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Effect of nanoparticle size to improvement in absorption in Plasmonic solar cell
摘要： In last decades, plasmonics gives very high attention and closely involves in the main domains of nanophotonics which can control of optical fields at the nanodimension level. Its most striking property is to concentrate and enhance the electromagnetic field on the nanometer scale especially in solar cell. In plasmonic field, Nobel metals used as nanoparticle where density of electron gas which oscillates at surface plasmon frequency at the same time also improves absorption by scattering. So the use of plasmonic in solar cell gives better opportunity to enhance efficiency by absorption as the optical spectrum loss are most part of total loss in solar cell. In this paper, we investigate the effect of nanoparticle dimension for enhancement of extinction in terms of absorption and scattering by means of surface plasmon and also studied finite-difference time domain based proposed model which shows improvement in various simulated surface plasmonic fields components.
关键词： extinction,absorption,polarizability,plasmonics,finite difference time domain,scattering,surface Plasmon polariton
更新于2025-09-16 10:30:52
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Scattering metal waveguide based speckle-enhanced prism spectrometry
摘要： As children develop, they differ from adults in a number of important ways, including anatomy, metabolism, immune system, and the extent of myelination of the nervous system. As a consequence, equivalent exposures to radiation from mobile phones result in different doses to specific tissues in children compared with adults. Higher doses are likely to have more severe implications in the young. A young child’s skull is not only smaller and thinner than an adult’s, but also has dielectric characteristics closer to those of soft tissues, probably due to a higher water content. The young skull better matches the electromagnetic characteristics of the skin and brain. As a result, finite-difference time-domain (FDTD) simulations confirm field penetration and higher specific absorption rate (SAR) in deeper structures in the young brain. If the peak spatial SAR (psSAR) is modeled in the entire head, as current testing standards recommend, the results for adults and children are equivalent. Our anatomically based evaluations rely on FDTD simulations of different tissues within the brain and confirm that the psSAR in a child’s brain is higher than in an adult’s brain.
关键词： dosimetry,mobile phone certification,finite-difference time-domain simulation,Specific absorption rate
更新于2025-09-16 10:30:52
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Tunable plasmonic absorber in THz-band range based on graphene “arrow” shaped metamaterial
摘要： A tunable selective absorber consisting of a periodic “arrow” shaped graphene array that operates in the far infrared and terahertz range is proposed. It is achieved by depositing a set of graphene “arrow” shaped ribbon on a SiO2 dielectric spacer layer. The absorption characteristics of the structure are investigated by the Finite Difference Time Domain (FDTD) method. The results show that the maximum pure absorption rate at the resonant wavelength increases from 1.09% corresponding to Fermi energy level 0.2 eV to 12.76% corresponding to 0.8 eV, which is improved by nearly 12 times. Moreover, the relaxation time is increased from 0.1 ps to 1.0 ps with the other parameters are unchanged, and the maximum value of the pure graphene absorption peak increases from 1.62% to 11.55%. Moreover, the resonance wavelengths of the absorber possess angle insensitivity, nevertheless the absorption peak intensity is sensitive to the angle of incidence. In addition, this paper also compares the double-symmetric “arrow” shaped structure on the basis of this structure. The absorption spectrum of the structure shows a double peak phenomenon, which can achieve the purpose of selective absorption. The research results have certain guiding significance and important reference value for the design of next–generation graphene-based perfect terahertz absorbers, and the design can be applied to the fields of label-free biomedical sensing, photodetectors and photonic devices.
关键词： Absorber,Finite Difference Time Domain method,Surface plasmon,Graphene,Metamaterial
更新于2025-09-12 10:27:22
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Optimization of MAPbI$_3$-Based Perovskite Solar Cell With Textured Surface
摘要： In this article, the optimized condition for a perovskite solar cell (PSC) with textured surface has been calculated. To accurately model the transport in organic material and organic/inorganic interface, the Gaussian-like density of state function was utilized into Poisson and drift-diffusion solver to present the tail states in the organic material. To calibrate the simulation model, the planar structures with published experimental results are compared. Our results show that the textured structure can improve the open-circuit voltage (Voc) and fill factor and overcome the major problem of PSC because of the short diffusion length. Finally, the efficiency has been improved from 17.8% (planar) to 20.8% (textured). If the metal contact with a suitable work function is chosen, it can be further improved to 22.9%.
