دراسة الخواص البصرية والكهربائية لصبغات عضوية == Study of optical and electrical properties of organic dyes
Author name:
علي ستار جبار الصيمري
Supervisor name:
وليد علي حسين | فرات احمد مهدي
General topic:
Physics
Specific topic:
Laser Physics and Electro-optics
Degree:
Master
University:
University Of Basrah - College Of Education For Pure Sciences
Language:
Arabic
University location:
Basrah
First pages:
26T1683 - p.pdf
Abstract:
In this study, thin films of polyvinyl alcohol (PVA) doped with Orange G , Safranin O , and Crystal Violet dyes , have been prepared by using casting method after dissolving the dyes with distilled water .The linear optical parameters of the prepared thin films such as absorption coefficient (α) , extinction coefficient (k) , refractive index (no) and energy gap (Eg) , in addition to Urbach tails (Eu) , both real (εr) and imaginary (εi) parts of the dielectric constant , optical conductivity (σopt) , and electrical conductivity (σele) have been studied. The non linear absorption coefficient (β), non linear refractive index (n2) and the susceptibility of the third order (χ3) have been studied too .It is found that the absorption spectra of the prepared thin films are characterized by a clear absorption peaks in the visible range of the light spectrum . For Orange G two absorption peaks were appeared at the wavelengths (325 nm) and (490 nm) , where as one absorption peak is observed for each of Safranin O , and Crystal Violet at the wavelength (540nm) and (600nm) respectively. It is worth noting that the different concentrations of the dyes have an obvious traces on the absorption intensities of the thin films , which may be related to the extended Urbach tails as a result of increased dye concentration and (π - π*) transition .The estimated energy gaps gave an indication that an indirect allowed electronic transition take place and it is inversely slightly affected by the concentration of the dyes.The non linear optical properties for the prepared thin films were studied using Z - scan technique . Three different cases in which the materials are ; thedye solution consist of the dye dissolved in distilled water , the dye solution mixed with the polymer , and the dye doped thin polymer film , were studied using continuous wavelength (532 nm) solid state semiconductor laser type (SDL - 532 - 100T) .The results indicated that the calculated (β) and (n2) increases as a results of increase in the concentration for all the three mentioned cases . Defocusing due to thermal distribution through the samples which were accompanied with a changes in non linear refractive index were shown , that is , the samples behave like a thermal lens that distort the phase of the propagated beam in it .The (I - V) characteristics for all thin films give an indication of Ohmic behavior and the DC electrical conductivity (σele) increases as the temperature increase . The activation energies (Ea) were found to be decrease at higher dyes concentrations .
