Narrow Results

Three- and four-photon nonlinear absorptions are reported by z-scan techniques in ZnS and 1% Mn²⁺ doped ZnS quantum dots (QDs) with 532 and 1064 nm radiations, respectively, obtained from a Q-switched Nd:YAG laser fundamental and its second harmonic radiation. The obtained maximum value of the 3PA coefficient in the doped ZnS QDs is ~10⁵ times that of bulk ZnS. Also, intensity-dependent saturation of 3PA has been observed and the measured experimental data are explained theoretically using a 3PA saturation model and the characteristic saturation intensity is estimated to be 0.92±0.04 GW/cm².

Nanoparticles of silver-embedded indium oxide thin films have been prepared on glass and silicon substrates. Silver concentration were 3 wt.% and 5 wt.% as measured by X-ray fluorescence. X-ray diffraction reveals that indium oxide of these samples remains amorphous even after pre-annealing at 400°C. The optical absorption of the samples manifests the surface plasmon resonance (SPR) phenomena, which varies with Ag content. The Ag nanoparticles radius was estimated with Mie classical theory by using the SPR data analysis. The nonlinear optical properties of films on glass substrate were investigated using z-scan technique. Under cw excitation the films exhibit large reverse saturation absorption and negative nonlinearities. The real and imaginary parts of third order susceptibility of the samples were measured and the imaginary part which arise from the change in absorption is found to be dominant.

Nanoparticle Lead sulfide was synthesized via simple chemical method and deposited on glass substrates at different substrate temperatures by thermal evaporation technique. The synthesized nanoparticle PbS was analyzed and confirmed by X-ray diffraction (XRD), Scanning electron microscopy SEM with EDX and thermogravimetry. The structural, optical, morphological and electrical properties of the deposited films were studied using XRD, UV-Vis, Raman, SEM with EDX, atomicforce microscopy AFM and Hall Effect measurements. The thickness of the deposited samples was measured using thickness profilometer. The Raman shift in the peak occurs toward lower energy with increasing substrate temperature deposited lead sulfide. The Z-scan study with open aperture was carried out at 532 nm using 5 ns laser pulse on the deposited films which shows that nonlinear absorption arises from saturable absorption process. The deposited PbS film exhibits p-type conductivity in Hall measurement.

Alloyed CdSe_0.3Te_0.7nanocrystals (NCs) were prepared by a thermochemical method using Thioglycolic acid (TGA) as a capping agent molecule. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) analysis demonstrated hexagonal phase NCs with an average size of around 2.5 nm. Synthesized NCs indicated a narrow band emission with a peak located at 561 nm. Nonlinear optical (NLO) properties of the CdSe_0.3Te_0.7NCs have been investigated by z-scan technique using Continuum Wave He–Ne laser. The nonlinear absorption coefficient and nonlinear refraction index were obtained in the order of 10^-2 and 10^-8, respectively. The results revealed that these NCs exhibit strong NLO properties effects such as self-defocusing and two photons absorption.

Optical nonlinearity of 4-dimethyl aminopyridinium dihydrogen phosphate (DMAPDP) was studied using continuous wave of diode pumped Nd:YAG laser (532nm, 50mW). The nonlinear refractive index, nonlinear absorption coefficient and nonlinear optical (NLO) susceptibility of the sample were found to be in the order of 10${}^{-8}$cm²/W, 10${}^{-3}$cm/W and 10${}^{-6}$ esu respectively. The observed self defocusing effect was used to demonstrate the optical limiting action at 532nm. Initially, XRD analysis showed that DMAPDP crystallizes in triclinic crystal system with centrosymmetric space group $P\overline{1}$. Thermal studies explored that the material undergoes an irreversible endothermic transition at 192${}^{\circ }$C which correspond to the decomposition of material. SEM image portrays the formation of nanoparticles with grain size in the range of 45–170nm. Hence 4-dimethyl aminopyridinium dihydrogen phosphate nanoparticles can be used as potential candidate for optical limiting applications.