A perforated micro-ring resonator (PMRR) on the flexible SU-8 substrate is proposed and theoretically demonstrated for detecting the refractive index (RI) and the pressure simultaneously. Once a perforation defect is introduced, the symmetric and the asymmetric standing wave modes (SWMs) are formed during the mode splitting. The energy distributions of the two SWMs are quite different so that the sensitivities of two modes toward the variation of RI and pressure applied to the device show differences. Through the numerical simulations, we obtain an RI sensitivity of 76.03  nm  /  RIU and a high pressure sensitivity of 5.37  pm  /  kPa for the symmetric SWM, and an RI sensitivity of 68.82  nm  /  RIU and a high pressure sensitivity of 6.15  pm  /  kPa for the asymmetric SWM. By solving a second-order sensitivity inverse matrix, we can measure the changes in RI and pressure simultaneously, thereby eliminating the influence of the strain-optical coupling effect in the field of flexible biosensor. Therefore, the proposed structure provides an approach to achieve flexible biosensing application in the real world and has tremendous potentiality in achieving multi-sensing applications.

The low light extraction efficiency (LEE) stemming from the transverse-magnetic dominant emission is one of the major factors limiting the performance of aluminum gallium nitride (AlGaN)-based deep ultraviolet (UV) light-emitting diodes (LEDs) when the light emission wavelengths are close to 200 nm. These wavelengths, nonetheless, are pivotal to applications including sensing and sterilization and are considered human safe. We investigate the LEE of AlGaN/AlN nanowire (NW) deep UV LEDs emitting at 225 nm, with a focus on the top-surface LEE by considering different NW arrangements, typical NW spacings and radii from AlGaN NWs grown by selective area epitaxy, the influence of Si on the LEE in comparison to an Al reflector, and graphene as the top electrode. Our results show that given the selected range of design parameters, the top-surface LEE for honeycomb, square, and hexagonal lattices can be up to around 42% for complete devices on Si with the graphene top electrode; and compared to using an Al reflector, the Si substrate does not reduce LEE considerably. In the end, the light extraction mechanism is discussed by simulating the two-dimensional photonic crystal band structures.

The improvement of a green synthetic approach that focuses on the use of olive leaf extract took place to produce silver nanoparticles (AgNPs). This synthesis is known for its cost efficiency and ecological safety, with the potential to be applied in massive AgNP production. The cytotoxic, anticancer, and antioxidant activities of olive leaf extracts with AgNPs were examined on breast cancer cell lines following preparation of olive leaf extracts utilizing a method of extraction at a temperature of (0°C/8 h). Total flavonoids and phenolics for olive leaves with extraction through ethanolic and water solvents were 43.52  mg  /  ml and 132.9 and 64.73  mg  /  ml and 293.32, respectively. UV-Vis spectroscopy that has the sizes of absorption peaks from 420 to 440 mm was used to describe the synthesized AgNPs nanoparticles. Scanning electron microscopy verified these particles, specifying that they are characterized by the spherical shape of and being 100 nm on average. AgNPs’s antioxidant activity was significant. Additionally, a cytotoxic activity dependent on concentration was shown by green synthesized AgNPs. This is the initial study that established olive leaf extracts biological activity at 0°C/8 h temperature utilizing ethanol and water solvents followed by biosynthesized AgNPs from the extracts and their therapeutic potential.

We propose an all-dielectric metasurface with strong polarization sensitivity and large-modulation-depth for potential multiple switching applications. We show that the proposed metasurface can be efficiently tailored through symmetry breaking to support strong toroidal and trapped dipole responses across the near infrared spectrum with high Q-factors. Such two responses can be dynamically switched on and off simultaneously only through changing polarization of incident light, and the direction of toroidal dipole can be rotated 90 deg in two separate frequency regimes. The maximum values of the amplitude modulation depth around responses can almost reach 100% simultaneously, respectively, providing the potential applications in sensing, lasing, switching, and spectral filtering.

