Yu. I. Pestov

Plasmon-polariton surface modes and nanostructuring of semiconductors by femtosecond laser pulses

This paper analyzes the published experimental data on the surface breakdown of semiconductors as a result of the action of a series of pulses of polarized femtosecond laser radiation, accompanied by the formation of regular and disordered micro- and nanostructures. The detected features of the ordered breakdown of transparent and opaque semiconductors and insulators are explained in terms of an extended universal polariton model of laser-induced breakdown of condensed media, including the excitation and interference of cylindrical surface plasmon-polaritons.

Controllable grain-boundary displacement during recrystallization and the microrelief of a titanium surface induced by laser radiation pulses

When multipulse laser-induced recrystallization of a titanium surface occurs under the action of polarized radiation, grain growth is detected, associated with the polarization direction of the radiation. An explanation of the observed phenomenon is given, based on the effect of electron entrainment by surface plasmon-polaritons excited at the grain boundaries.

Sensors and inverted resonance on surface plasmons in palladium

The behavior of the resonance curve for surface plasmons in the Kretschmann geometry for palladium is theoretically studied. The existence of inverted resonance in the near-IR region is detected for a thin film of palladium. It is shown that a broadening of the resonance is observed as the frequency of inelastic collisions of electrons in the metal increases and the plasma frequency decreases. Such behavior of the resonance, associated with variation of the optical constants of the metal, can be used in hydrogen sensors based on palladium.

Study of the temperature dependence of the absorbance of platinum by measuring the damping of a surface electromagnetic wave and the nature of a squeezed wave

The temperature dependence of the damping coefficient alpha of a surface electromagnetic wave (SEW) on a platinum mirror has been experimentally measured. The SEW was excited by laser radiation (λ=10.6 µm) on a diffraction grating from which the first order of diffraction propagated along the surface of the mirror. In the temperature range 20-110 °C, the temperature coefficient of damping of the SEW is obtained as β=dα/dT=(18±2)10−4 cm−1 °C−1. It is obtained from the data of these measurements that dA/dT=2.7×10−5 °C−1, where A is the absorbance of platinum. At the same time that the SEW was excited, excitation of a volume near-surface wave (NSW) on the diffraction grating was observed, propagating from the grating at an angle of 2.5° to the surface of the mirror. It is shown that the appearance of an NSW, also called a squeezed wave, is associated with divergence of the laser radiation.

Formation of relief gratings and refractive-index gratings on quartz glass under the action of a the radiation of a TEA CO2 laser*

This paper discusses how the profile of the residual surface relief of quartz glass in an irradiation spot depends on the number of active pulses of plane-polarized laser radiation with wavelength lambda = 10.6 µm. Based on experimental data, it is shown that an important role in the mechanism for forming periodic structures is played by the structural change of quartz glass subjected to melting and the associated change of its refractive index. Refractive-index gratings are detected in the near-surface layer of the glass in the total absence of periodic surface relief. When the radiation is normally incident, the period of the relief grating lies within the limits 8.9-9.1 µm, while the refractive-index grating lies within the limits 7.9-8.9 µm. These results agree with the model that explains the formation of the spatial modulation of radiation close to the surface of glass by the interference of the incident wave with surface phonon-polaritons.

Temperature dependence of the damping of a surface electromagnetic wave on nickel

The temperature dependence of the damping coefficient of a surface electromagnetic wave on nickel has been experimentally determined. The surface wave was excited by the radiation of a CO2 laser on a diffraction grating mechanically ruled on the surface of the sample. The thermal damping coefficient of the wave is obtained in the temperature range of interest. The data of these measurements are used to compute the temperature coefficient of the absorbance of nickel. The angular radiation distribution was measured in a bulk near-surface wave whose excitation was observed at the same time as the surface wave. It is shown that the excitation of the near-surface wave is associated with the divergence of the laser radiation, while the supplementary maxima in the distribution are associated with the finite width of the grating.

Laser-induced formation of conical bumps on the surface of superrefractory metals

The formation of conical bumps on W, Ta, and Mo surfaces as a result of irradiating them with a laser pulse in an atmosphere of air, nitrogen, or helium and in vacuum have been experimentally studied at an irradiation-energy density above the melting threshold but below the blowout threshold of the melt from the irradiation zone by vapor pressure. A strong dependence of the bump height on the composition of the gaseous atmosphere is detected. The minimum radius of curvature of the tip of 0.5μm and a tip angle of the conical bump of 60° were observed on molybdenum for a bump height of 19μm above the original surface level. It is shown that the regularities of formation of the conical bumps on the metals are associated with the final contact angle of wetting of the solid phase by its melt and with the dependence of the contact angle on the composition and chemical activity of the atmosphere. A model has been constructed of the formation of a conical bump during the crystallization of a limited bath of the melt.

Features of the relief formed on the surface of quartz glass under the action of a moving beam of a cw CO2 laser

This paper discusses the surface-relief profiles of quartz glass after it is acted on by the moving focused beam of a cw CO2 laser. The results are explained well in terms of a thermocapillary mechanism of relief formation, if the temperature coefficient of surface tension of the glass changes sign as the temperature increases. The phenomenon whereby a flat floor is formed in the microchannel that remains after the glass solidifies is detected and qualitatively explained.

Peculiarities of the dynamics of the relief induced by two-beam laser interference on silicon surface near the melting threshold

To study the material mechanisms of laser-induced silicon microrelief formation the periodic space-modulated heating up to melting point was used. On the basis of measurements of dynamics of surface thermal radiation and of the relief height the conclusion about material mechanisms of relief formation had been made.