Search

Synthesis and measurements of third-order optical nonlinearity and optical limiting of conducting copolymers of aniline are presented. Single beam z-scan technique was employed for the nonlinear optical studies. Continuous wave He–Ne laser operating at 633 nm was used as the source of excitation. Copolymer samples exhibited reverse saturable absorption (RSA) process. The nonlinear refraction studies depict that the copolymers exhibit self-defocusing property. The estimated values of β eff , n 2 and χ (3) were found to be of the order of 10 −2 cm/W, 10 −5 esu and 10 −7 esu respectively. Self-diffraction rings were observed due to refractive index change when exposed to the laser beam. A good optical limiting and clamping of power of ∼0.9 mW and ∼0.05 mW was observed. Therefore, copolymers of aniline emerge as a potential candidate for photonic device applications. [ABSTRACT FROM AUTHOR]

Abstract: We report the investigations of thermally induced third-order nonlinear optical and optical limiting characterizations for various concentrations of acid blue 40 dye in N,N-Dimethyl Formamide, studied by employing z-scan technique under cw He–Ne laser irradiation at 633 nm wavelength. The samples exhibited nonlinear absorption and nonlinear refraction under the experimental conditions. For lower concentration, the samples display both saturable absorption (SA) and reverse saturable absorption (RSA); whereas with increase in concentration, RSA behaviour prevails. The estimated values of the effective coefficients of nonlinear absorption β eff, nonlinear refraction n 2 and third-order nonlinear susceptibility χ (3) were found to be of the order of 10−2 cm/W, 10−4 esu and 10−6 esu respectively. Multiple diffraction rings were observed when the samples were exposed to laser beam due to refractive index change and thermal lensing. The effect of concentration and the laser intensity on the self-diffraction ring patterns was studied experimentally. The acid blue 40 dye also exhibited strong optical limiting properties under cw excitation and reverse saturable absorption is found to be the dominant nonlinear optical process leading to the observed nonlinear behaviour. [Copyright &y& Elsevier]

Abstract: We present the synthesis and results on the third-order optical nonlinearity and optical limiting properties of Polyaniline and Poly (o-toluidine) studied in N,N-Dimethyl Formamide solution using a single-beam z-scan technique. Experiments were performed using continuous wave He–Ne laser operating at 633nm wavelength as an excitation source. The samples exhibit absorption and refraction nonlinearities. The negative sign of the nonlinear refractive index n 2 indicates that both materials exhibit self-defocusing optical nonlinearity. The nonlinear refractive index n 2, the nonlinear absorption coefficient β eff and the third-order optical susceptibility χ (3) were determined and found to be of the order of 10−7 cm2/W, 10−2 cm/W and 10−7 esu respectively. The FTIR and UV–visible characterization spectra confirm the expected molecular structure of the polymers. Multiple diffraction rings were observed when the samples were exposed to laser beam. The appearance of rings is due to the refractive index change and thermal lensing. The polymer samples with different concentrations exhibits strong optical power limiting under continuous wave laser at the experimental wavelength. Reverse saturable absorption is the dominating mechanism for the observed absorption nonlinearities. [Copyright &y& Elsevier]