of the connected PCFs.
关键词： optical fibers control,optical power loss,photonic crystal fiber,optical fiber connection,autoconvolution method,mode field,near-field technique
更新于2025-09-23 15:19:57
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - A Frequency Hopping Communication System Using Directly Modulated Laser Based Optical Heterodyne Technique
摘要： This paper proposes a Frequency Hopping (FH) communication system with a novel frequency synthesis method. Considering that the existing frequency synthesis methods are inevitably limited by the electronic device bandwidth, a combination of directly modulated laser (DML) and optical heterodyne technique is proposed as a hopping frequency source. The principle of the method is presented and a dual frequency hopping system in E band is carried out through simulation to veri?ed the feasibility of the proposed method. This frequency synthesis method supports high radio frequency, ultra-wideband and high hopping speed.
关键词： Directly Modulated Laser,E band,Optical Heterodyne Technique,Frequency Hopping,Frequency Synthesis
更新于2025-09-23 15:19:57
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Sending-or-Not-Sending with Independent Lasers: Secure Twin-Field Quantum Key Distribution over 509??km
摘要： Twin-field (TF) quantum key distribution (QKD) promises high key rates over long distances to beat the rate-distance limit. Here, applying the sending-or-not-sending TF QKD protocol, we experimentally demonstrate a secure key distribution that breaks the absolute key-rate limit of repeaterless QKD over a 509-km-long ultralow loss optical fiber. Two independent lasers are used as sources with remote-frequency-locking technique over the 500-km fiber distance. Practical optical fibers are used as the optical path with appropriate noise filtering; and finite-key effects are considered in the key-rate analysis. The secure key rate obtained at 509 km is more than seven times higher than the relative bound of repeaterless QKD for the same detection loss. The achieved secure key rate is also higher than that of a traditional QKD protocol running with a perfect repeaterless QKD device, even for an infinite number of sent pulses. Our result shows that the protocol and technologies applied in this experiment enable TF QKD to achieve a high secure key rate over a long distribution distance, and is therefore practically useful for field implementation of intercity QKD.
关键词： remote-frequency-locking technique,repeaterless QKD,ultralow loss optical fiber,secure key distribution,Twin-field quantum key distribution
更新于2025-09-23 15:19:57