Iraqi Journal of Laser

This study investigates the structural and optical properties of Fe-doped (CuO: ZnO) thin films with varying Fe contents (x = 0.1–0.5%) deposited on glass substrates via pulsed laser deposition (PLD) at ambient temperature under a vacuum of 1 × 10⁻² mbar. X-ray diffraction (XRD) confirmed that all films maintained a monoclinic polycrystalline structure, with grain size decreasing with increasing Fe concentration. Energy Dispersive X-ray Spectroscopy (EDS) verified the successful incorporation of Fe without altering the Cu and Zn composition. Increasing Fe concentration significantly affected the optical transmission, absorption, refractive index (n), extinction coefficient (k), and dielectric constants, demonstrating that Fe doping strongly modifies the structural, optical, and dielectric properties of CuO: ZnO thin films.

Laser scribing of the front-layer metal contact in thin-film silicon solar cell is one method that
enhances optical absorption through localized surface plasmon resonance (LSPR) induced at the laser-scribed
gold nano-grooves. A new approach investigates both the plasmonic effect and increasing the absorption of the
gold via laser scribing to improve the cell performance. A 3D ultra- thin film silicon solar cell (dimensions of
400 × 400 × 900 nm3 for width, length, and height) was designed, with a 50 nm thick gold front contact scribed
at groove depths of 10, 20, 30, and 40 nm (fixed width of 100 nm). COMSOL Multiphysics software version
6.2, using the finite element method (FEM), was employed to design and numerically investigate the proposed
cell. The results revealed a maximum photocurrent of 24.66 mA/cm2 at a scribed depth of 40 nm. The laserscribed
nano-grooves excite localized surface plasmon resonances at the gold-silicon interface, enhancing
electromagnetic field confinement and light trapping in the ultra-thin silicon layer. It is concluded that the laser
scribing of the front gold contact improves the light absorption, leading to a significant increase in photogeneration
rate and photocurrent density due to plasmonic field enhancement.

In this study, Ti6Al4V alloy was exposed to a Q-switched Nd:YAG laser (wavelength 1064 nm, 6 Hz
repetition rate, 10 ns pulse duration, and 4 mm spot size) with energies of (280-460) mJ. This process is referred to as
laser surface modification (LSM). The effect of laser energy on crystalline structure, surface wettability, hardness,
and topography was systematically evaluated using appropriate measurement techniques such as (XRD, contact angle,Vickers micro hardness tester, SEM). Significant increases were observed in hardness and wettability during thedecrease in the contact angle and along with an enhancement in other surface properties.

Laser direct energy deposition (LDED) was employed to fabricate low-carbon stainless steel 316L and
to evaluate the influence of processing parameters on porosity, relative density, and microhardness. A fiber laser
system operating at 1070 nm (YLS-3000-CUT, IPG ABB) was used. The spot size was 1.2 mm, the powder feed
rate was 9.5 g/min, the layer thickness was 0.2 mm, the carrier gas flow rate was 7.5 L/min, and the shielding gas
flow rate was 25 L/min. Laser power (420, 600, and 800 W) and scan speed (20, 25, and 30 mm/s) were
systematically varied, producing nine samples with linear energy densities between 14 and 40 J/mm and volumetric
energy densities from 59 to 167 J/mm³. Microstructural features and pore morphology were examined using optical
microscopy and scanning electron microscopy. Porosity and relative density were quantified by full cross-sectional
image analysis. Microhardness was measured using a Vickers indenter with a 300 g load and 10 s dwell time.
Microhardness values ranged from 185.4 to 207.3 HV. Porosity values varied between 0.198% and 0.831%, while
relative density ranged from 99.169% to 99.802%. Lower volumetric energy densities produced reduced porosity
and increased relative density at all scan speeds. The minimum porosity (0.198%) and maximum relative density
(99.802%) were obtained at a scan speed of 30 mm/s and a volumetric energy density of 59 J/mm³. The results
quantify the effect of laser power and scan speed on densification and mechanical response in LDED-processed
316L and define a limited processing window for defect minimization.

Cadmium sulfide (CdS) thin films have been fabricated on glass substrates via the spin-coating method, followed by thermal annealing at 100°C, 150°C, and 200°C. Optical studies indicated that the deposited films possess high transparency in the visible and near-infrared regions, with transmittance values reaching approximately 75%. The films exhibited a direct optical band gap, which showed a gradual decrease from 2.2 eV to 1.6 eV as the annealing temperature increased. Additionally, increasing the annealing temperature resulted in noticeable improvements in film homogeneity and crystallinity. These findings underscore the crucial role of thermal annealing in modulating the optical properties of CdS thin films, thereby improving their suitability for optoelectronic applications.

