Floriana Morabito, Daniela Fontani, Paola Sansoni
et al.
The exploitation of bifacial solar cells in photovoltaics aims to provide cost-effective solutions to maximize solar power collection on specific surfaces. A prerequisite for this is the effective collection of backscattered diffuse light from albedo, to which self-shading is an obstacle. We discuss the benefits of bifaciality for an asymmetric low-concentrating and spectral-splitting photovoltaic optics system that features a wedged right-prism geometry to address self-shading. The performance of the conceptual design is analyzed, using commercial ray-tracing software, for four different latitudes of installation, by assuming a standard solar AM1.5G spectrum as input. The daily Relative Optical Power Increase (ROPI) is evaluated with respect to standard flat bifacial configurations, reaching ROPI = 293% at a latitude of 25° north at winter solstice. The photocurrent and total Power Conversion Efficiency (PCE) in a four-terminal (4T) configuration are estimated, assuming the operation of a commercial Si HJT bifacial cell and a commercial single-junction GaAs cell. A global increase in PCE of up to 23% is obtained with respect to the best-performing trackless standard bifacial configuration. From this perspective, the use of high-performance, high-bandgap solar cells in 4T configurations might further leverage the advantages of the optics proposed here.
Alagu Vibisha G, Senthilkumar V, Priyadharsini N
et al.
This numerical work focuses on the excellent performance of urine glucose level detection under a SPR-based sensing technology. The low-cost plasmonic metal Al based hybrid structure (Al-bimetal-PbTiO3-BlueP/WS2) is suggested for the modified Kretschmann design, which is found to offer accurate glucose detection along with reduced sensor fabrication cost. The bimetallic combination of Co, Ni, and Pt along with Al thin film is suggested to inhibit the oxidation of Al and numerically optimized for enhance sensing performance. The inclusion of 2D material such as a BlueP/WS2 as a suitable cover layer is found not only to protect the sensor but also to provide good interaction with the sensing medium to increase sensor sensing functionality. Results shows upon suitably optimizing each layer thickness enhanced sensitivity as high as 321°/RIU, 326.8°/RIU, 349.6°/RIU, 380.26°/RIU, and 525.48°/RIU for the glucose concentrations of 0.625 g/dL, 1.25 g/dL, 2.5 g/dL, 5 g/dL, and 10 g/dL, respectively. This simplified configuration and high sensitivity make it quite suitable for obtaining a more accurate identification of urine glucose levels.
Here, a spectrally selective solar absorber is explored and an ultra‐broadband solar absorber is proposed based on pyramidal structure. The finite‐difference in time domain (FDTD) software is used to model the spectral characteristics and magnetic absorption patterns of this absorber. The emissivity of the absorber is less than 20% in the far‐infrared band over 6000 nm, showing good selectivity, and the total solar thermal conversion efficiency is very close to that of an ideal truncated selective solar absorber by analyzing the performance of our proposed absorber‐related indexes. By studying the high absorption band of the absorber, the selectivity can be better investigated in depth. Here, 200–4000 nm is chosed as the depth study band. The absorber possesses an ultra‐wide bandwidth of 3554 nm and an average absorption of over 97.4%, and in the 200–3754 nm band, the absorber has an ultra‐high absorption rate of more than 98.3%, and its thermal emitter has a high emission efficiency of 94% at a temperature of 1000 K. Notably, the weighted average absorption in the 280–4000 nm band at AM1.5 is as high as 98.86%, with a loss of only 1.14%. The ultra‐broadband absorption property of this solar absorber is mainly a joint effect of surface plasmon resonance coupling.
When using underwater optical wireless communication in areas close to human habitats— such as shallow sea areas—specifications for highly-secure, large-capacity optical transceivers are required. Real-time transmission of 850 nm, direct-current optical orthogonal frequency division multiplexing signals for full-duplex underwater invisible light communication has been achieved. We experimentally confirmed that subcarrier adaptive modulation could transmit at maximum capacity depending on the transmission distance, while changing the transmission distance in shallow seawater channels. We confirmed that there was no disturbing influence due to sunlight by using a honeycomb structure for sunlight shielding. Moreover, we found that the effect of disruption caused by the sea surface vibrating due to the 3 m/s wind speed did not affect the signal quality. 4K video streaming is also done on a 1.2 m underwater channel transmission. To the best of our knowledge, this is the first report of full-duplex transmission of invisible-band underwater optical wireless communication for shallow waters.
