Optical Properties for Thin Film of Coumarin 334 Organic Laser Dye doped with PVA Polymer and Al 2 O 3 Nanoparticles

Background: In this work, the optical properties for thin film of Coumarin 334 organic laser dye doped with PVA polymer and AL 2 O 3 nanoparticles are determined at different concentrations, dissolved in ethanol solvent. Methods: Solutions at concentration (10-4 M) from coumarin (334) dye in ethanol solvent at Different concentrations from dye (1, 3, 5, and 7) ×10 -5 M were prepared. Results: The AFM measurements show that the grain size, root mean square and roughness belong to the surface of the thin films rises with thickness rise for thin films . It has also increased the absorbance due to the increase in concentration. Conclusion: By using Gaussian beam from CW pulsed laser at 457 nm, we used Z-scan to study the nonlinear optical properties. The nonlinearity of thin film highly excels the pure dye solutions.


INTRODUCTION
An organic dye laser uses various lasing métier.These media can be in different states, namely liquid state, gas state, and solid state.Whatever the state of the dye, they all show a characterized feature: It is the absorption range within the visible light.However, this characteristic appears in the organic dyes when they have extra conjugate units connected to the bipartite [1].These organic molecules are active so that they can be easily dissolved in solvents or they can be integrated into a solid matrix.Furthermore, these molecules envisage their maximum power in the liquid and solid states as lasing media [2].One of the most important classes of laser dyes is coumarin.The 7-position of coumarin laser dyes contains a potent electron-donating group, either an amino (-NR2) or hydroxyl (-OH).Thus, Coumarin dyes can be used to cover a large adjustable range of (420 to 580 nm).Some of the most effective laser sources employ coumarin dye [3][4][5].These compounds are dissolved in an organic solvent and used in dye lasers.They often have a strong absorption band [6].Depending on their chemical properties, laser dyes can be classified into various classes such as xanthenes, coumarin, and pyrromethene cases [7,8].A dye gets its color from the attendance of a chromophore group color [2].Such dyes can also be used in advanced photonics, fiber optics, optical limiting and optical amplifiers.The practical application of these dyes is the protection of human eye and sensors against laser output.Hence, these polymer-doped dyes are crucial [9].With increasing particle size, the ratio of surface atoms increases, changing the material's physical and chemical characteristics [10].
Nanotechnology is one of the best well-liked branches of polymer science and technology.This region frequently promotes novel material behavior.The mechanical, optical, electrical, and magnetic properties of nanocomposites at small nano-filler concentrations have sparked an increase in demand for nanoparticles implanted in polymer ground (1-10%) [11].

MATERIALS AND METHODS
One of the faviourte lasing dyes in the blue-green spectral region is the coumarin and related members.For instance, their quantum emission is very high which can be invested in different scientific and technological aspects.Coumarin and its derivatives also apply in coloring and non-linear optics because these molecules offer fluorescence property in the UV as well as the visible regions [12].Molecular formula C17H17NO3 as shown in Figure (1).Solutions at concentration (10 -4 M) from coumarin 334 organic laser dye in ethanol solvent are prepared.The powder is weighted by using an electronic balance type (BL 210 S, Germany), having a sensitivity of four digits.Different concentrations from each dye (1, 3, 5, and 7)×10 -5 M were prepared according to the following equation [2]: The above equation shows the weight of the dissolved material (W in g), molecular weight (Mw in g/mol), volume of the solvent (V in ml), and concentration (C in M).Then, the newly formed solutions are made thinner according to [13]: Where C1 and C2 are the primary and new concentration, respectively, V1 is the volume before dilution, and V2 is the volume after dilution.

RESULTS AND DISCUSSION
Figures (2and 3) show 2-D and 3-D images of AFM for thin films coumarin (334) doped with (PVA )polymer and (Al2O3) nanoparticles at (10 -3 ) M respectively.Table (1) states the average grain size that form the thin films.We have found that the root mean square and size grain and roughness belong to the surface of the thin films rises with thickness rise for thin films coumarin (334) doped with PVA polymer and (Al2O3) nanoparticles [14].Absorbance spectra of coumarin organic laser dye at different concentrations (1, 3, 5, and 7) ×10 -5 M in ethanol solvent are observed in wavelengths starting from 190 nm to 1100 nm.We have used UV-visible spectrometer with the following detail.It is Japanese Aquarius 7000 spectrometer from Optima company.Further, the measurements are performed at room temperature.These finding were illustrated in figure (4).From these Figures we can observed that absorption spectrum of coumarin (334) solution has a wide peak over wavelengths from 328 nm to 530 nm.It has also increased the absorbance due to the increase in concentration which produces a high number of moieties pre volumetric part.This is affect the energy state, as well as increasing of linear absorbance index and refractive index and .The results are in consistent behavoiur compared to Beer-Lambert law speculations [15].
The linear absorbance spectra of coumarin (334) dye nano films along different concentrations that also doped with PVA and (Al2O3) nanoparticles are shown in Figure (5).
The absorption peaks obtained here had moved to the red region when we added PVA and Al2O3.This shift obtain due to electronic and vibrational states of interfacial molecules, which is lead to increasing absorption for all samples of nanocomposites, this is suggested to take place because of the excitations of high occupation molecular orbital (HOMO) electrons to the lowest inoccupation molecular orbital (LUMO).We also use closed-and opened-aperture to measure the Z-scan for nonlinear refractive and absorption coefficients (n2) and (β), respectively.The experiment is performed under 457 nm and 84 mW power.The obtained results of Z-scan are shown in figure 6 and 7.These normalized transmittances are measure as a function of distance of coumarin 344 dye doped with PVA polymer and (Al2O3) NPs dissolved in ethanol  2) from this Table we show that the values of nonlinear parameters (n2 and β) are increased with increasing the concentrations, as omit due to its repetition the values of linear parameters (αo and no).This is due to increasing number of molecules per volume unit at high concentrations.