Observation of high nonlinearity in Bi doped BixIn35-xSe65 thin films with annealing

The present work demonstrates the impact of thermal annealing on the structural, linear, and non-linear optical characteristics of thermally evaporated BixIn35-xSe65 (x = 0, 5, 10, 15 at%) thin films. The prominent crystalline phases have been developed for all annealed films at 450 °C whereas the films remain amorphous at 350 °C annealing. The XRD and Raman analysis showed the phase transformation of Bi-doped films and new Bi2Se3 phases developed upon annealing at 450 °C. The phase transformation induced change increased the linear and nonlinear properties with great extent as seen from the UV–visible optical studies. The direct and indirect optical bandgaps decreased with annealing temperature and also with Bi % content due to the formation of surface dangling bonds near the crystallite sites. The static linear refractive index and high-frequency dielectric constants were increased with annealing. The third-order non-linear susceptibility and non-linear refractive index were found to be greatly influenced by annealing temperature and increased with bismuth content. The FESEM micrographs also showed the phase transformation and EDX analysis showed the composition. The results obtained from the materials showed the potentiality to be useful for photovoltaic and optoelectronic applications.

Study the Nonlinearity Characteristics of Organic-Semiconductor (CuPc) Prepared Via Pulsed Laser Deposition Technique with Different Thickness

The optical absorption spectrum, Photoluminesces, and non-linear optical properties for Copper Phthalocyanine (CuPc) thin films (150,300 and 450 nm) respectively have been investigated via pulsed laser deposition technique. The absorption spectrum indicted that there are two bands one in UV around 330 nm which called B-band and the second in Visible around 650nm which called Q-band. Photoluminescence spectrum related to deposit samples has been determined with different thicknesses. From closed and open aperture Z-scan data non-linear absorption coefficient and non-linear refractive index have been calculated respectively using He-Ne laser which have beam waist of (24.2 μm), wave-length of (632.8 nm) and Rayleigh thickness was 2.9 mm. Through dividing closed by open apertures, non-linear refractive index was calculated accurately. Finally, the study also showed the suitability of the deposited films as an optical limiter at the wavelength 632.8 nm.

A refractive index of a kink in curved space

The refractive index and curvature relation is formulated using the Riemann-Christoffel curvature tensor. As a consequence of the fourth rank tensor of the Riemann-Christoffel curvature tensor, we found that the refractive index should be a second rank tensor. The second rank tensor of the refractive index describes a linear optics. It implies naturally that the Riemann-Christoffel curvature tensor is related to the linear optics. In case of a non-linear optics, it implies that the refractive index is a sixth rank tensor, if susceptibility is a fourth rank tensor. The Riemann-Christoffel curvature tensor is still able to be formulated but with a reduction term. The relation between the (linear and non-linear) refractive index and (linear and non-linear) mass in curved space are formulated. Related to the Riemann-Christoffel curvature tensor, we formulate "the (linear and non-linear) generalized Einstein field equations". Sine-Gordon model in curved space is shown, where the Lagrangian is the total energy or mass of model. The mass of a kink (anti-kink) is shown, where it is associated with a topological charge. This topological charge is interpreted as a winding number. We formulate the relation between the (linear and non-linear) refractive index of the kink (anti-kink) and the topological charge-the winding number. Deflection of light is discussed in brief where the (linear and non-linear) angle of light deflection are formulated in relation with the mass (the topological charge, the winding number) of the kink (anti-kink).

Shape and size dependent nonlinear refraction and absorption in citrate-stabilized, near-IR plasmonic silver nanopyramids

The shape change from 2D nanoplates to 3D nanopyramids reversed the sign of non-linear refractive index,n2, from negative to positive one. Amongst nanopyramids, as edge length increases,n2increases linearly.