Papers by morvarid rashidian
Iranian physical journal, Apr 23, 2014
Effects of low-intensity UV treatment on the optical constants of red BS dye-doped polymethyl met... more Effects of low-intensity UV treatment on the optical constants of red BS dye-doped polymethyl methacrylate (PMMA) film including refractive index, extinction coefficient, real and imaginary parts of dielectric constant, band gap energy, Urbach energy, and refractive index dispersion parameters are measured and calculated. Changes in optical constants mainly occurred in the UV-VIS range. Red BS dye, which is used as a UV absorber impurity in PMMA films, generated another energy band gap which was increased by UV treatment. Although some of the optical constants of PMMA are not changed noticeably by the treatment in this low range of UV radiation, our results confirm that polymeric changes such as chain scission and depolymerization can directly affect the optical constants of PMMA.
Optical and Quantum Electronics, Nov 16, 2018
The thermally induced optical bistability in prepared silver (Ag) nanosuspensions have been studi... more The thermally induced optical bistability in prepared silver (Ag) nanosuspensions have been studied experimentally, using Fabry-Perot and Mach-Zehnder interferometry methods. Two Ag nanosuspensions of different sizes were produced by different fluences of pulsed laser ablation method in distilled water. The pulsed Nd:YAG laser of 7 ns pulse width, 1064 nm wavelength and different fluences was employed to produce Ag nanosuspensions. Experimental observations were performed by an ultraviolet-visible-near infrared spectrophotometry. Structure and size of prepared Ag nanoparticles were diagnosed using transmission electron microscope images. Fabry-Perot and Mach-Zehnder interferometry methods were used to carry out the optical bistability process in prepared Ag nanosuspensions. In two considered interferometers, the obtained phase shifts of the hysteresis loops based on the optical bistability are inversely proportional to the nonlinear refractive index of samples and thickness of Ag nanosuspensions cells. Results indicate that the induced thermal effect of the optical bistability can be tuned by modifying parameters such as the nonlinear refractive index and applied interferometry methods. Hence, a desirable situation for the thermo-optical effects of the optical bistability can be easily realized in Ag nanosuspensions.
Fundamentals and Physical concepts of optical limiting (OL) phenomenon in nanometals have been re... more Fundamentals and Physical concepts of optical limiting (OL) phenomenon in nanometals have been reviewed in this manuscript.Two mechanisms of OL are based on nonlinear absorption and nonlinear refraction depends on the setup of the experiments. The effect of surface plasmon resonance (SPR) absorption of nanometals, as well as their size, shape, material, and concentration on their OL behavior are discussed in detail. Finally, OL phenomenon is investigated experimentally using gold and silver nanoparticles (NPs) suspensions in water, in low intensity regime. In addition, results based on the effects of laser intensity, aperture size, concentration, and size of Au and Ag NPs are presented.
Optical and Quantum Electronics, Aug 9, 2015
The linear and nonlinear optical properties of silver nanoparticles have been investigated experi... more The linear and nonlinear optical properties of silver nanoparticles have been investigated experimentally. Colloidal nanoparticle samples were synthesized by laser ablation at various fluences. The samples were characterized by linear absorption spectroscopy, transmission electron microscopy and dynamic light scattering methods. The behavior of nonlinear refractive index of nanoparticles was studied using the close and open Z-scan techniques by low power CW laser beam. Observation of asymmetrical configurations of the Z-scan curve indicates that nonlinear refraction occurring in the Ag samples is related to the thermo optical process. In addition, the observed optical limiting behavior is due to nonlinear refraction of samples arising from thermal lens formation under low power CW excitation. The optimum position for samples as the optical limiter based on self-defocusing effect is the valley point. When the illumination laser power is low, the self-defocusing effect is mainly dominated. Actually laser fluence variation during the ablation procedure leads to concentration variation of nanoparticles in suspensions which in turn affect the optical properties of samples. The dependence of the nonlinear properties on morphological parameters, metal concentration, and particle size have been explained by experimental results.
Nonlinear responses and optical limiting behavior of Basic Violet 16 dye under CW laser illumination
Optik, Dec 1, 2009
Nonlinear optical properties of Basic Violet 16 dye solution in water are studied employing diffe... more Nonlinear optical properties of Basic Violet 16 dye solution in water are studied employing different optical techniques. Experiments are performed using the second harmonic of a continuous Nd-Yag laser beam at 532nm wavelength and 100mW power. The effect of nonlinearity of Basic Violet 16 dye in broadening the laser beam is observed. The optical limiting behavior is investigated by measuring
Nonlinear Responses and Optical Limiting Behavior of Basic Violet 16 Dye Under CW Laser
Nonlinear optical properties of Basic Violet 16 dye solution in water are studied employing diffe... more Nonlinear optical properties of Basic Violet 16 dye solution in water are studied employing different optical techniques. Experiments are performed using the second harmonic of a continuous Nd-Yag laser beam at 532nm wavelength and 100mW power. The effect of nonlinearity of Basic Violet 16 dye in broadening the laser beam is observed. The optical limiting behavior is investigated by measuring
Optical Engineering, Jun 25, 2014
Fundamentals and Physical concepts of optical limiting (OL) phenomenon in nanometals have been re... more Fundamentals and Physical concepts of optical limiting (OL) phenomenon in nanometals have been reviewed in this manuscript.Two mechanisms of OL are based on non- linear absorption and nonlinear refraction depends on the setup of the experiments. The effect of surface plasmon resonance (SPR) absorption of nanometals, as well as their size, shape, material, and concentration on their OL behavior are discussed in detail. Finally, OL phenom- enon is investigated experimentally using gold and silver nanoparticles (NPs) suspensions in water, in low intensity regime. In addition, results based on the effects of laser intensity, aperture size, concentration, and size of Au and Ag NPs are presented.
