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Light trapping for photovoltaic cells used for optical power transmission
摘要： Photovoltaic (PV) cells used for optical power transmission convert laser light incident from limited directions to electricity. This illumination condition is in contrast to that for solar cells. A combination of an angular selective filter consisting of a dielectric multilayer on the front surface and a diffuse reflector on the rear surface significantly traps both the incident laser light into and radiation from the PV cell. This light trapping effect can improve the monochromatic conversion efficiency of a GaAs PV cell by 9% (absolute) compared with that for the ×4n2 trapping, under 872 nm and 1 W cm?2 laser illumination.
关键词： GaAs,light trapping,conversion efficiency,optical power transmission,photovoltaic cells
更新于2025-09-23 15:21:01
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Effect of fruit moving speed on online prediction of soluble solids content of apple using Vis/NIR diffuse transmission
摘要： The effect of fruit moving speed on online prediction of soluble solids content (SSC) of “Fuji” apples based on visible and near-infrared (Vis/NIR) spectroscopy was studied. Diffuse transmission spectra between 615 and 1,045 nm were collected with a commercial online system at speeds of 0.3 m/s (S1), 0.5 m/s (S2), and 0.7 m/s (S3). Compensation models for SSC of each speed alone (local models) and all speeds (global model) were established using partial least squares (PLS). For global model, spectra of each sample were divided into three parts (P1, P2, and P3), three kinds of spectra partition combinations (P12, P13, and P23) were established. Results showed that S3 performed better and the influence of speed on spectra greatly affected SSC evaluation accuracy between local models. Comparatively, global model was insensitive to fruit moving speed variation and effective wavelengths (EWs) selected by competitive adaptive reweighted sampling (CARS) after Savitzky–Golay smoothing (SGS) achieved better results than local models. Importantly, 36 EWs selected by CARS after SGS of global-P13 model achieved the best results with rp and RMSEP of 0.8419, 0.8895, 0.8948 and 0.6281, 0.5318, 0.5196(cid:1)Brix, respectively. Generally, global-P13 model with EWs is promisingly applied to online SSC prediction of apple by Vis/NIR diffuse transmission.
关键词： soluble solids content,online prediction,effective wavelengths,competitive adaptive reweighted sampling,partial least squares,fruit moving speed,apple,diffuse transmission,Vis/NIR spectroscopy
更新于2025-09-23 15:21:01
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The Influence of Incident Power on the Magnetic Fluid Sensor Sensitivity Based on Optical Transmission Properties
摘要： Sensitivity is a critical characteristic of sensors, and increasing the sensitivity of the sensor is valuable for measurement study. Incident power has an important influence on the sensitivity of magnetic fluid sensors based on optical transmission properties. Variation in the magnetic field sensitivity at different incident powers was investigated by the measurement of transmitted power through the magnetic fluid sensors. As the magnetic field strength increases, the sensitivity variation of the magnetic fluid film sensor can be divided into four stages: first decreasing sharply, secondly increasing, then decreasing gradually, and finally tending toward a small stable value. The magnitudes of the change in the sensor sensitivity are influenced by the incident power, because the structural pattern of the nano-magnetic particles in the magnetic fluid sensor changes, the Soret effect and the Photonic Hall effect co-define the sensing system. In the weak magnetic field range, when a higher sensitivity is required, it is appropriate to select a larger incident power; however, in a large magnetic field range, when a higher sensitivity is required, a small incident power should be selected. Therefore, the magnetic fluid film sensor exhibits different sensitivity characteristics if different incident power values are chosen. The appropriate incident power can be selected according to the range of the magnetic field to be measured to improve the sensitivity in the magnetic field measurement study.
关键词： sensitivity,magnetic fluid sensor,Photonic Hall effect,incident power,optical transmission properties,Soret effect
更新于2025-09-23 15:21:01
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Tunable graphene-on-insulator band-stop filter at the mid-infrared region
摘要： This paper presents a novel graphene-on-insulator (GOI) band-stop filter in the mid-infrared region. The finite-difference time-domain method is used to model our GOI basic and advanced filters and calculate their transmission spectra for different graphene layers at every gate-source voltage. The numerical results reveal the resonance wavelength, modulation depth, and bandwidth of the advanced filter can be tuned in the range of 11.5 to 30 μm, ?57 to ?60 dB, and 2 to 4 μm, respectively. These results are obtained by variation of the physical parameters, such as the number of overlapped filters, the number of graphene layers, and the applied chemical potential. Our results indicate that the proposed advanced band-stop filter is an excellent device to be used in an ultra-fast active graphene-based plasmonic systems for THz applications.