Copper phthalocyanine (CuPc) films exhibit strong absorption as well as chemical stability against visible light and hence are attractive organic semiconductors for an optoelectronic device. In the present work, we have studied the influence of 650 nm laser irradiation on the 478.4 nm Cupc thin film and recorded its photodetector behavior. X-ray diffraction analysis showed increased crystallinity of laser-treated samples, in which the crystallite size enhanced from 30.48 to 39.03 nm with diminished microstrains. The average grain size increased from 35.77 nm to 95.19 nm, while the surface roughness decreased as observed by an atomic force microscope (AFM), evidencing a remarkable grain growth and surface smoothing process. The optical properties revealed small changes in the π–π* transitions and a slight increase in the optical band gap from 1.82 to 1.84 eV, indicating a decrease in the disorder of the structure. Hall effect measurements revealed that an increase in the carrier mobility from 0.16 to 28.9 cm²/V•s resulted in good electrical properties despite a decrease of the free electron concentration (n) due to the hole compensation mechanism. Meanwhile, the responsivity of laser-treated CuPc photodetector dramatically improved from 54.92 to 190.98 μA/mW as well as external quantum efficiency increased from 10.89% to 37.89% at a wavelength of 625 nm. These enhancements are ascribed to the laser-induced molecular realignment, reduced trap density, and enhanced charge transport path.

Oral pyogenic granuloma (PG) is a benign but very vascular lesion that causes discomfort and bleeding. Conventional surgical excision is effective but has a high recurrence rate and postoperative pain. Diode laser excision is a less invasive procedure that offers precise tissue removal and better hemostasis. Our Objective is to evaluate the safety and efficacy of diode laser excision for the treatment of oral pyogenic granuloma. A total of sixteen patients (mean age 39.3; age range 15 - 74 years; 11 males and 5 females) with de novo oral PG were enrolled and all lesions were removed under local anesthesia using a continuous 1.5 W 980 nm diode laser with minimal bleeding, without the need for sutures and a 0.5 mm safety margin was kept. Patients were evaluated at one week and three weeks after surgery and on postoperative days one and three. Wound healing, hemostasis, pain and satisfaction were all assessed on every visit. The excised tissues were confirmed histopathologically. The diode laser provided better control over intraoperative bleeding, as any small amount of bleeding was easily controlled. Pain settled rapidly, as the majority of patients were comfortable by day three and completely pain-free within one week. The healing process progressed quickly, with satisfactory to excellent results by one week and full recovery by three. Nearly all patients expressed high satisfaction at the last follow-up. Diode laser excision is a safe and efficient treatment for oral PG that provides excellent hemostasis, less discomfort following surgery, quick healing, and high patient satisfaction. These findings corroborate the reliable clinical results of diode laser excision in current standard treatment.

Laser-induced breakdown spectroscopy (LIBS) has been used to investigate the plasma generated from a silver target by the Nd:YAG laser system at a wavelength of 1064 nm. The plasma was produced at different laser pulse energies (500, 600, 700, and 800 mJ) to study the effect of laser energy on plasma parameters. The electron temperature (Te) was determined using the Boltzmann plot method, while the electron density (ne) was calculated using Stark broadening of the spectral lines. Moreover, other plasma parameters such as plasma frequency (fp), Debye length (λD), and Debye number (ND) have been evaluated. The results showed that the electron density increased from 3.11×10¹⁷ cm⁻³ to 5.32×10¹⁷ cm⁻³ with increasing laser energy, while the electron temperature increased from 0.64 eV at 500 mJ to 0.84 eV at 800 mJ. The plasma frequency also increased from 5.01×10¹² Hz to 6.55×10¹² Hz, whereas the Debye length decreased from 3.37×10⁻⁷ cm to 3.06×10⁻⁷ cm. The Debye number (ND) was greater than unity, confirming that the generated plasma satisfies the basic conditions of a stable ionized plasma. These results indicate that increasing laser energy significantly influences excitation, ionization processes, and overall plasma characteristics.

In this work, an optical fiber sensor was developed for magnetic field detection. Single-mode and multi-mode fibers were used based on two main processes: chemical etching using hydrofluoric acid (HF) and coating with Fe3O4 nanoparticles. The nanoparticle layer was deposited using pulsed laser deposition (PLD) with an Nd:YAG laser operating at a wavelength of 1064 nm and 70 pulses, achieving a thickness of 49.4 nm in the sensing region. This work demonstrates the use of Fe3O4 nanoparticles in the coating process through two different techniques within the optical fiber system. In the first technique, the nanoparticles were deposited as a solid coating via pulsed laser deposition (PLD), achieving a thickness in the nanoscale range of 40–60 nm, which provides an effective surface for interaction. In the second technique, Fe3O4 nanoparticles were used in the preparation of a magnetic fluid that acts as a liquid coating, forming a stable and magnetically responsive medium. This dual use of Fe3O4 in both solid and liquid coatings provides more effective interaction than the use of a single coating technique. The magnetic fluid was prepared by dispersing 5 g of Fe3O4 powder in 13 g of paraffin oil. The experimental results showed that increasing the etching time during the chemical etching process using hydrofluoric acid (HF) led to a reduction in the optical fiber diameter, accompanied by a decrease in the transmitted optical power. These results are consistent with previous studies, which have shown that the tapering process using hydrofluoric acid (HF) transforms a conventional optical fiber into a sensitive element capable of responding to external variations. Therefore, this approach provides a suitable way to improve fiber sensitivity and enables its use in magnetic field sensing applications.