This article presents a novel approach to investigating a reconfigurable Dielectric Resonator antenna using Graphene Nano Ribbon (GNR) in the terahertz band. Two Elliptical shape DRAs are merged to realize High gain and radiation efficiency. The Roger-6010 is utilized to construct an Elliptical shape Dielectric Resonator (EDRA), and GNR structures are constructed on top of it to achieve reconfigurability. The radiation performance of projected EDRA is investigated in terms of 10 dB Impedance bandwidth, reflection coefficient, surface current, directivity, radiation efficiency, and gain in the frequency range from 0.55-to-0.75-THz. The proposed EDRA design has an impedance bandwidth of 15.64 %, a peak gain of 11.9dBi, peak directivity of 13.1dBi, and radiation efficiency of 97.3 %. Moreover, the reconfigurability nature is investigated by the chemical potential of the surface conductivity of graphene and then GNR-based EDRA radiation parameters. The projected EDRA is suitable for various applications in the THz band.
Daniel T. Cassidy, Jean-Pierre Landesman, Merwan Mokhtari
et al.
Measurements of the cathodoluminescence (CL) and the degree of polarization (DOP) of (CL) from the facet of a GaAs substrate and in the vicinity of a SiN stripe are reported and analyzed. The deformation induced by the SiN stripe is estimated by fitting the measured DOP to 3D finite element method (FEM) simulations. The deformation is found to be more complex than an initial condition of biaxial stress in the SiN. A ratio of fit coefficients suggests that the dependence of DOP on strain is described by equations presented in Appl. Opt. 59, 5506–5520 (2020). These equations give a DOP that is either proportional to a weighted difference of the principal components of strain in the measurement plane, or proportional to the shear strain in the measurement plane, depending on the chosen orientation of the measurement axes.
In this paper, the incident beam called high-dimensional circular hollow sinh-Gaussian (HD-CHsG) beam with a novel wavefront is proposed, which is determined by three parameters (<italic>m</italic>, <italic>σ</italic><sub>0</sub>, <italic>σ</italic><sub>1</sub>). Based on the Richards-wolf vector diffraction theory, it can be focused into a longitudinal polarized optical needle through a high numerical aperture lens. The effects of the three parameters (<italic>m</italic>, <italic>σ</italic><sub>0</sub>, <italic>σ</italic><sub>1</sub>) on the resolution and depth of focus of the longitudinally polarized optical needle are simulated and analyzed. In the condition of (<italic>m</italic>, <italic>σ</italic><sub>0</sub>, <italic>σ</italic><sub>1</sub>) = (8, 0.6, 0.125), a super-diffraction longitudinal optical needle with ultra-long focal depth (resolution 0.40<italic>λ</italic>, focal depth 18.36<italic>λ</italic>, depth-to-width ratio 45.9:1) is generated. In addition, compared with a radially polarized incident beam whose amplitude distribution is Gaussian and circular hollow sinh-Gaussian (CHsG) distribution, the resolution and depth of focus of the longitudinally polarized optical needle obtained by focusing the HD-CHsG beam are higher. Both simulations and experiments are carried out to demonstrate the availability of our method. Our findings are of great significance to the production, manipulation, and application of longitudinally polarized optical needle.
Fast active quenching of single-photon avalanche diodes (SPADs) is important to reduce the afterpulsing probability (APP). An option to reduce the reaction time of electronics to a SPAD's avalanche is to design a quencher exploiting bipolar transistors. A quencher in a 0.35 μm CMOS technology with a nominal supply voltage of 3.3 V, which operated with excess bias voltages up to 6.6 V, was re-designed accordingly. In the new 0.35 μm pure-silicon BiCMOS quencher, the comparator takes advantage of a bipolar differential amplifier, which additionally gives the head room to increase the width of some CMOS transistors as well. The proposed BiCMOS quencher is able to drive the load of a wire-bonded 184 μm-diameter SPAD, while the CMOS design fails. A comparison, where both chips are measured with a wire-bonded, 34 μm-diameter SPAD, shows that the BiCMOS quencher has a reaction time, which is 330 ps to 1.1 ns faster than that of the CMOS quencher.
Kae Lin Wong, Sharon Xiaodai Lim, Zheng Zhang
et al.
The feasibility of laser‐engineered fluorescence emission from carbon black (CB) with three laser sources of different wavelengths—660 nm (red), 532 nm (green), and 405 nm (blue) is demonstrated. From which the 660 nm focused laser beam produces the most intense fluorescence. Detailed systematic studies on how the laser‐engineered fluorescence emission from CB depends on laser power, laser patterning speed, and environmental control during the laser modification process are carried out. From the systematic studies, the CB samples in ambience undergo most noticeable modifications with a laser power of ≈7 mW and patterning speed of ≈12 μms−1. The fluorescence emission is attributed to the creation of complex defects states into the oxidized form of the pristine system by the formation of 1) C60 fullerene and fullerites; 2) ZnO; 3) Zn2SiO4, and more complex hybrid such as 4) carbon‐induced mid‐gap states in Zn2SiO4, and 5) Ca‐induced defects in ZnO. Such incorporations resulted in the formation of intermediate states in the large bandgap materials. As a result, distinct multicolored fluorescence is emitted by these laser‐quenched material systems. Accordingly, multicolored fluorescence designs can be created with elaborative control of focused laser treatment in an ambient and helium environment.
