We present a groundbreaking and versatile approach to multi-mode rainbow trapping in photonic crystal waveguides (PCWs), overcoming long-standing limitations in photonic device design. Our innovative semi-bilayer PC design, formed by stacking two PCs, enables the realization of new photonic modes that were previously inaccessible, leading to enhanced device flexibility, improved performance, and increased resilience to defects and imperfections. By meticulously engineering a chirped PC within the PCW, we achieve multi-mode light trapping at distinct positions for different frequencies along the waveguide, effectively creating a rainbow of light. This study paves the way for efficient and robust trapping and demultiplexing of multiple wavelengths, opening up new avenues for on-chip nanophotonic applications. Moreover, the realization of ultra-high-quality (Q) factor Fano resonances within the waveguide cavity unveils unprecedented possibilities for designing on-chip nanophotonic devices. The diverse array of Fano resonances holds immense potentials for developing novel optical filters, switches, and lasers with exceptionally low thresholds. Our proposed structure offers a more compact, efficient, and robust solution for multi-wavelength photonic device applications.

Chemical structural engineering is a helpful method to design the semi-conductors for organic solar cells (OSCs).
The understanding of structural and electronic properties of materials is essential for designing and calibration of
materials. By making structural adjustments at the terminal position, new small molecule acceptors can be
created. Electronic properties are studied in detail. Electrostatic potential both in qualitative and quantitative
way is studied to explore the electron density distribution. The electron density is signifcantly changed on the
change of terminal groups. The excited state behaviour has also undergone a noticeable alteration. The increase
in electron-defcient character at the terminal location causes the absorption spectra to shift to the red. The
structural changes have an important effect on non-covalent interactions also. Through molecular dynamics
(MD) simulations, the bulk behaviour of pure small molecule acceptors and their blend with polymer donor PM6
is examined. Radial distribution function is attained from MD simulations. The alteration in terminal groups has
signifcantly changed the packing behavior of pristine acceptors and their blend with polymer donor.
 

Topological photonics and topological photonic states have opened up a new frontier
for optical manipulation and robust light trapping. The topological rainbow can separate different
frequencies of topological states into different positions. This work combines a topological
photonic crystal waveguide (topological PCW) with the optical cavity. The dipole and quadrupole
topological rainbows are realized through increasing cavity size along the coupling interface. The
flatted band can be obtained by increasing cavity length due to interaction strength between the
optical feld and defected region material which is extensively promoted. The light propagation
through the coupling interface is built on the evanescent overlapping mode tails of the localized
felds between bordering cavities. Thus, the ultra-low group velocity is realized at a cavity
length more than the lattice constant, which is appropriate for realizing an accurate and precise
topological rainbow. Hence, this is a novel release for strong localization with robust transmission
and owns the possibility to realize high-performance optical storage devices.
 

Valley photonic crystals (PCs) play a crucial role in controlling light flow and
realizing robust nanophotonic devices. In this study, rotated gradient valley PCs
are proposed to realize topological rainbow trapping. A topological rainbow is
observed despite the presence of pillars of different shapes, which indicates the
remarkable universality of the design. Then, the loss is introduced to explore the
topological rainbow trapping of the non-Hermitian valley PC. For the step-angle
structure, the same or different losses can be applied, which does not affect the
formed topological rainbow trapping. For a single-angle structure, the applied
progressive loss can also achieve rainbow trapping. The rainbow is robust and
topologically protected in both Hermitian and non-Hermitian cases, which is
confirmed by the introduction of perturbations and defects. The proposed
method in the current study presents an intriguing step for light control and
potential applications in optical buffering and frequency routing.
 

Due to the large versatility in organic semiconductors, selecting a suitable (organic semiconductor) material for photodetectors is a challenging task. Integrating computer science and
artificial intelligence with conventional methods in optimization and material synthesis can guide
experimental researchers to develop, design, predict and discover high-performance materials for
photodetectors. To find high-performance organic semiconductor materials for photodetectors, it is
crucial to establish a relationship between photovoltaic properties and chemical structures before
performing synthetic procedures in laboratories. Moreover, the fast prediction of energy levels is
desirable for designing better organic semiconductor photodetectors. Herein, we first collected large
sets of data containing photovoltaic properties of organic semiconductor photodetectors reported in
the literature. In addition, molecular descriptors that make it easy and fast to predict the required
properties were used to train machine learning models. Power conversion efficiency and energy
levels were also predicted. Multiple models were trained using experimental data. The light gradient
boosting machine (LGBM) regression model and Hist gradient booting regression model are the
best models. The best models were further tuned to achieve better prediction ability. The reliability
of our designed approach was further verified by mining the photovoltaic database to search for
new building units. The results revealed that good consistency is obtained between experimental
outcomes and model predictions, indicating that machine learning is a powerful approach to predict
the properties of photodetectors, which can facilitate their rapid development in various fields.
 

