A single GaAs/GaAsSb/GaAs quantum well having a valence band profile was described in this study using the V-shaped potential. An external static electric field (E-field) and a high-frequency intense laser irradiation were utilized to examine the first-order linear and third-order nonlinear optical properties. The theoretical modeling was achieved using a compact-density matrix and iterative process in a two-level system framework. The position-dependent effective mass approximation was applied to solve the Schrödinger equation and evaluating the energy states and their corresponding wavefunctions for the two lowest bound states within the quantum well’s valence band with regards to a heavy hole. We extended the investigation of the single V-shaped potential by incorporating the effects of the E-field, the well’s half-width, and antimony (Sb) content on optical characteristics. The study on the combined effects of the intense laser field and the mentioned factors revealed that the peak positions and amplitudes of the linear and nonlinear optical characteristics were strongly influenced by variation in the laser strength. Specifically, we observed, that under higher laser dressing parameters, the application of the electric field played an important role. This occurred when the impact of the well’s half-width and Sb content became prominent at values of lower laser-dressing parameters. It is significant to note that our findings will have potential real-world applications in photonics, optoelectronics, and related areas.

The band-gap of InxGa1−xN can cover a wide range of electromagnetic radiation of the solar spectrum and offers a method for using it in photovoltaic solar cells. A solar cell structure consisting of InxGa1−xN/GaN superlattice (SL) piled up between p-GaN and n-GaN is modeled and simulated. The impact of variations in the indium mole fraction and step graded SL having different quantum well thicknesses are analyzed. The results indicate that high indium content leads to lattice mismatch, decrement of fill factor, and development of strain in the quantum wells that reduce the overall efficiency. To increase the efficiency of the solar cell, a step graded 20 SL with a 5 nm quantum well thickness is introduced, and the highest efficiency of 22.6% is obtained. The use of a step graded SL InGaN cell allows for constructing real structures with the possibility of obtaining the enhanced power conversion efficiency compared with a conventional quantum well solar cell using SILVACO TCAD.

Due to the limited study, this work engineers the parameters controlling the rate of absorbed energy from a double quantum dot (DQD)-metal nanoparticle (MNP) system at plasmonic electromagnetically induced transparency (PEIT) considering the strong coupling between DQD and MNP. The modeling is of the material property for which the energy states and transition momenta are calculated. The analysis considers the orthogonalized plane wave between the wetting layer (WL)-QD transitions. A huge (10−5 W) total absorption rate (Qtotal) from the system is attained. This result is higher by four orders and the power applied is less by three orders than that obtained in the literature. Many features are studied. Neglecting the WL, the system spectrum is similar to the left-handed picture of the system with WL. The value of Q depends on the situation of the QD energy states through the variation of the QD size, MNP radius, and distance separating the system. In the DQD-MNP hybrid system, the controlling factor that gives a high Qtotal in the PEIT case is the DQD combination with a weak probe and enough pump, i.e., the DQD structure works as a whole structure, not as two QDs working separately. Such a structure allows for manipulating the flexibility of carriers between DQD states that are not found in other structures. From the results, one can conclude that DQD behavior under the pump, probe, and single tunneling component produces two transparent windows. Adding a second tunneling component creates four transparency windows depending on the values of these applied parameters.

We introduced a tunable terahertz broadband absorber with near-unity absorption based on a graphene metamaterial. A periodic array of star-shaped ring graphene resonators along with a silicon dioxide substrate backed with a ground plane forms the absorbing structure. The absorption rate of the ultimate optimal absorber is more than 90% in the 0.8 to 2.4 terahertz frequency range, which is equivalent to a relative bandwidth of 100% at a central frequency of 1.6 terahertz. It is shown that the proposed structure retains its absorption bandwidth with an absorption level of more than 75% up to a 60-deg elevation angle for different wave polarizations. In addition, by increasing the chemical potential of graphene in the proposed structure from 0.1 to 0.9 eV, the absorption rate of the structure can be tuned from 40% to nearly 100%. The effects of different geometrical parameters of the structure on the absorption rate of the structure are also investigated, and the absorption mechanism of the presented absorber is investigated by interference and impedance matching theories. Finally, the simulation results are compared with calculated analytical ones, where good agreement between the results is observed. The proposed absorber has potential application in terahertz frequencies such as cloaking, modulators, tunable filters, sensors, and imaging systems.

A nested ring resonator structure has been devised on a silicon-on-insulator platform, incorporating a feedback path through the addition of a port to the device. This design selectively enhances resonant wavelengths while effectively suppressing numerous consecutive resonant wavelengths by ∼30 dB. Consequently, it significantly expands the free spectral range (FSR) by over 85 nm, exceeding 20 times the FSR achieved without the feedback path. The resonant peak wavelength can be tuned by ∼40 nm/μm change in the feedback path, offering a broader range for refractive index sensing. The impact of the additional phase control parameter length in the feedback path was investigated. Theoretical analysis was followed by finite differential time domain simulations to validate the results. Various device parameters were systematically adjusted to observe a substantial increase in the FSR and improved controllability over peak transmission.

A compacted random laser with a triple optical cavity is designed by directly coupling the compound between three cavities: the fundamental, ring, and external cavities. The laser action in this counterintuitive cavity is enabled by feedback from strong reflections on the inner and external surfaces, as well as scattering centers silver nanowires. This unique property of the triple optical cavity results in a lower laser threshold and enhanced emission spectra. These results provide up new possibilities for designing devices integrated and miniature technology.

We demonstrate the fabrication of an optical nanofiber tip (ONFT) using a two-step chemical etching technique. This technique employs 30% and 24% hydrofluoric (HF) acid for the first and second steps, respectively. In the first step, a silica single-mode fiber with a clad diameter of 125 μm and a core diameter of 9 μm is immersed in the HF acid for 90 min. The resultant fiber diameter is reduced to ∼45 μm. In the second step, the fiber is again immersed in the HF acid for 60–80 min. The etching time is controlled to achieve the desired tip diameter of the ONFT. We characterize fabricated ONFTs by measuring the optical transmission and surface morphology. The observed optical transmissions are more than 30%, and the tip diameters are less than 500 nm. The measured results readily reveal the merit of the employed technique as it is easy and cost effective. Due to the strong confinement of the electromagnetic field at the tip of ONFTs, these structures have versatile platforms with potential applications in sensing, photonics, and quantum optics.

This work proposes a mask design method to change the film thickness distribution for the rotary plane coating machine, and successfully deposits a continuously variable filter. The results indicate that the test spectrum exhibits linear gradient passband filtering characteristics at different positions along the spatial direction. The continuously variable filter operates between 650 and 1050 nm, with the linear dispersion coefficient of 32.92 nm/mm over 12 mm. The peak transmittance of the filter is more than 80%, the transmittance of cutoff band is less than 0.1%, and the half bandwidth of the passband is almost consistent with 1.5% of the central wavelength. These parameter indicators fully meet the design requirements.