关键词： Finite-difference time-domain,Graphene-on-insulator,Transmission,Mid-infrared,Band-stop filter
更新于2025-09-23 15:21:01
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A Bi-layered Chiral Metamaterial with High-Performance Broadband Asymmetric Transmission of Linearly Polarized Wave
摘要： In this paper, a novel bi-layered chiral metamaterial (CMM) is presented to realize high–efficiency broadband asymmetric transmission (AT) of linearly polarized electromagnetic wave (EM) in the microwave region from 10.1GHz to 15.1GHz. For this purpose, a pair of modified resonators is employed on two sides of a thin dielectric substrate. The simulated and measured results confirm that linearly polarized wave in the form of x-polarized or y-polarized could be nearly converted into the orthogonal polarization after transmission through the introduced prototype which is affirmed by the polarization rotation azimuth angle . The polarization conversion ratio (PCR) is more than 92% at the mentioned frequency range. Full parametric simulation of modified resonators, azimuth rotation angle, and chirality parameter variable with frequency are discussed in detail. In addition, the surface current distributions of the structure have been demonstrated to investigate the physical mechanism of the cross-polarization and corresponding polarization conversion.
关键词： Metamaterials,chiral metamaterial,linearly polarized wave,asymmetric transmission
更新于2025-09-23 15:21:01
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Kinetics of graphitization of thin diamond-like carbon (DLC) films catalyzed by transition metal
摘要： In this paper, we have studied the kinetics of graphitization at 773K of thin diamond-like carbon (DLC) films coated with minute amount of Ni metallic particles. DLC films are deposited at room temperature by pulsed laser deposition (PLD) on a transparent quartz substrate, and Ni is deposited on the surface of DLC using molecular beam epitaxy technique at room temperature. The ultra-high vacuum thermal (range 573-873K with 60 min annealing treatments) and kinetic (range 30-3760 min at 773K) behaviors of the deposited films are investigated. Surface and interface characterizations indicate that the growth of graphitic sp2 clusters starts at temperatures lower than 573K. The kinetics of graphitization is recorded at 773K. Thus, the continuous growth of graphitic clusters leads to a long-range kinetics. These clusters are responsible for the increase in the electrical conductivity and carrier mobility, reaching values of 6.103 Siemens/cm and 20 V/cm2?s, respectively. This continuous change is not only explained by the nucleation and growth of graphitic clusters, but also by some reorientation of them alongside both the surface and the quartz substrate. The obtained results demonstrate that thermally post-treated catalytic metal/DLC films are promising materials for conductive electrodes and sensing applications.
关键词： Raman spectroscopy,thermal treatment,electric transport measurements,optical transmission and absorption,diamond-like carbon,thin graphite films,pulsed laser deposition,metal catalyst
更新于2025-09-23 15:21:01
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A charge-transfer resistance model and Arrhenius activation analysis for hydrogen ion transmission across single-layer graphene
摘要： Transmission rates for protons and deuterons across single-layer graphene embedded in Nafion | graphene | Nafion sandwich structures are measured as a function of temperature in electrochemical hydrogen pump cells. Rates of ion transmission through graphene are obtained in the form of area-normalized ion-transfer resistances, and are interpreted in terms of ion-exchange current densities and standard heterogeneous ion-transfer rate constants. An encounter pre-equilibrium model for the ion-transfer step is then used to provide rate constants for the fundamental microscopic step of ion (proton or deuteron) transmission across graphene. Application of this rate model to interpret variable-temperature data on proton and deuteron transmission rates provides values for the activation energy and pre-exponential factor for the fundamental ion transmission step across graphene. Activation energies obtained from the Arrhenius plots for proton and deuteron transmission are as follows; for proton, Eact = 48 ± 2 kJ mole-1 (0.50 ± 0.02 eV) and for deuteron, Eact = 53 ± 5 kJ mole-1 (0.55 ± 0.05 eV). The difference between these two values of approximately 5 kJ mole-1 is in good agreement with the expected difference in vibrational zero-point energies for O-H and O-D bonds, albeit with some uncertainty given the uncertainties in the activation energy values. Pre-exponential frequency factor values of 8.3 ± 0.4 x 1013 s-1 and is 4.7 ± 0.5 x 1013 s-1 were obtained for proton and deuteron transmission respectively across graphene. These pre-factor values are both quite large, on the order of the values predicted from the Eyring – Polanyi equation with a transmission coefficient near one. The ratio of 1.8 for the rate pre-factors (H/D) is in reasonable agreement with the value of 1.3 for the ratio of bond vibrational frequencies for O-H and O-D stretching, respectively. Taken together, these data support a model in which proton and deuteron transmission across graphene are largely adiabatic processes for which the differences in transmission rate at room temperature are due largely to differences in activation energies.