A numerical model allows analysis of optical gain according to the electronic properties of AGaN/GaN multiple quantum well laser diode (MQWLD) under hydrostatic pressure. Finite difference techniques are used to acquire energy eigenvalues and their corresponding eigenfunctions of AGaN/GaN MQWLD. The hole eigenstates are calculated via a 6  ×  6  k  .  p method under applied hydrostatic pressure. It was found that the depth of the quantum wells, bandgaps, band offset, electron, and hole density increased with the increase of hydrostatic pressure. The electron and hole wave functions will have less overlap, the amplitude of the optical gain increases, and heavy hole and light hole interband relaxation time, and their excitons binding energy decreases with increasing pressure. A change in pressure of up to 10 GPa caused the optical gain peaks of light and heavy holes to shift to a high photon energy of up to 120 meV and enhanced the optical gain up to 1.7  ×  10⁵  m^−  1.

We present a copper indium gallium selenide (CIGS) solar cell with improved performance, numerically simulated using LUMERICAL FDTD and DEVICE Multiphysics simulation software and considering the charge transportation, ambient temperature, buffer layer thickness, and defect density for detailed analysis. One of the significant concerns of the existing CIGS solar cells is the presence of the toxic cadmium sulfide (CdS) buffer layer and higher buffer/absorber layer interface dominant recombination. Replacing CdS with zinc sulfide (ZnS) is a propitious way to address such issues and enhance the CIGS solar cell’s performance while achieving efficiencies similar to that of the CIGS solar cell with CdS as the buffer layer. Furthermore, the performance is improved by employing a transparent conductive oxide of fluorine-doped tin oxide (FTO) and zinc tin oxide (ZTO) window layer for better charge flow and low-current losses. However, the real solar cell operating conditions are entirely different from the predefined standard conditions. To get a more detailed analysis, we demonstrate the impact of variations of operating temperature, ZnS buffer layer thickness, defect density on the short-circuit current, open-circuit voltage, and overall performance of the solar cell. We found that the simulated efficiency of the proposed CIGS solar cell (FTO–ZTO/ZnS/CIGS/Mo) with ZnS and FTO–ZTO layer is 29.6% with a short-circuit current of 49.3  mA  /  cm², higher than that of the CIGS solar cell (Al:ZnO/CdS/CIGS/Mo) with CdS that was achieved in our previous work. Thus the study can help to develop a more promising, efficient, and cost-effective CIGS solar cell.

Vanadium nitride (VN)-based metamaterial absorber was investigated for ultra-wideband (UWB) nearly perfect absorber in the visible to infrared regime of the electromagnetic spectrum considering four different VN samples, namely VN₆, VN₈, VN₁₀, and VN₁₂. The absorption properties were extracted for the transverse electric and transverse magnetic incidence waves under different obliquities, and also, considering different parametric conditions of the metamaterial. The constitutive properties of VN samples were initially extracted, followed by the effective constitutive properties of metasurface comprising the nanostrips of VN₆ and VN₁₀ mediums as the illustrative examples. The results determine achieving nearly perfect UWB absorption in the stated regime of operating wavelength. Spectral characteristics were also obtained while using other reflectors at the bottom. The results demonstrate using VN at the bottom yields significantly improved spectral features. The absorption related results were also evaluated exploiting the interference theory, and the obtained discrepancies were highlighted.

Exciton–LO phonon interaction of the Fröhlich type is studied in the CdS/CdSe/CdS asymmetric double quantum well under an applied laser field. The intensity of laser effect on the exciton binding energy, oscillator strength, optical transition energies, and third-order harmonic generation are investigated by changing the right well sizes and barrier sizes. The laser-associated confined energies and their corresponding binding energies are brought out with the variation of well sizes. The position-dependent potential is altered by the laser-associated parameter. The laser-field-dependent third-order optical susceptibilities due to interband transitions in the asymmetric well are investigated. The effective Coulomb potential, using the Aldrich and Bajaj polaronic effect, is included in the Hamiltonian. The results show that the laser field considerably affects the confining potential of the quantum well and causes a drastic deformation of the confining potential profile. The obtained optical nonlinearities suffer a redshift in the asymmetric quantum well; also, their peak values are determined by the dipole matrix elements.

