Generation of the second and third harmonics of femtosecond Cr: forsterite laser pulses in SiC/PMMA nanopowder films

Abstract

Second-and third-harmonic generation in silicon carbide (SiC) nanopowders embedded in a polymethyl methacrylate (P MMA) film are studied using nano-, pico-, and femtosecond laser pulses. Second-and third-harmonic generation processes are shown to allow the detection of absorptive agglomerates of nanocrystals in transparent materials and the visualization of optical breakdown in nanocomposite materials. Polarization of the third-harmonic signal is shown to be highly sensitive to the polarization of the pump field, permitting third-harmonic generation to be used as a probe for the anisotropy of nanocomposite materials. The second-harmonic signal, on the contrary, has no memory of the initial polarization state of the pump field and is, consequently, ideally suited as a measure of orientation-averaged nonlinearities of nanopowder materials. Second-harmonic yield, arb. un. Nanoscale nonlinear optics [1] unveils the fundamental aspects of light-nanostructured matter interactions and gives recipes for designing new materials and creating novel devices for laser physics, nonlinear optics, and ultrafast photonics. Nonlinear optics also offers equally elegant and convenient methods to understand many of fundamental properties of micro-and nanostructured matter [2,3]. Harmonic-generation and wave-mixing processes have been shown to offer new solutions in nonlinear microscopy. In particular, third-harmonic generation (THG) proved to be a very useful tool for a microscopy of biological objects [4,5] and plasmas [6]. It would be a challenging task to extend the ideas of nonlinear-optical imaging to nanoscale systems by applying harmonic-generation and wave-mixing techniques to the visualization of assemblies of nanocrystals and nanoparticles and analysis of nanocomposite materials.

Enhancement of two-photon absorption in anisotropic mesoporous silicon

“…Besides, the local-field inhomogeneity at a scale of the light wavelength results in enhancement of the nonlinear-optical response [6]. Analogous effect was found in experiments on THG in silicon carbide nanopowders embedded in a polymetil metacrylate [13].…”

Plasmon-enhanced nonlinear optical properties of SiC nanoparticles

“…Furthermore, the initial NLO properties of the SiC nanostructures can be significantly enriched due to defects, crystalline symmetry and shape distortions as well as due to any broken symmetry at interfaces. A variety of the NLO phenomena including second-and third-harmonic generation (SHG, THG), nonlinear refraction and the linear electro-optic effect have been mainly reported for SiC nanopowders and solid films with nano-SiC inclusions [12][13][14][15][16]. However, in comparison with commonly used nonlinear crystals, the reported NLO characteristics of the SiC nanostructures have to be enhanced.…”

Resonant laser-plasma excitation of coherent THz phonons under extreme conditions of femtosecond plasma formation in a bulk of fluorine-containing crystals

“…Therefore, in order to study the excitation and relaxation dynamics of coherent phonons under the plasma formation regime the nonlinear-optical method based on THG was used. In the standard pump-probe scheme [23,31] with polarization separation the channel of the third harmonic generated by the probe pulse was added [32]. Table 1.…”