Cross-section profile of the nonlinear refractive index of Gorilla Glass obtained by nonlinear ellipse rotation measurements.

In this work we determined the influence of potassium-to-sodium ion exchange in the nonlinear refractive value (n2) of Corning's Gorilla Glass (GG). Due to the production process, GG has a rich potassium surface in comparison to the original sodium matrix glass. In order to determine the nonlinear cross-section profile, we have used a highly sensitive nonlinear elliptical rotation spatial measurement. Using a simple model, where the nonlinearity varies exponentially with depth, we observed that the value of the nonlinear refraction at the surface is about 22% greater than that of the matrix interior with a penetration depth constant of ∼50 µm.

Third-harmonic generation at the interfaces of a cuvette filled with selected organic solvents.

We report on the third-harmonic generation (THG) of tightly focused femtosecond laser pulses at the interfaces of a cuvette filled with organic solvents. Such a system presents four interfaces separating two materials of different refractive indices and third-order nonlinear susceptibilities where the THG takes place because the symmetry around the focus is broken. We selected two cuvettes (silica and B270 crown glass) filled with different organic solvents (acetone, chloroform, and dimethyl sulfoxide) in order to have a variety of interfaces with different linear and nonlinear optical properties. For some of the peaks, the self-focusing modifies the expected cubic power law dependence for THG and as a consequence the four peak profiles may be quite uneven. Although the THG is due to the electronic part of the nonlinear susceptibility, it can suffer from the influence of the self-focusing effect, a Kerr nonlinearity that can have both instantaneous electronic and slow nuclear contributions. This mixture of two distinct third-order nonlinear processes was never considered for such interfaces. All the THG signals could be understood by taking into account the self-focusing effect. Furthermore, the nonlinear refractive indices, n(2), and third-order nonlinear susceptibilities of the solvents, χ((3)), could be determined simultaneously by the THG signals using the cuvette walls as a reference.

Accurate measurement of nonlinear ellipse rotation using a phase-sensitive method.

We report on the accurate measurement of nonlinear ellipse rotation (NER) by means of a phase-sensitive method employing a dual-phase lock-in. The magnitudes and signs of pure refractive electronic nonlinearities of silica and BK7 were determined with this new method using 150 femtosecond (fs) laser pulses at 775 nm. Experimental and theoretical analyses of the NER signal were carried out and the results were compared to those obtained with the Z-scan technique.

Influence of self-focusing of ultrashort laser pulses on optical third-harmonic generation at interfaces.

We report on the third-harmonic generation of femtosecond laser pulses at interfaces. We measured slabs of different types of optical glasses and demonstrated that the asymmetric intensity profile observed for a tightly focused beam can be explained by self-focusing effects.

Correlation of clinical history with quantitative histology of lower extremity atheroma biopsies obtained with the Simpson atherectomy catheter.

The purpose of this study was to compare the histologic variability of atheromas resected from patients with various risk factors for vascular disease. Twenty-seven plaques obtained using the Simpson atherectomy catheter were studied. The results of this light and electron microscopic study indicate that patients with diabetes mellitus had increased numbers of smooth muscle cells in their plaques (P less than 0.05) and a trend toward denser, less fatty connective tissue matrix (P less than 0.07) when compared with non-diabetics, and that female diabetics had more smooth muscle cells in their plaques than male diabetics (P less than 0.05). The female patients, regardless of risk factors, had more smooth muscle cells in their plaques than male patients (P less than 0.004). Patients with poor distal runoff had more neovascularization of plaque (P less than 0.001). Tobacco use and age did not have statistically significant correlations with histologic patterns.