Optical and Quantum Electronics, 2018
The thermally induced optical bistability in prepared silver (Ag) nanosuspensions have been studi... more The thermally induced optical bistability in prepared silver (Ag) nanosuspensions have been studied experimentally, using Fabry-Perot and Mach-Zehnder interferometry methods. Two Ag nanosuspensions of different sizes were produced by different fluences of pulsed laser ablation method in distilled water. The pulsed Nd:YAG laser of 7 ns pulse width, 1064 nm wavelength and different fluences was employed to produce Ag nanosuspensions. Experimental observations were performed by an ultraviolet-visible-near infrared spectrophotometry. Structure and size of prepared Ag nanoparticles were diagnosed using transmission electron microscope images. Fabry-Perot and Mach-Zehnder interferometry methods were used to carry out the optical bistability process in prepared Ag nanosuspensions. In two considered interferometers, the obtained phase shifts of the hysteresis loops based on the optical bistability are inversely proportional to the nonlinear refractive index of samples and thickness of Ag nanosuspensions cells. Results indicate that the induced thermal effect of the optical bistability can be tuned by modifying parameters such as the nonlinear refractive index and applied interferometry methods. Hence, a desirable situation for the thermo-optical effects of the optical bistability can be easily realized in Ag nanosuspensions.
Optics & Laser Technology, 2017
A facile in situ laser ablation synthesis of Copper nanoparticles on cotton fabric is reported in... more A facile in situ laser ablation synthesis of Copper nanoparticles on cotton fabric is reported in this paper. This synthetic method is a laser ablation based fabrication of Cu nanoparticles on cotton fabric for improved performance and antibacterial activity. The treated cotton fabric was characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, UV-Visible spectroscopic techniques and antibacterial counting test. Very good antibacterial behavior of treated fabrics achieved. This fabric can be used as medical and industrial textiles.
Optics and Photonics Society of Iran, Feb 15, 2014
In this manuscript; preparation of gold nanoparticles using the pulsed laser ablation of gold tar... more In this manuscript; preparation of gold nanoparticles using the pulsed laser ablation of gold target in water has been described. Optical absorption spectrum of nanoparticle suspensions in water has been observed and nanoparticles sizes have been analyzed by transmission electron Microscopy. The optical limiting measurement method is explained and obtained results are presented. The results of optical limiting experiments with CW ND YAG laser beam (wavelength 532nm) indicate linear response of samples when input power is below about 70 mW and nonlinear respons to large powers than this limitation. Results reveal that thermal nonlinear refraction index due to surface plasmon resonance is the main responsible for the limiting behavior of the metallic nanoparticles suspensions.
Optical and Quantum Electronics, 2015
The linear and nonlinear optical properties of silver nanoparticles have been investigated experi... more The linear and nonlinear optical properties of silver nanoparticles have been investigated experimentally. Colloidal nanoparticle samples were synthesized by laser ablation at various fluences. The samples were characterized by linear absorption spectroscopy, transmission electron microscopy and dynamic light scattering methods. The behavior of nonlinear refractive index of nanoparticles was studied using the close and open Z-scan techniques by low power CW laser beam. Observation of asymmetrical configurations of the Z-scan curve indicates that nonlinear refraction occurring in the Ag samples is related to the thermo optical process. In addition, the observed optical limiting behavior is due to nonlinear refraction of samples arising from thermal lens formation under low power CW excitation. The optimum position for samples as the optical limiter based on self-defocusing effect is the valley point. When the illumination laser power is low, the self-defocusing effect is mainly dominated. Actually laser fluence variation during the ablation procedure leads to concentration variation of nanoparticles in suspensions which in turn affect the optical properties of samples. The dependence of the nonlinear properties on morphological parameters, metal concentration, and particle size have been explained by experimental results.
Investigation of thickness and concentration effects on the nonlinear optical properties of yellow disperse doped PMMA
ABSTRACT
Iran -Effect of argon plasma treatment on the nonlinear optical properties of red lake doped comm... more Iran -Effect of argon plasma treatment on the nonlinear optical properties of red lake doped commercial PVC film is studied employing different optical techniques. PVC films were exposed to low pressure plasma from 5 to 15 minutes. Experiments were performed using the second harmonic of a continuous Nd-Yag laser beam at 532 nm wavelength and 20 mW power. The optical bleaching behavior of samples was investigated by measurement of transmission through them. For all pristine and plasma treated samples optical bleaching started at laser beam power of 3.5 mW. The nonlinear refractive index and two photons absorption coefficient of plasma treated samples were measured using Z-scan method. Experimental results show that real and imaginary parts of nonlinear susceptibility decrease with increasing the time of treatment.
Journal of Theoretical and Applied Physics, 2014
Effects of low-intensity UV treatment on the optical constants of red BS dye-doped polymethyl met... more Effects of low-intensity UV treatment on the optical constants of red BS dye-doped polymethyl methacrylate (PMMA) film including refractive index, extinction coefficient, real and imaginary parts of dielectric constant, band gap energy, Urbach energy, and refractive index dispersion parameters are measured and calculated. Changes in optical constants mainly occurred in the UV-VIS range. Red BS dye, which is used as a UV absorber impurity in PMMA films, generated another energy band gap which was increased by UV treatment. Although some of the optical constants of PMMA are not changed noticeably by the treatment in this low range of UV radiation, our results confirm that polymeric changes such as chain scission and depolymerization can directly affect the optical constants of PMMA.
Effect of concentration on the plasmonic absorption and optical nonlinearity of gold nanoparticles
Optical Engineering, 2012
ABSTRACT
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Papers by morvarid rashidian