We report on a feature, that of hillock-shaped damage, formed on a glass surface by femtosecond pulses of $t_p\text{=180\hspace{0.17em}}\mathrm{fs}$ [full width at half maximum (FWHM) value] duration produced by a recording beam focus with energy of 5 nJ/pulse at 800 nm wavelength (the corresponding irradiance of about $\text{7.6\hspace{0.17em}}{\mathrm{TW/cm}}^2$ was evaluated for a 0.68 μm FWHM spot size). Single hillocks of 40–50 nm height were recorded reproducibly in single-pulse irradiation. Surface nanopatterning over a large, curved area (over $\text{200\hspace{0.17em}μ}{\mathrm{m}}^2)$ can be achieved by implementing a confocal surface curvature tracking method that utilizes the reflection of a supplementary cw-laser beam. The ablation pattern achieved by this method is consistent with that of a Coulomb explosion.

Filamentation of Bessel–Gauss pulses propagating in borosilicate glass is found to produce damage lines extending over hundreds of micrometers and consisting of discrete, equidistant damage spots. These discrete damage traces are explained by self-regeneration of Gauss–Bessel beams during propagation and are potentially applicable in laser microfabrication of transparent materials.

The effect of extreme water repellency, called the lotus effect, is caused by the formation of a Cassie–Baxter state in which only a small portion of the wetting liquid droplet is in contact with the surface. The rest of the bottom of the droplet is in contact with air pockets. Instrumental methods are often used to determine the textural features that cause this effect—scanning electron and atomic force microscopies, profilometry, etc. However, this result provides only an accurate texture model, not the actual information about the part of the surface that is wetted by the liquid. Here, we show a practical method for estimating the surface fraction of texture that has contact with liquid in a Cassie–Baxter wetting state. The method is performed using a set of ethanol–water mixtures to determine the contact angle of the textured and chemically equivalent flat surfaces of AlSI 304 steel, 7500 aluminum, and siloxane elastomer. We showed that the system of Cassie–Baxter equations can be solved graphically by the wetting diagrams introduced in this paper, returning a value for the texture surface fraction in contact with a liquid. We anticipate that the demonstrated method will be useful for a direct evaluation of the ability of textures to repel liquids, particularly superhydrophobic and superoleophobic materials, slippery liquid-infused porous surfaces, etc.

We report on quartz and glass cutting by a lateral scanning of femtosecond pulses (150 fs at 1 kHz repetition rate) of 800 nm wavelength at room and low pressure (5 Torr) air ambience. Pulses were focused by a low numerical aperture (NA≤0.1) objective lens. Optimization of fabrication conditions: pulse energy and scanning speed were carried out to achieve large-scale (millimeter-to-centimeter) cutting free of microcracks of submicron dimensions along the edges and walls of the cut. Cutting through out the samples of 0.1-0.5 mm thickness was successfully achieved without apparent heat affected zone. At low air pressure (5 Torr) ambience, redeposition of ablated material was considerably reduced. It is demonstrated that the damage on the rear surface was induced by the stress waves, which originated from the plasma ablation pressure pulse. The mechanism of femtosecond-laser cutting of transparent materials at high irradiance and the influence of stress waves generated by plasma plume are discussed.

The dephasing time $T_2$ of excitons and biexcitons is measured by femtosecond and picosecond four-wave mixing as function of frequency for different excitation intensities and temperatures. Their behavior is discussed in the frame of different scattering mechanisms. From this, the biexciton acoustic- and optical-phonon scattering cross sections are determined.

The eligibility of applying the Owens–Wendt approach to determining the free surface energy of liquid-repellent aluminum surfaces, with micro- and nanotextures formed by a femtosecond laser, was considered. This approach has been shown to be applicable using two essential parameters that can be derived from the graphs. The first is related to the fraction of the contact area between the liquid and the solid surface in the Cassie state. The second is related to the degree of intrinsic polarity of the surface material or the applied organic modifier. The presented interpretation was used to compare the liquid repellency of the obtained textures. A microtexture with a period of 60 μm and a groove width of 45 μm has been shown to be the most liquid repellent. Among the modifiers, 1H,1H,2H,2H-perfluoroctyltriethoxysilane was the most effective, and stearic acid was only slightly inferior, but promising in terms of cost and environmental friendliness. It was shown that spontaneous hydrophobization provided a contact angle with water up to 159°, but the stability of such textures was inferior to the considered modifiers.