In this paper, texts were experimentally transmitted by pulse width modulation (PWM) using an underwater wireless optical communication system (UWOC) in a channel containing water of varying salinity as a result of changes in the concentration of sodium chloride (NaCl). Mathematical equations are used using a MATLAB program to compare theoretical and practical results at different slop angle (θ0). (NaCl) concentration was changed from (0% w/v) to (90% w/v) to achieve different salinity of water (i.e., from clear water to turbid water). A diode laser with a power of 30 mW and a wavelength of 532 nm has been employed in the transmitter. The experimental results show that the extinction coefficient or the overall attenuation C(λ) is equal to (0.083/m) in the water containing a low concentration of (NaCl) which is consistent with pure seawater. Additionally, the obtained optical power (PR) and the signal to noise ratio (S/N) decreases to (27.6) mW and (23.99) dB, respectively. Furthermore, it was found that the water had a maximum total attenuation C(λ) equal to (2.565/m) in the water containing a high concentration of (NaCl) which was compatible with turbid harbour water, as well as the received power and (S/N) decreases to (2.306) mW and (13.2) dB, respectively. The theoretical results were similar to the practical results when the slope angle of the target or detector relative to the optical transmitter was (zero).
The nanocrystalline structure of Lithium niobate (LiNbO3) was prepared and deposited onto substrate made of quartz by utilize pulse laser deposition technique. The effect of substrate temperature on the structural, optical and morphological properties of lithium niobate photonic film grown was studied. The chemical mixture was prepared by mixing the raw material (Li2CO3, Nb2O5) with Ethanol liquid without any further purification, at time of stirrer 3hrs but without heating, then annealing process the formed material at 1000C° for 4hrs. We characterized and analyzed the LiNbO3 nanostructure thin films by utilize Ultra-Violet Visible (UV-vis). The UV-vis measurements show that, when the substrate temperature increases, the values of transmission, absorption and energy band gap will decreased, but the values of reflection and refractive index will increased. That means the LiNbO3 thin film prepared at substrate temperatures 300C° give the best result for manufacture the optical waveguide.
The effect of laser wavelength on gold nanoparticle (Au NPs) fabrication is reported by using the laser ablation in the liquid method in the ethanol. The Pulsed Laser ablation in liquid technique of the gold target was ablated using an Nd:YAG laser nanopulsed nanosecond after that the investigation of the gold NPs was tested by the AFM (Atomic Force Microscopy), and the (XRD) X-ray diffraction. The results showed the characteristics of prepared NPs, depending on XRD, AFM. NPs obtained by 532 nm laser possess better properties than that achieved by 1064 nm laser according to the highest intensity of shorter wavelengths.
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