关键词： perovskite solar cell (PSC),organic material,MAPbI3,Poisson equation,Drift-diffusion equation,2-D finite-difference time domain (FD-TD),tail states model
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - THz Time-Domain Reflection Spectroscopy of KTiOPO <sub/>4</sub>
摘要： Terahertz (THz) radiation has been of increasing interest in the last decades, for security, manufacturing, quality control, medical and security imaging applications. The field requires more efficient and affordable sources and nonlinear upconversion schemes point in this direction. KTiOPO, (KTP) is a well-established material for nonlinear optical applications in the visible and near-IR region thanks to its large transparency, high nonlinear coefficient and damage threshold. Its reasonably low absorption [1, 2] and strong polariton resonances [1] show promise for efficient IR to THz upconversion and Wu et al. [2] recently demonstrated its superiority to LiNbO3 and LiTaO3 in a back to back experiment. However, the complex refractive index needs to be measured before further power scaling is realistic. Terahertz time-domain spectroscopy (TTDS) allows for direct extraction of both the phase and amplitude of the THz electric field and grants the possibility of extracting the optical parameters n and α. In this work, we report on THz time-domain reflection spectroscopy of flux grown KTP from 0.5 to 7 THz at room temperature. The THz-TDS setup used air-filament plasma for generation of the THz radiation and the Pockel's effect in 300um thick GaP for detection. The a and b-axis of a KTP crystal were probed using an HDPE polarizer and rotation of the sample. The geometry of the setup is based on the work of Pashkin et al. [3], where the THz was focused onto the GaP crystal after the 25x15x0.5mm3 sample. Fig.1 shows the refractive index and the absorption coefficient from left to right, respectively. Blue and red color depict the two axes of the KTP crystal. Errors are estimated to: ?n < ±0.025 and ?α <±5 cm?1 (0.5?3THz), ?n < ±0.05 and ?α < ±25 cm?1 (3?5THz), ?n < ±0.1 and ?α < ±50 cm?1 (5?6THz), ?n < ± 0.25 and ?α < ±150 cm?1 (6?7THz). The accuracy in frequency was ≈ 90 GHz or 2 cm?1, limited by the scan time of 11ps. To the best of our knowledge, the convoluted frequency dependent nature of the refractive index has not been measured by direct time-resolved THz measurement before. Earlier spectroscopic studies of KTP have either lacked the possibility of directly extracting the complex refractive index [4] or been limited by absorption of the transmitted signal due to the strong resonances of KTP, limiting the bandwidth to about 2.5 THz [5]. In the regions where the bandwidth of this and older studies overlap, the measurements are similar, giving credibility to both measurements over the whole bandwidth. Besides, the measured resonances in Fig.1 can be related to IR active phonon modes, as seen in, e.g. [6]. This study will be of utmost importance when constructing new devices for optical to THz conversion. We also report a possible new phonon mode at 1.4 THz.
关键词： absorption coefficient,KTiOPO4,refractive index,THz time-domain spectroscopy,Terahertz
更新于2025-09-12 10:27:22
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Eliminating Phase Drift for Distributed Optical Fiber Acoustic Sensing System with Empirical Mode Decomposition
摘要： Phase-drift elimination is crucial to vibration recovery in the coherent detection phase-sensitive optical time domain re?ectometry system. The phase drift drives the whole phase signal ?uctuation as a baseline, and its negative e?ect is obvious when the detection time is long. In this paper, empirical mode decomposition (EMD) is presented to extract and eliminate the phase drift adaptively. It decomposes the signal by utilizing the characteristic time scale of the data, and the baseline is eventually obtained. It is validated by theory and experiment that the phase drift deteriorates seriously when the length of the vibration region increases. In an experiment, the phase drift was eliminated under the conditions of di?erent vibration frequencies of 1 Hz, 5 Hz, and 10 Hz. The phase drift was also eliminated with di?erent vibration intensities. Furthermore, the linear relationship between phase and vibration intensity is demonstrated with a correlation coe?cient of 99.99%. The vibrations at 0.5 Hz and 0.3 Hz were detected with signal-to-noise ratios (SNRs) of 55.58 dB and 64.44 dB. With this method, when the vibration frequency is at the level of Hz or sub-Hz, the phase drift can be eliminated. This contributes to the detection and recovery of low-frequency perturbation events in practical applications.
关键词： phase drift elimination,phase recovery,phase-sensitive optical time domain re?ectometry,distributed acoustic sensing system,empirical mode decomposition
更新于2025-09-12 10:27:22
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[IEEE 2019 International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET) - Istanbul, Turkey (2019.8.26-2019.8.27)] 2019 International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET) - Simulation of Solar Cell Absorption Enhancement via Incorporation of Plasmonic Nanoparticles
摘要： Among the various technologies available for solar energy generation, photovoltaics has a unique advantage due to the ease of use, effectiveness and prevalent availability of solar energy. Solar cell efficiency is key to the widespread use of photovoltaic technology for power generation. Absorption of photons within the active media is one such pre requisite to increasing the optical generation rate and thus electron-hole generation. Plasmonics – the study and manipulation of coupled electron-photon oscillations – provides a gateway towards fulfilling this need. In this study, we make use of the inherent loss of localized surface plasmon resonance (LSPR) into the dielectric media. To demonstrate this, we evaluate the increase in optical absorption as a function of nanoparticle radius in a silver nanosphere lattice. Discussion is presented on the role of the electric field and on the underlying mechanisms.