High-resolution addressing of individual ultracold atoms, trapped ions or solid state emitters allows for exquisite control in quantum optics experiments. This becomes possible through large aperture magnifying optics that project microscopic light patterns with diffraction limited performance. We use programmable amplitude holograms generated on a digital micromirror device to create arbitrary microscopic beam shapes with full phase and amplitude control. The system self-corrects for aberrations of up to several λ and reduces them to λ/50, leading to light patterns with a precision on the 10-4 level. We demonstrate aberration-compensated beam shaping in an optical lattice experiment and perform single-site addressing in a quantum gas microscope for 87Rb.
A fiber nonlinearity compensation scheme based on a complex-valued dimension-reduced neural network is proposed. The proposed scheme performs all calculations in complex values and employs a dimension-reduced triplet feature vector to reduce the size of the input layer. Simulation and experiment results show that the proposed neural network needed only 20% of computational complexity to reach the saturated performance gain of the real-valued triplet-input neural network, and had a similar saturated gain to the one-step-per-span digital backpropagation. In addition, the proposed scheme was 1.7 dB more robust to the noise from training data and required less bit precision for quantizing trained weights, compared with the real-valued triplet-input neural network.
The response of fiber specklegram sensors (FSSs) is given as function of variations in the intensity distribution of the modal interference pattern or speckle pattern induced by external disturbances. In the present work, the behavior of a FSS sensing scheme under thermal perturbations is studied by means of computational simulations of the speckle patterns. These simulations are generated by applying the finite element method (FEM) to the modal interference in optical fibers as a function of the thermal disturbance and the length of the sensing zone. A correlation analysis is performed on the images generated in the simulations to evaluate the dependence between the changes in the speckle pattern grains and the intensity of the applied disturbance. The numerical simulation shows how the building characteristic of the length of sensing zone, combined with image processing, can be manipulated to control the metrological performance of the sensors.
An effective approach for general measurement based on weak value amplification using non-Gaussian broadband light sources is demonstrated. This scheme can reduce the difficulty of preparing the measurement apparatus and correcting the systematic error caused by the imperfection of device's wave function, thus making the weak-value amplification scheme more convenient and robust for practical field applications. The influence of several common noise sources in a general application based on weak value amplification is analyzed theoretically and examined experimentally. A purely imaginary weak-value phase measurement system is considered for the noise model verification experimentally. In this we show how to optimize the precision of measurement in a unique solution that takes into account the interplay between precision and uncertainty, and explicate the ramifications of such a compromising and pragmatic approach.
Svitlana M. Levchenko, Artem Pliss, Xiao Peng
et al.
Abstract Optical imaging is a most useful and widespread technique for the investigation of the structure and function of the cellular genomes. However, an analysis of immensely convoluted and irregularly compacted DNA polymer is highly challenging even by modern super-resolution microscopy approaches. Here we propose fluorescence lifetime imaging (FLIM) for the advancement of studies of genomic structure including DNA compaction, replication as well as monitoring of gene expression. The proposed FLIM assay employs two independent mechanisms for DNA compaction sensing. One mechanism relies on the inverse quadratic relation between the fluorescence lifetimes of fluorescence probes incorporated into DNA and their local refractive index, variable due to DNA compaction density. Another mechanism is based on the Förster resonance energy transfer (FRET) process between the donor and the acceptor fluorophores, both incorporated into DNA. Both these proposed mechanisms were validated in cultured cells. The obtained data unravel a significant difference in compaction of the gene-rich and gene-poor pools of genomic DNA. We show that the gene-rich DNA is loosely compacted compared to the dense DNA domains devoid of active genes.
We have shown that when sharply focusing a linearly polarized optical vortex with topological charge 2, in the near-axis region of the focal plane, not only does a reverse energy flow (the negative on-axis projection of the Poynting vector) occur, but also the right-handed circular polariza-tion of light. Moreover, due to spin-orbital angular momentum conversion, the on-axis polarization vector and the transverse energy flow rotate around the optical axis in the same direction (counter-clockwise). If an absorbing spherical microparticle is put in the focus on the optical axis, it will rotate around the axis and around its center of mass counterclockwise. Numerical simulation results confirms the theoretical predictions.