关键词： Nafion,proton transmission,Graphene,2D materials,hydrogen pumping
更新于2025-09-23 15:21:01
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Role of Sb on the vertical-alignment of type-II strain-coupled InAs/GaAsSb multi quantum dots structures
摘要： The implementation of GaAs0.8Sb0.2 as CL to obtain type-II strain-coupled InAs MQD structures has been examined and compared to similar structures without Sb or without strain coupling. First, it has been demonstrated that capping with GaAsSb prevents the formation of In-rich agglomerations that hampered the QD formation as it has been observed in the sample without Sb. Instead, it promotes the vertical alignment (VA) of almost all QDs with a high density of QD columns. Second, there is a preferential Sb accumulation over the dots together with an undulation of the growth front, contrary to the observed in the uncoupled structure. In case of a deficient covering of GaAsSb, as occurs for giant QDs, In-rich agglomerations may develop. Each VAQD column consists of a sequence of alternating quantum blocks of pyramid-shaped In(Ga)As separated by GaAsSb blocks that rest over them. These Sb-rich blocks are not homogeneous accumulating around the pyramidal apex like a collar. Between the columns, there is an impoverishment of In and Sb compared to the uncoupled sample. These columns can behave as self-aligned nanowires with type II band alignment between self-assembled InAs and GaAsSb quantum blocks that opens new opportunities for novel devices.
关键词： GaAsSb capping layer,III-V semiconductors alloys,Transmission electron microscopy,Composition distribution,Vertical aligned quantum dots
更新于2025-09-23 15:21:01
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Effect of molecular weight on the feature size in organic ice resists
摘要： The feature size of patterns obtained by electron beam lithography (EBL) depends critically on resist properties, beam parameters, development process, and instrument limitations. Frozen layers of simple organic molecules such as n-alkanes behave as negative tone resists for EBL. With the unique advantage of an in-situ thermal treatment replacing chemical development, the entire lithographic process can be performed within a single instrument, thus removing the influence of chemical developers on the feature size. By using an environmental transmission electron microscope, we can also minimize the influence of instrumental limitations and explore the fundamental link between resist characteristics and feature size. Our results reveal that the onset dose of organic ice resists correlates with the inverse molecular weight, and that in the thermal development the role of change in solubility of polymers is mirrored in a shift in the solid/vapour critical temperature of organic ices. With a 0.4 pA beam current we obtained 4.5 nm, 5.5 nm, 8.5 nm, lines with frozen octane, undecane, and tetradecane, respectively, consistent with the predictions of a model we developed that links beam profile and feature size. The knowledge acquired on the response of small organic molecules to electron irradiation, combined with the flexibility and operational advantages of using them as qualified EBL resists, provide us with new opportunities for the design and production of nanodevices, and broadens the reach of EBL especially towards biological applications.
关键词： crosslinking,exposure mechanism,organic ice resist,transmission electron microscopy,E-beam lithography,condensed organic molecules
更新于2025-09-23 15:21:01
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Photonic transmission spectra in graphene-based Gaussian random multilayers
摘要： The light-matter interaction is a very active and attractive research field and it is the basis of the photonic devices based on the generation, processing and storage of photons. In this work, we theoretically study the propagation of electromagnetic waves in one-dimensional photonic crystals consisting of two different dielectric slabs (silicon dioxide and titanium dioxide) separated by graphene. The spatial arrangement of the slabs is periodic, but we introduce randomness by using a Gaussian distribution of thickness with a specific standard deviation σ. The well-known transfer-matrix method is used as the mathematical approach. Our main goals are to investigate how the presence of such randomness can change the light transmission spectra and the emergence of robust photonic band gaps. For a given angle of incidence, our numerical results show that the two lowest frequency bandgaps are insensitive to the influence of the Gaussian distribution. Those band gaps emerge from two different mechanisms: one is due to the presence of graphene, while the other is due to the Bragg’s scattering. A strong transmission dependence on the standard deviation σ is also observed in our numerical results. More interesting, for the transversal magnetic case (angle of incidence θ ? 60°) the system can be adjusted to present transmission coefficient near to 1 and work like a perfect transparent media, what is useful for technological applications.
关键词： Electromagnetic waves propagation,Light waves transmission,Graphene,Photonic crystals,Random multilayers
更新于2025-09-23 15:21:01