关键词： Photovoltaics,Finite-difference,Nanotechnology,Absorption enhancement,Plasmonics,Time domain simulation,Localized surface plasmon resonance
更新于2025-09-12 10:27:22
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Finite difference time domain simulation of arbitrary shapes quantum dots
摘要： Utilizing the finite difference time domain (FDTD) method, energy eigenvalues of spherical, cylindrical, pyramidal and cone-like quantum dots are calculated. To do this, by the imaginary time transformation, we transform the schr?dinger equation into a diffusion equation. Then, the FDTD algorithm is hired to solve this equation. We calculate four lowest energy eigenvalues of these QDs and then compared the simulation results with analytical ones. Our results clearly show that simulation results are in very good agreement with analytical results. Therefore, we can use the FDTD method to find accurate results for the Schr?dinger equation.
关键词： Finite difference time domain,Quantum dots,Energy eigenvalues,Schr?dinger equation
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Common Pulse Retrieval Algorithm: A Fast and Universal Method to Retrieve Ultrashort Pulses
摘要： Measuring the temporal shape of ultrashort laser pulses is an important standard task in ultrafast optics. A multitude of methods has been devised for that purpose [1]. However, in many cases a specific, iterative algorithm has to be applied to retrieve the pulse shape from the measurement. In this work we present a common pulse retrieval algorithm (COPRA) that can be universally applied to such pulse measurement methods and compares favorably in terms of speed and accuracy to existing approaches [2]. For example, COPRA can be applied to the well-established frequency-resolved optical gating (FROG) [3], as well as, more recent techniques, such as dispersion scan (d-scan) [4] or time-domain ptychography (TDP) [5] (see Fig. 1). Generally, it is designed for a broad class of measurements where sets of pulse spectra after a nonlinear process such as second-harmonic generation (SHG) or third-harmonic generation (THG) are measured. Specifically, the measurement process has to be tunable by some parameter δ that forms the second measurement dimension. We call this class of measurements parametrized nonlinear process spectra (PNPS). COPRA now finds the pulse spectrum ?E(ω) that matches best to a PNPS measurement T meas(ω, δ ) in the least-squares sense. It does so in two stages: first the local iteration subsequently optimizes ?E(ω) with respect to single spectra, then the global iteration optimizes ?E(ω) with respect to the entire measurement. COPRA usually finds a least-squares solution to the pulse retrieval problem within a few hundreds iterations, i.e., within few tens of seconds on a standard workstation for usual measurement dimensions. This compares very favorably to existing approaches. Additionally, the retrieved pulses are more robust in the presence of Gaussian measurement noise than those retrieved by generalized projections or ptychography. Many existing pulse measurement schemes can directly benefit from COPRA for more robust and faster retrieval. Also, the framework of PNPS measurements may allow to gain more insight on fundamental questions of pulse measurement, will make measurement schemes more comparable and may lead to new and improved methods.
关键词： time-domain ptychography,pulse retrieval,frequency-resolved optical gating,dispersion scan,ultrashort pulses
更新于2025-09-12 10:27:22
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A 2?×?1 all-optical multiplexer using Kerr nonlinear nano-plasmonic switch
摘要： In this paper, a novel surface plasmon polariton based 2 × 1 multiplexer, which is based on an adder module and an all-optical controllable nano-plasmonic switching module is presented. It is shown that by applying a pump light, the transmissions of the input signals into the output waveguide can be controlled. The operation of the proposed device is investigated through the use of coupled-mode theory and finite-difference time-domain method. In the proposed adder module, the transmissions of the input signals at the working wavelengths are about 0.7. Based on the simulation results, by applying a pump light intensity of 150 KW/cm2 the transmissions of input signals alter with the extinction ratio of 22.04 dB, which shows a significant switching effect. For a pump light intensity of 150 KW/cm2 the switching times of input signals are measured about 560 fs. It is expected that the proposed 2 × 1 multiplexer can be used in all-optical signal processing, nano-plasmonic circuits, communication, etc.
关键词： Coupled-mode theory (CMT),Kerr nonlinearity,Racetrack-shaped ring resonator,Finite-difference time-domain (FDTD),Nano-plasmonic switch,All-optical multiplexer
更新于2025-09-12 10:27:22