Anomalous behavior of the second and third harmonics generated by femtosecond Cr:forsterite laser pulses in SiC–polymer nanocomposite materials as functions of the SiC nanopowder content

Abstract

Femtosecond pulses of 1.25 µm Cr:forsterite laser radiation were used to study second-and thirdharmonic generation in silicon carbide nanopowders embedded in a poly(methyl methacrylate) (PMMA) film. Harmonic generation processes extend the analytical and sensing abilities of light-scattering techniques, including Raman spectroscopy, offering a convenient and efficient approach to the analysis of nanocomposite materials where nanoparticles tend to agglomerate, masking informative features in Raman spectra. The second-and third-harmonic yields are shown to display an anomalous, counterintuitive behavior as functions of the SiC nanopowder content in a polymer film. Whereas harmonic generation in polymer films with a high content of SiC nanocrystals is quenched by the absorption of agglomerating nanoparticles, the influence of absorption is less detrimental in nanocomposite films with a lower SiC content, leading to the growth of the second-and third-harmonic yields. Nanocomposite films with a lower SiC content are also characterized by a higher breakdown threshold, allowing pump pulses with higher fluences to be applied for more efficient harmonic generation.

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

“…The procedure employed to produce nanopowder films used in our experiments included two stages [25]. At the first stage, silicon carbide nanopowders were produced by laser synthesis from gaseous precursors.…”

Three‐photon‐resonance‐enhanced third‐harmonic generation for label‐free deep‐brain imaging: In search of a chemical contrast

“…From this increased absorption, however, there is still a long way to go to THG enhancement. Moreover, the relation between resonant absorption and THG enhancement is anything but trivial . The trouble is that the enhancement of THG susceptibility , provided in this setting by a three‐photon resonance at λ Hb (Figure b), comes at a penalty of increased loss of the third‐harmonic signal, which is subject to one‐photon‐resonance‐enhanced absorption (Figure b).…”

Advances in nonlinear optical spectroscopies: a historical perspective of developments and applications presented at ECONOS

“…Nanocomposites are of particular interest as they allow tailoring the properties of the materials for a given purpose. Konorov et al studied the second‐ and third‐harmonic generation in silicon carbide nanopowders embedded in a poly(methyl methacrylate) film using a femtosecond Cr:forsterite laser. A counterintuitive behavior was observed when the nanopowder content in the nanocomposite was varied, which could be explained taking quenching by the absorption of agglomerating nanoparticles into account.…”