Concise multigram-scale synthesis of push-pull tricyanofuran-based hemicyanines with giant second-order nonlinearity: an alternative for electro-optic materials.

Highly stable and highly soluble push-pull heptamethine hemicyanines based on the tricyanofuran electron-accepting group can be prepared on a 15 g scale. The compounds display giant second-order nonlinear figure of merit, µß of up to 31,000×10(-48) esu, and lead to a poled material with a second-order nonlinear response, r33 of 90 pm V(-1) at 1.06 µm.

Suppression of parasitic lasing in high energy, high repetition rate Ti:sapphire laser amplifiers.

Transverse parasitic lasing is well known for limiting the signal gain and the pulse energy that can be extracted from Ti:sapphire petawatt amplifiers. We have developed a technique for suppressing these parasitic lasing modes based on perfect refractive index-matching liquid doped with a broad-bandwidth absorber to suppress the transverse lasing while ensuring proper heat removal from the Ti:sapphire crystal. The 800 nm laser output with a bandwidth of 41 nm (FWHM) and peak energy of 22.7 J at a repetition rate of 1 Hz is demonstrated.

Photochromic compounds as optical limiters in the nanosecond time range: the example of mercury dithizonate complex.

Although being an efficient photochromic compound which absorbs in the blue in its stable form and in the orange in its photoactivated form, the mercury dithizonate complex is shown to be a poor optical limiter for nanosecond laser pulses at the wavelengths where both isomers absorb. Optical limiting effect, which is a consequence of reverse saturable absorption due to the photoactivated form, is demonstrated to be weak because of the back photobleaching of this form, which is important all the more as the laser intensity is high. Numerical integration of the spatiotemporal evolution of the laser beam intensity across the solution helps the understanding of the respective roles of the laser fluence and pulse duration. Finally, we draw the conclusion that photochromic compounds can only be used as optical limiters if the time constant for the back photochemical reaction is slow compared to the pulse duration.