Narrow Results

The results of recent studies on the optical limiting properties of BODIPY dyes at 532 and 1064 nm are described and compared. The optical limiting properties of novel 1,7-dimethyl-3,5-di-4-dihydroxyborylstyryl- and 3,5,7-tristyryl-1-methyl-BODIPY dyes were studied in CH₂Cl₂ and C₆H₆ and polystyrene thin films using the open aperture Z-scan technique at 532 nm with nanosecond laser pulses to provide an example of how the effective nonlinear absorption coefficient, the third order susceptibility, hyperpolarizability and limiting thresholds can be calculated.

The synthesis and characterization of a novel dibrominated 1,3,5-tristyrylBODIPY dye is reported, and its potential utility as a singlet oxygen photosensitizer and optical limiting material is assessed. The main spectral band lies in the therapeutic window, and there is a moderately high singlet oxygen quantum yield making the dye potentially suitable for use in biomedical applications and as an optical limiting dye at 532 nm. The optical limiting parameters are comparable to those reported previously for 3,5-distyrylBODIPYs, which suggests that mixtures of 3,5-distyryl and 1,3,5-tristyryl compounds that are formed in Knoevenagel condensation reactions could be used for this application. Theoretical calculations are used to assess the effect of 1,3,5-tristyryl substitution. A smaller red shift of the main spectral band is observed upon styrylation at the 1-position than is the case with the 3,5-positions due to there being smaller MO coefficients at this position, limiting the utility of this structural modification method for shifting the main BODIPY spectral band further into the therapeutic window.

Well-crystallized SrBi₂Nb₂O₉ (SBN) thin films with smooth surfaces (the root mean square roughness is about 4.550 nm over an area of 2×2 μm²) are fabricated on MgO (100) substrates by the pulsed laser deposition technique at 750 °C under the oxygen pressure of 30 Pa. The nonlinear optical properties of the films are studied by using a single beam z-scan with ns pulses at 532 nm. SBN thin films exhibit an excellent nonlinear optical response, with the real and imaginary parts of the third-order nonlinear optical susceptibility being 4.139×10⁻⁷ esu and 1.104×10⁻⁷ esu, respectively. These show that SBN ferroelectrics thin films have potential applications in nonlinear optics.

Based on the Z-scan technology, the nonlinear absorption characteristics, the nonlinear refraction characteristics of ZnO nanoparticles dimethylformamide (DMF) solution and ZnO nanoparticles ethanol solution have been studied under the nanosecond (ns) laser pulses and the picosecond (ps) laser pulses. The experimental results show that the third-order nonlinear effect of ZnO nanoparticles ethanol solution is stronger than that of ZnO nanoparticles DMF solution under the ns laser pulses, and the third-order nonlinear susceptibility coefficient of the ZnO nanoparticles DMF and the ethanol solution are |χ⁽³⁾| = 2.15 × 10⁻¹²esu, |χ⁽³⁾| = 8.12 × 10⁻¹²esu respectively. The third-order nonlinear effect of the ZnO nanoparticles ethanol solution is similar to the ZnO nanoparticles DMF solution under the ps laser pulses. The third-order nonlinear susceptibility coefficient of the ZnO nanoparticles DMF and the ethanol solution are |χ⁽³⁾| = 1.16 × 10⁻¹⁴esu, |χ⁽³⁾| = 1.15 × 10⁻¹⁴esu respectively and the optical nonlinearities of ZnO nanoparticles under the ns laser pulses are better than that of the ZnO nanoparticles under the ps laser pulses.