Synthesis, structural properties and nonlinear optical response of some aromatic thioamides in bulk vs. laser-processed films

Abstract Currently, the effects of nonlinear optics are important in almost all optoelectronic applications. Here, we present results on new, laboratory synthesized aromatic thioamides. Thin films with controlled thickness are subsequently deposited by matrix-assisted pulsed laser evaporation (MAPLE), on fused silica / SiO2, and silicon substrates / Si (100), with the aim of evaluating their nonlinear optical properties for potential optoelectronic applications. The concentration of the guest compound in the DMSO (dimethylsulfoxide) matrix used was 1% wt. At fluences ranging from 0.1 to 1 J/cm², a Nd:YAG laser (7 ns pulse duration, 4ω/266 nm, 10 Hz repetition rate) was used to irradiate the frozen target. The techniques involved in probing the morphology of the film surfaces are optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Spectroscopy-ellipsometry (SE) was used to investigate the optical properties of the thin films, and also the dependence of the refractive index with respect temperature was studied. The second harmonic generation (SHG) potential is assessed by using a femtosecond Ti:sapphire laser (800 nm, 60–100 fs pulse duration, 80 MHz), at 250 mW maximum output power, revealing the thickness of the films strongly influences the intensity of the SHG signal. An understanding of these effects combines the classical theory of light with the quantum nature of the energy levels in materials.