Measurement of Non-Linear Optical Absorption of PVC/TiO2 Nanocomposite via Z-Scan Technique for Optical Limiting

Abstract

This research focuses on PVC/TiO2 nanocomposites in the form of thin films in order to expand our understanding of photonics technology. For fabrication of the thin films, the casting method was used with nanocomposites composite were developed by mixing TiO2 nanoparticles with Polyvinyl Chloride (PVC) as the polymer matrix. The absorbance parameters were determined using spectral analysis, and the linear absorption coefficient was computed. A single beam Z-scan technique was used to evaluate the nonlinear refractive index and nonlinear absorption coefficient via a CW diode pumped solid state (DPSS) laser (Coherent Verdi-V5, 532 nm) was employed as the excitation laser at 50mW. Peak absorption was detected at 280 nm with increasing absorption observed as the proportion of TiO2 nanoparticles increased. The nonlinear absorption coefficient was found at (0.5342, 1.3585,1.5999, and 0.0253) 1????10?5 cm/W. All of the sample morphology resulting poor structure which then affect the NLO absorption of the materials. However, with the positive value of NLO absorption, they appear to be promising candidates for optical limiting applications.

Introduction

I. INTRODUCTION

Nonlinear optics (NLO) is a fascinating branch of physics that investigates the subtle interaction of light and matter that extend beyond the limits of linear optics. Over the years, researchers have discovered a wealth of nonlinear optical phenomena, such as sum and difference frequency creation, dynamic amplification, and four-wave mixing [1]. Each finding added to our understanding of light-matter interactions and creating opportunities of optical phenomena to investigate. Another area of study is the development of new nonlinear optical devices and components. Efforts are being made to design and manufacture compact and efficient nonlinear optical devices such as frequency converters, optical switches, and optical limiting [2]. These developments are intended to improve the operation of existing optical systems while also setting the way for future advances in technology.  On the other hand, polymer materials have come to be as flexible and potential nonlinear optics (NLO) choices. Polymer material development has made significant progress in recent years. It offers various interesting qualities, including low cost, simplicity of production, flexibility, and tunability of properties [2]. These features make polymers highly desirable for a variety of applications, including optics and photonics. Furthermore, doping polymers with suitable substances improves their nonlinear optical characteristics even further [3]. Doping can change the refractive index, increase nonlinear susceptibility, and improve polymer matrix stability [2,4].

 As be mentioned before, NLO has been reinvented by nanoparticle materials, which provide remarkable manipulation of light-matter interactions at the nanoscale. Nanoparticles act as doping agents in NLO materials, improving their nonlinear optical characteristics [5]. One can control the properties and responses of the composite material by including nanoparticles into host materials. This process results in increased nonlinear effects, such as higher nonlinear susceptibility and improved optical response [5].Thus, the use of nanoparticles as doping agents into polymer matrices has proven useful in modifying and improving the nonlinear optical characteristics of composite materials which would benefits NLO application such as optical limiting and optical switching.

II. MATERIALS AND METHODS

To begin, the 80mg of PVC supply by Sigma-Aldrich were added in 1.0 mL of tetrahydrofuran (THF). The magnetic stirrer with angular velocity of 400 rpm and timed for one hour at room temperature was used to help dissolve and prevent agglomerates. The PVC/THF solution was deduce a neat clear solution. Second, the titanium dioxide (TiO2) acquired also from Sigma-Aldrich. Nanoparticles (size 13 nm) in varied quantities (0, 5, 10, and 15) wt% were introduced slowly to a PVC/THF combination. The solution then, undergo stirrer process with the same set up for 2 hours until it achieved a satisfy homogenous solution. 

Lastly, the solution was poured consistently on a glass petri dish and leave the sample one day at room temperature for it to dry. After a day, the film was readily removed and the thin film of pure PVC and nanocomposites (PVC/TiO2) of varying concentrations were obtained.

The morphology of the samples was studied using scanning electron microscopy (SEM) brand JSM-5510LV, JEOL. The samples were set up inside the SEM chamber and exposed to a focus electron beam voltage of 5kV at 500 ????m. ImageJ analysis software was also used to determine the thickness of the samples [6]. The linear transmittance spectra of the samples were also examined with a UV-VIS-NIR spectrophotometer from SHIMADZU CORP UV-3600 Plus  . A CW diode pumped solid state (DPSS) laser (Coherent Verdi-V5, 532 nm) was employed as the excitation laser at 50mW. Two silicon amplified photodetectors (PDA55, Thorlabs) were used in the setup. The material sample was first placed at the focal plane of a lens system and was mounted into a precision motorized stage (LTS-300, Thorlabs) with jog step of 300 mm. The sample was then scanned along the axial direction with a focused laser beam. The focused laser was split by a 50:50 beam splitter after passed through the samples and were detected by both detectors. One of the pair of photodetectors was positioned after an aperture or closed z-scan which will be used to study the mechanisms that result in nonlinear refraction, whereas the other was positioned in front of a lens or open z-scan which will be sensitive to the nonlinear absorption reaction. Both of information was recorded by oscilloscope.

III. RESULTS AND DISCUSSION

In this study, the morphology observation for PVC/TiO2 of different concentration are retrieved. SEM images of all four PVC/TiO2 nanocomposites via SEM machine at a voltage of 5 kV. SEM micrographs of PVT0, PVT5, PVT10, and PVT15 samples at a 500 ????m scale are shows in Figure 5. Visual observation demonstrates that pure PVC thin film and PVC/TiO2 thin films with (5,10, 15) wt% concentration shows higher surface roughness. Based on PVT5, PVT10 and PVT15, the nanofillers are seem dispersed unequally in the host material. A rise in surface roughness could suggest a change in the material's morphology and a smooth and uniform surface, as in thin films is much more desirable for achieving maximum transmission and reflection of material towards [6] light which later would affect the NLO absorption response.

Conclusion

The current study proposes a investigation framework for PVC/TiO2 nanocomposite by studied and measuring upon nonlinear absorption properties. The prepared samples unfortunately did not met the basic requirements for thin film surfaces. However, the data retrieved still be important to study upon the affect morphology structure toward laser. The current work has also demonstrated of using Z Scan Technique in obtained the NLO properties. The technique approach yielded results that were quite similar to those obtained by others researcher. The PVC/TiO2 can be consider as good candidate for optical limiting due to the positive values of nonlinear absorption.

References

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Copyright

Copyright © 2023 Muhammad Arif Bin Jalil. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.