International Journal of

---

Thin films of indium doped zinc sulfide (ZnS) for different indium (In) concentrations (x=0.0 - 0.8) were deposited onto glass substrate by spray pyrolysis method at 523K temperature. Aqueous solution of zinc acetate, indium chloride and thiorea were used to deposit the In-Zn-S film. The deposited thin films were characterized by Energy dispersive X-ray (EDX), Scanning electron microscopy (SEM), X-ray diffraction (XRD), and by UVvisible spectroscopy. The XRD spectra of In-Zn- S revealed both the amorphous and polycrystalline property for different In concentration. The EDX showed a well stoichiometric result of different compositions of In in ZnS thin films. The granularity of irregular shape is observed in In doped ZnS thin films surface by scanning electron microscope. From the absorbance and transmittance data it is observed that the band gap energy is decreased from 3.75eV to 3.1eV with the increase of In concentration in ZnS.

---

For a fiber optical surface plasmon resonance (SPR) sensor a short part of its cladding should be removed to coat a thin layer of a metal. Usually this is problematic when an optical fiber with small core diameter is used. In this paper, a new method using µliter droplet of the HF acid for short fiber optical taper fabrication is reported. Using this method in a multi-mode optical fiber with the core/cladding size of 50/125 µm a 2 mm long taper with 40 µm diameter is fabricated. Roughness of its surface is investigated using an atomic force microscopy. The measured mean value of the roughness is about 8 nm. A 60 nm thin layer of pure silver is coated on the taper surface in order to investigate its performance using a fiber optical SPR sensor.  Using this SPR fiber sensor measurement of the lead concentrations in water ranging from 0.1 to 10 part per million (ppm) is reported.

---

ta charset="UTF-8" >We investigate the Cu₂FeSnS₄ (CFTS) thin film. The raw materials of this thin film are copper, iron and tin, which are mixed in the form of tablets and then are deposited on a glass substrate through the process of pulsed laser deposition (PLD). The produced metallic thin films are then sulfurized to carry out the process of merging the element sulfur in the thin films and forming CFTS structure. We investigate the influence of sulfurization temperature and the laser pulse energy in the PLD process on the deposited CFTS thin films. The X-ray diffraction (XRD), Raman and UV-Vis analyses’ results show that by decrease in sulfurization temperature from 600 °C to 550 °C the crystal quality of the thin films is improved, which is realized by increase in volume and quality of the CFTS phase. On the other hand, the results confirm that the laser fluence is a decisive factor which should be taken into account to achieve an optimized structure.

---

This article examines the impact of graded-index reflectors (GIRs) constructed from cholesteric liquid crystals (CLCs) on the modification of escape-cone loss and the improvement of luminescent solar concentrator (LSC) efficiency. GIRs are comprised of a structure in which the refractive index changes gradually with a spatial function. In this study, the LSC is a planar optical waveguide made of Poly (methyl methacrylate) (PMMA) with dimensions of 5×5×0.5 cm³ and contains CH₃NH₃PbBr₃ perovskite material as a fluorophore. Two types of GIRs are employed at the bottom of the LSC: periodic and quasi-periodic GIRs. Periodic reflectors (PRs) have a refractive index matrix that gradually changes with a periodic sinusoidal function, while the refractive index matrix of the quasi-periodic reflectors (QPRs) gradually changes with a chirped sinusoidal function. To analyze the models of the study, Monte-Carlo and Finite-Difference Time-Domain (FDTD) methods were utilized in conjunction with experimental results. The results indicated that the reflection band of a PR exhibited the maximum overlap (lowest escape cone) with the dye emission spectrum when the mirror's reflection band underwent a redshift of 20 nm compared to the dye emission spectrum. On the other hand, the QPR generated a broader reflection band, resulting in complete overlap and higher efficiency. Moreover, GIRs enhanced sunlight absorption in the LSC by reflecting transmitted solar photons through it. The optical efficiency (OE) of the LSC increased by 12% (33%) once a periodic (quasi-periodic) reflector is utilized. Furthermore, GIRs reduced escape cone loss, thereby increasing reabsorption, and subsequently, the system selected a lower optimal concentration to minimize reabsorption losses.