Iraqi Journal of Laser

1

Study the Effect of PH Variation on the Particle Size of Sio2 Thin Films

Mohamed K. Dhahir

Pages: 1-8 English

Abstract

In this paper, SiO2 nanoparticles thin films were synthesised at different PH values of solution by sol gel method at fixed temperature (25oC) and molar ratio (R =H2O/precursor) of (Tetra Ethyl Ortho Silicate) TEOS as precursor at (R=1). The structure and optical properties of the thin films have been investigated. All thin films were tested by using X-RAY diffraction. All X-RAY spectrum can be indexed as monoclinic structure with strong crystalline (110) plane. The morphological properties of the prepared films were studied by SEM. The results indicate that all films are in nano scale and the particle size around (19-62) nm .The size of silica particles increases with increasing PH value of solution where both the rate of hydrolysis and condensation become faster and affect on the solubility of intermediate [Si (OC2H5)4-X(OH)X] and hence affect on the supersaturation of the nucleation process . Also the UV-visible study indicates that the absorption is minimum and transmittance is maximum at the visible range of the spectrum. Accordingly, the sample is suitable for antireflection coating such as solar cells.

2

Synthesis Characterization and Optical Properties of Nanostructured Zinc Sulfide Thin Films Obtained by Spray Pyrolysis Deposition

Rawaa A. Faris, Mohamed K. Dhahir

Pages: 9-12 English

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Abstract

In this work, nanostructure zinc sulfide (ZnS) thin films at temperature of substrate 450 oC and thickness (120) nm have been produced by chemical spray pyrolysis method. The X-Ray Diffraction (XRD) measurements of the film showed that they have a polycrystalline structure and possessed a hexagonal phase with strong crystalline orientation of (103). The grain size was measured using scanning electron microscope (SEM) which was approximately equal to 80 nm. The linear optical measurements showed that ZnS nanostructure has direct energy gap. Nonlinear optical properties experiments were performed using Q-switched 532 nm Nd:YAG laser Z-scan system. The nonlinear refractive index (n2) and nonlinear absorption coefficient (β) estimated for ZnS nanostructure for different intensities of laser beam. It has been found that n2 and β were decreased with increasing of intensity of incident laser beam. Also, two photon absorption has been observed. The first type of n2 was positive nonlinear reflective index and the second type of n2 was self-focusing nonlinear refractive index for the sample

3

Design High Efficient Reflectivity of Distributed Bragg Reflectors

Hayder T. Assafli, Ali H. Abdulhadi, Wail Y. Nassir

Pages: 13-18 English

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Abstract

Bragg Reflectors consist of periodic dielectric layers having an optical path length of quarter wavelength for each layer giving them important properties and makes them suitable for optoelectronics applications. The reflectivity can be increased by increasing the number of layers of the mirror to get the required value. For example for an 8 layers Bragg mirror (two layers for each dielectric pair), the contrast of the refractive index has to be equal to 0.275 for reaching reflectivity > 99%. Doubling the number of layers results in a reflectivity of 99.99%. The high reflectivity is purely caused by multiple-interference effects. It can be analyzed by using different matrix methods such as the transfer matrix method (TMM) which is the simplest method to study the characteristic of devices with different alternating layers.

4

Investigation of Nonlinear Optical Characteristics of the Multi-Wall Carbon Nanotubes (MWCNT's) Suspensions using Nonlinear Self-Diffraction of a Laser Beam

Munaf K. Khalaf, Fadhil A. Umran,

Pages: 19-23 English

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Abstract

Nonlinear diffraction patterns can be obtained by focusing a laser beam through a thin slice of the material. Here, we investigated experimentally the formation of the far field nonlinear diffraction patterns of cw laser beam at 532 nm passing through a quartz cuvette containing multi-wall carbon nanotubes (MWCNT's) suspended in acetone and in DI water at concentrations of 0.030.wt.%, 0.045 wt.%, 0.060 wt.%, and 0.075 wt.%. Our results show that increasing the concentration of both types of suspensions (MWCNTs in acetone and MWCNTs DI water) led to increase in the number of pattern rings which indicates an increase in their nonlinear refractive indices. Moreover, MWCNTs DI water suspension at a concentration of 0.075 wt. % was more efficient for achieving a high optical nonlinearity.

5

Creating a Conductive Surface of the PMMA by Laser Cladding with DWCNT and MWCNTS

Wala I. Rasool, Thaier A. Tawfiq

Pages: 25-34 English

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Abstract

This work studied the electrical and thermal surface conductivity enhancement of polymethylmethacrylate (PMMA) clouded by double-walled carbon nanotubes (DWCNTs) and multi-walled carbon nanotube (MWCNTs) by using pulsed Nd:YAG laser. Variable input factors are considered as the laser energy (or the relevant power), pulse duration and pulse repetition rate. Results indicated that the DWCNTs increased the PMMA’s surface electrical conductivity from 10-15 S/m to 0.813×103 S/m while the MWCNTs raised it to 0.14×103 S/m. Hence, the DWCNTs achieved an increase of almost 6 times than that for the MWCNTs. Moreover, the former increased the thermal conductivity of the surface by 8 times and the later by 5 times.

Articles in This Issue

Study the Effect of PH Variation on the Particle Size of Sio2 Thin Films

Abstract

Synthesis Characterization and Optical Properties of Nanostructured Zinc Sulfide Thin Films Obtained by Spray Pyrolysis Deposition

Abstract

Design High Efficient Reflectivity of Distributed Bragg Reflectors

Abstract

Investigation of Nonlinear Optical Characteristics of the Multi-Wall Carbon Nanotubes (MWCNT's) Suspensions using Nonlinear Self-Diffraction of a Laser Beam

Abstract

Creating a Conductive Surface of the PMMA by Laser Cladding with DWCNT and MWCNTS

Abstract