Second harmonic Maker-fringe signals, measured for determination of second-order nonlinear coefficients of arrayed ZnO nanorods, were analyzed with an improved method. In this analysis, multiple reflections and interferences of fundamental and second harmonic waves were taken into account within ZnO nanorod layer, which thickness approaches the wavelength of the incident beam. Nanostructured semiconducting materials possess unique photonic and electronic properties due to their quantum size effects and field enhancements. Such materials, exhibiting large optical nonlinearities and fast response times, have been extensively studied for potential photonic applications [1,2]. Especially, ZnO is a wide bandgap (-3.4 eV) semiconductor, which can be grown with nanostructures using different techniques [2][3][4]. The well-known Maker-fringe technique, in which polarization-dependent second harmonic waves are detected in dependence of the incident angle of fundamental waves, is often used to evaluate second-order nonlinear optical coefficients of various materials. Unlike thick bulk materials, multiple reflections and FabryPerot interferences of fundamental and second harmonic (SH) waves can not be neglected more if the thickness of the sample is close to the wavelength of incident fundamental waves.In the present work, we estimated second-order nonlinear optical coefficients of three different ZnO nanorod layers by analyzing angular-dependent SH signals, which could not be fitted by conventional equations, with an improved method using propagation and density matrices. The sample was regarded as a multi-layered medium consisting of air, ZnO nanorods, ITO, glass substrate and air. Multiple reflections and interferences of reflected waves at each boundary surface were taken into account. The schematic of propagation of fundamental and SH waves in the multi-layered sample is depicted in Fig. 1.

Solid single-walled carbon nanotube (SWCNT)/silica composites were prepared by a sol-gel method. Their third-order susceptibilities were estimated by using z-scan technique at 532 nm and 1064 nm, respectively. The results reveal negative nonlinear refraction and saturable absorption, which magnitudes depend on kinds of used SWCNTs prepared by different techniques.