The sensitivity of graphene surface to adjacent conditions plays an important role that modifies the performance and characteristics of graphene devices working under ambient conditions. Quartz is a dielectric transparent material with excellent optical transmission and therefore graphene/quartz is widely used in graphene device technology. Here, graphene/quartz and graphene/plasmonic nanoparticle/quartz structures were investigated using Raman spectroscopy for applications in nanotechnology like graphene quartz fiber (GQF) multifunctional electrode. Optically induced shift of the Fermi level of graphene monolayer on quartz substrates and on Ag nanoparticles (NPs) distributed on quartz substrates was tracked by increasing the applied laser power. Strained graphene attached to quartz substrate, thermal effects, and charge transfer were discussed using the evolution of the G-peak characteristics. Well …

Tunning the carrier concentration n and the position of Fermi-level E F in graphene monolayers has a great impact on the design and fabrication of next generation graphene-based devices. Raman spectral properties of graphene/SiO 2/Si and graphene/Al 2 O 3 are investigated over a wide range of laser power (P L= 1 to 25 m W). The increase in P L results in significant variations in position and half-width of the G-band, allowing the determination of n and E F using nonadiabatic fitting. The initially formed p-type graphene is converted to n-type with increasing P L due to charge transfer to/from graphene with the substrate interfacial defect states and/or redox interactions with environmental gas. Whereas n and E F of the graphene/SiO 2/Si reach saturation at P L= 12 m W, those of graphene/Al 2 O 3 exhibit a monotonic increase before saturating at P L> 21 m W. A noticeable enhancement in graphene quality …

In this work, we employed the casting procedure to synthesize polymer hybrids from epoxy with acrylic polymer coating with nanoclay. The investigated polymer hybrid was composed of 80% epoxy resin, 17% acrylic polymer solution, and 3% nanoclay. The polymer hybrid samples were ranged in thickness from 1 to 3 mm. The influence of the sample’s thickness on thermal stability, thermal conductivity, and mechanical properties, as well as the constant angle of polymer hybrids were examined. The structural investigation revealed that the loaded nanocaly is crystalline with an average crystal size of 56 nm inside the amorphous polymer matrix. Also, it consistently dispersed throughout the epoxy matrix, showing that the tiny nanoparticles were meant to agglomerate with one another. The maximum thermal stability was found in polymer hybrids with a thickness of 2 mm, and the contact angle was closed to 90° for polymer hybrids with a thickness of 1.5 mm. The hardness values were remained constant around 73 ± 1 and were unaffected by sample’s thickness. Meanwhile, increasing the polymer hybrid's thickness slightly improves the impact and flexural strength values. The anticipated value of the wear rate was slightly changed while increasing with applied force. As the thickness of the synthesized polymer hybrids was rose from 1 to 3 mm, the thermal conductivity was fell from 0.47 to 0.32 W/m K. The synthesized hybrid epoxy and acrylic polymer coating/nanoclay was exhibit significant thermal and mechanical stability, as well as hydrophobicity, and hence may be employed for floor painting and waterproofing applications.

The effect of Ag content on the linear and nonlinear optical characteristics of thermal evaporated  Se90−xTe10Agx thin films, 100 nm thick, (where x = 0, 2, 4, 6, and 8 at.%) has been examined. The optical measurements were reviewed in the wave length range of 390–2500 nm based on the transmittance and reflectance data, and the amorphous state of the as-prepared thin film was confirmed by X-ray diffraction. The absorption coefficient, extinction coefficient, bandgap, optical density, optical conductivity, dissipation factor, and other optical properties were examined and discussed. For all of the samples, the extinction coefficient of Se90−xTe10Agx declines as the wavelength and Ag concentration rise, whereas the absorption coef f icient increases linearly with incident photon energy. Furthermore, the optical bandgap and the width of localized states alter in the exact opposite direction, which is consistent with previously reported findings. The decrease in the optical band gap as Ag concentration increases could be attributable to an increase in the amount of disorder in the materials and the density of defect states. Other critical optoelectronic characteristics are also determined, and they are found to be influenced by the Ag ratio and photon wavelength. These materials may be ideal for optical memory applications due to their high absorption coefficient and compositional dependence of absorption.