Closed aperture z-scan technique using the Fresnel–Kirchhoff diffraction theory for materials with high nonlinear refractions

Self-diffraction and high nonlinear optical properties of carbon nanotubes under CW and pulsed laser illumination

“…We observed that the valley in the closed-aperture transmittance is reduced as shown in Fig. 8 and the curve is asymmetric which indicates a large nonlinearity [24]. A good agreement has been obtained between the experimental data (points) and the theoretical curve (solid line).…”

“…Therefore, for larger nonlinearities, simple z-scan set-ups and theories are not complete for nonlinearity characterization. In this condition, analysis of diffraction ring pattern is reliable and valid [24]. In other words, using another value of Δφ 0 between 25 and 50 in numerical curves of closedaperture z-scan, gives similar curve to what is shown in Fig.…”

“…[16] should be revised. When the nonlinear phase shifts increase rather than unite, the symmetrical shape of the closed-aperture curve disorients and the difference between the peak and the valley in the normalized closed aperture obeys a different relation [16,24]. For Δφ 0 (t) N 25, the difference between the maximum and minimum transmittance tends to a constant value and is not sensitive with the increase of Δφ 0 (t).…”

“…This simple model predicts different patterns [24] due to the interaction of either a convergent or a divergent Gaussian beam with either self-focusing or self-defocusing media. If the Gaussian beam is convergent at the sample place, the radius of the wave front curvature would be negative, and if the beam is divergent the radius would be positive.…”

Nonlinear Optical Tweezers As an Optical Method for Controlling Particles with High Trap Efficiency

“…Consequently, the nonlinear effect is very weak and then practically to enhance optical trap efficiency (OTE) it needs a high laser intensity [6]. Fortunately, there is a lot of organic dyes with high nonlinearity as Diclothane Polimetin [24] with n Dp ≈ 5.5 × 10 −8 cm 2 /W, Acid blue with n Ab ≈ 1 × 10 −10 m 2 /W [25], Mercurochrome with n Mer ≈ 1 × 10 −11 m 2 /W at laser wavelength of 532 nm [26], and Acid Green with n Ag ≈ 1 × 10 −11 m 2 /W at laser wavelength of 635 nm [27]. All mentioned organic dyes are not only in solvent, but can be also chemically accumulated in the glass plate with thickness below millimeter, which has been used to observe the nonlinear refraction as well as laser limiter [28].…”