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In this paper, titanium nitride nanoparticles were prepared in three methods, In the first method, titanium nitride nanoparticles were prepared by the Ball-mill method; in the second and third methods, the nanoparticles were synthesized by the sol-gel, and the co-precipitation methods. The samples were characterized by X-ray diffraction (XRD), UV-Vis spectroscopy, and scanning electron microscopy (SEM), for the study of structural, linear optical properties, and surface morphology study, respectively. The Z-scan technique was utilized to study the TiN nanoparticles nonlinearity. A change in nonlinear optical behavior with an increase in input pump power and concentration of the TiN nanoparticles was observed. Results showed that the TiN nanoparticles give new potentials in nonlinear optical applications. The nonlinear optical behavior of the TiN nanoparticles shifts from inverse saturation absorption to saturation absorption with increase of intensity.

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A wavefront sensor which takes advantage of the moiré deflectometry has been constructed for measuring atmosphere induced wavefront distortions. In this sensor a collimated laser beam propagates through turbulent atmosphere, then a beam splitter splits it into two beams and the beams pass through a pair of moiré deflectometers. Directions of the grating's rulings are parallel in each moiré deflectometer but are perpendicular in the two beams. Using a suitable array of lenses and mirrors two sets of moiré patterns are projected on a CCD camera. A suitable spatial filter removes the unwanted frequencies. Recording the successive moiré patterns by the CCD camera and feeding them to a computer, allow temporal fluctuations of the laser beam wavefront phase to be measured highly accurately. Displacements of the moiré fringes in the recorded patterns correspond to the fluctuations of two orthogonal components of the angle of arrival (AA) across the wavefront. The fluctuations have been deduced in successive frames, and then evolution of the wavefront shape is determined. The implementation of the technique is straightforward and it overcomes some of the technical difficulties of the Schlieren and Shack-Hartmann techniques. The sensitivity of detection is adjustable by merely changing the distance between two gratings in both moiré deflectometers and relative grating ruling orientation. This overcomes the deficiency of the Shack-Hartman sensors in that these require expensive retrofitting to change sensitivity. Besides, in the moiré deflectometry, the measurement is relatively insensitive to the alignment of the beam into the device. Hence this setup has a very good potential for adaptive optics applications in astronomy. Since tilts are measured in the Shack-Hartmann method at discrete locations, it cannot detect discontinuous steps in the wavefront. By this method discontinuous steps in the wavefront are detectable, because AA fluctuations are measured across the wavefront.

In this work, Silicon oxide (SiO2) nanoparticles, graphene oxide nanosheet (GO) and GO–SiO2 nanohybrid composites have been synthesized. The role of GO concentration in the starting solution was investigated and correlated to the morphological, structural and optical properties of the studied samples. The structural studies for nanohybrid composites showed that by increasing GO:weight ratio from 0.5 to 2.0, not only does the SiO2 crystalline phase change from cubic to orthorhombic, but the structure of GO also transformed to RGO. The related FESEM images indicate that GO sheets are well-covered by SiO2 nanoparticles with very small grain size and that the accumulation of nanoparticles on each sheet has a high density. Linear Optical measurements showed two optical band gaps of [Formula: see text][Formula: see text]eV and 5.3[Formula: see text]eV for SiO2 nanoparticles, and band gap value of 4.15[Formula: see text]eV for GO nanosheets, which it reduces to 3.3[Formula: see text]eV after formation of the nanohybrid composite with GO: SiO2 weight ratio of 2.0. The nonlinear optical properties of GO–SiO2 with different weight ratio are measured using Z-scan technique. The results showed that the nonlinear refractive index of SiO2 and GO nanoparticles and nanohybrid composite (0.5:1,1:1,2:1) ([Formula: see text]–[Formula: see text]) changed and has a negative sign. It was observed that the nonlinear refractive index changes in different ratios of compounds. Experimental results show that after the formation of the composite, the nonlinear refractive index shows a significant increase in the presence and effectiveness of the GO.