In this article, Au nanoparticles in polyvinylpyrrolidone (PVP) solution were prepared by gamma radiation at different concentrations. The solutions were irradiated at doses of 50 kGy for making different sizes. The average sizes of particle in the prepared samples were measured using the nanophox machine. A dual-beam mode-mismatched thermal lens (TL) method was used to investigate the effect of thermal diffusivity of samples. The TL measurement was carried out using a green diode laser (wavelength 532 nm, 60 mW) and a He-Ne laser (wavelength 632.8 nm, 0.5 mW) for excitation source and probe beam, respectively. The results showed that the thermal diffusivity of samples enhances with the growth of particle size and density of solutions. This increment can be attributed to phonon scattering at interface of particlesliquid and contact between the nanoparticles and surrounded liquid.
First, this study obtained the fields of an Airy beam (AiB) with optical vortex (OV) for a Fourier transform (FT) system and a fractional Fourier transform (fractional FT) system; thereafter, their intensity and phase patterns were simulated numerically. The splitting on each line of the phase pattern indicates the position of an OV. The results show that the OV position will change when the power of the fractional FT (p) changes. Moreover, the uniformity of the spot beam disappears for the beam with OV. Further, the characteristics of an AiB such as number, width, height, uniformity of the spot beam and the effective beam size will change when there is a change in the values of p and z.
In this study, we investigated the airy, cos-airy and cosh-airy beam lasers with optical vortex. Then, taking into account the Fourier transform, we examined and compared the propagation of these beams in a strong nonlinear system. The results indicated that by changing the input power p0 and the parameters b and the propagation length, the location of optical vortex displaces. It was shown that nonlinearity is one of the parameters that control optical vortex in optical systems used in these types of lasers. An important property in these beams is their direction variation due to the change in the mentioned parameters, which can be used in applications such as beam switching.
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