An approach has been suggested for the simulation of a quantum dot reflective semiconductor optical amplifier (RSOA) with wideband optical gain. This model is implemented by superimposing different quantum dot groups with various radii using solution process nanotechnology, which is both practical and frugal. Also, few works have been done, superimposing QD groups in RSOAs. A numerical method has been used for solving coupled rate equations. This method is a perfect approximation for understanding this device; because analytical solutions are not possible to further investigate the model. Using this method, a wideband optical gain of about 30 dB, covering broadband from 460 to 730 nm, has been obtained by using CdS_xTe_{1  -  x} with different mole fractions. Furthermore, this optical gain is not even limited to this value if more groups get exploited. The proposed model results in about 270 nm optical bandwidth, making this device suitable for implementing wavelength division multiplexing in optical networks by designating different channels to various signals. In addition, it shows a high signal-to-noise ratio (about 1000), making it a great candidate for use in optical communications. Using this technique, one step is taken to the development of high-speed broadband WDM passive optical networks. Also, different bands in the lightwave spectrum can be used and only one needs to choose suitable materials for synthesizing QDs to operate in the desired wavelengths.

Plasmonic nanoparticles are promising ways for the efficiency enhancement of thin-film solar cells. We have taken into account the bare silicon wafer and the embedded thin-film silicon solar cells with Au nanodiscs array. We study these geometries of thin-film silicon solar cells and find the effect of Au nanoparticles on light transmission and reflection spectrum, power absorption, generation rate, power electric, and short-circuit current density; and for this, we have used finite difference time domain, FDTD software. We also consider the near-field electric intensity in the vicinity of nanoparticles with different sizes, which are known as a solar cells efficiency enhancement mechanism. Our study can be useful for new perspectives for antireflection coating applications and light management in silicon solar cells.

We propose a compound structure constructed by two magnetic cavities with parity-time (PT) symmetric configuration. Through the calculations based on transfer matrix, we find that the structure system has some unique properties that the usual PT symmetric structures do not have. The four incident conditions of the structure produce two sets of transmittance spectra and four different reflectance spectra in which the unusual amplification and absorption are shown. The huge amplification and absorption can be precisely tuned through the magnetic field. Furthermore, the amplification and absorption around the pole can be reversed through the change of incidence directions. Although the analysis of the scattering matrix shows that the transmission and reflection are not nonreciprocal, the diverse modulation ways (magnetic field and incidence directions) will make the structure more useful in the design of photonic switching and optical modulator.

One way to sense the presence of analytes in a solution is by exploiting surface plasmon resonance (SPR) at a metal/dielectric interface in the Turbadar–Kretchsmann–Raether (TKR) configuration. One of the ultimate goals of sensing is to be able to detect multiple analytes in a single solution simultaneously. Numerical studies show that two-analyte sensing can be achieved by having an artificial neural network (ANN) analyze reflectance data when either a columnar thin film (CTF) or a chiral sculptured thin film (CSTF) is used as the partnering dielectric material in the TKR configuration. Both CSTFs and CTFs are porous with the former being periodically non-homogeneous in the thickness direction. In addition, vertical multiplexing is to be incorporated in these sensors, as the two analytes were assumed in the theoretical model to be differentially concentrated around two different metal layers within each sensor. With respect to classifying nine different solutions, the CTF-based sensor with vertical multiplexing delivered a theoretical average accuracy of 92.3% while the analogous CSTF-based sensor delivered an average accuracy of 94.5%, with adequate training of the ANN. The non-SPR features in the reflectance data play a significant role in enhancing the accuracy of classification.

We report the performance of silicon-on-insulator medium-length extended microcavity (3 to 4.5  μm long) one-dimensional photonic crystal waveguide. Quality-factor (Q-factor) values ranging from 2000 to 37,000 were observed. The waveguides/wire were fabricated using an inductively coupled plasma reactive ion etching with SF₆ and C₄F₈ gasses. Optical transmission of the design is heavily influenced by the surface roughness of the waveguide wall. We achieved a good free spectral range control for resonance frequency separations in between 39 and 65 nm. Supported and suspended microcavity structures for the case of a medium-length extended microcavity were compared. We observed an inferior performance in terms of the optical transmission and Q-factor in the latter. We have selected 4-μm microcavity length for comparison. The suspended structure was obtained by utilizing the wet etching technique on the same device. A high Q-factor value of ∼26,000 was observed in one of the resonances excited for cladding-layer supported extended microcavity. However, the Q-factor was reduced to ∼17,000 after removing the silica cladding beneath the silicon waveguide core.