E. B. Yakovlev

Peculiarities of the formation of planar micro-optic elements on porous glass substrates under the effect of laser radiation followed by sintering

The theoretical and practical approaches to the formation of micro-optic elements (MOE) for the integrated optical communication on substrates made of different materials, including silicate glasses, have been reviewed. The applicability of high-silica porous glasses (PG) fabricated by a homogeneous acid leaching of two-phase alkali borosilicate glasses as basic matrices for laser formation of MOE of different types (microlenses and microchannels) has been discussed. It has been demonstrated that sintering laser-modified PGs at temperatures ensuring the collapse of the pore can be used to stabilize MOE optical properties. The results of choosing the time-temperature mode for sintering PG substrates with a planar MOE-strip waveguide (SW) providing the SW fixation on a completely sintered substrate were presented.

Modeling of thin Cr film oxidation under the action of ultrashort laser pulses

The paper is devoted to modeling of thin metallic film on a glass substrate oxidation under the action of ultrashort laser pulse sequence with taking into account surface and bulk oxidation and electronic excitation.

Surface Sintering of Porous Glass Plates under Laser Radiation

The kinetics of surface sintering of flat plates of the 96SiO2 · 3.8B2O3 · 0.2Na2O (mol %) porous glass exposed to CO2 laser radiation is investigated under conditions when either the irradiation time is varied at a constant radiation power density or the radiation power density is varied at a constant irradiation time. It is established that the irradiation time is the most appropriate controlled parameter in the process of sintering. A decrease in the thickness of the porous layer sintered on the plate surface is accompanied by an increase in the radii of curvature of the interfaces of this layer.

Local laser-induced change of optical properties in the bulk of photochromic porous silicate glass doped by silver and copper halides

The principles of the formation of modified areas of a spherical shape and complex structure in porous glass plates doped by silver and copper halides under the continuous radiation of a fiber laser focused inside the plate have been formulated. The results of the study of the obtained modified areas are given.

Simulation of the absorption of a femtosecond laser pulse in crystalline silicon

The effect of the nonlinearity of the absorptivity and absorption coefficient on the process of the intense photoexcitation of silicon is studied on the basis of a model of the two-photon excitation of a semiconductor with consideration for external emission. Correlation between the results of simulation of the absorption of a femtosecond laser pulse in single-crystal silicon and experimental data under conditions of the femtosecond excitation of surface plasmon polaritons makes it possible to refine the mechanism of changes in the absorptivity and to make an inference regarding the necessity of considering these changes when assessing the conditions of the laser treatment of semiconductors. Avenues for further improvement of the theoretical model are discussed.

Laser induced structural changes in porous glass due to hot and cold compaction

A comparison is presented of the structural changes occurring in porous glass during laser-induced hot and cold compaction. The changes occurring in modified regions of different compaction processes when a porous-glass plate with a micro-region is sintered in a furnace are also compared.

Laser-induced local change in optical properties of alkaline-borosilicate glasses

The process of the formation of microregions (MRs) in the volume of alkaline-borosilicate glasses using the method which includes the production of porous glass (PG) by leaching two-phase alkaline-borosilicate glass in acid and the action on PG of laser radiation of a wavelength practically not absorbed by glass has been studied. The optical properties of MRs and the possibility of their preservation after PG sintering in a furnace to obtain a quartzoid glass are studied.

The effect of electron emission on the heating of metals by femtosecond laser pulses

The interaction of femtosecond laser pulses with metals is discussed, taking into account electron emission, photoemission, and thermal emission, which causes Coulomb explosion because of the accumulation of excess positive charge on the surface of the target and the generation of an electric field. It is established that emission has a weak effect on the thermophysical and optical properties of solids, and therefore it can be neglected when analyzing the heating of metals by femtosecond laser pulses.

Dynamics of the permittivity of a semiconductor acted on by a femtosecond laser

A theoretical analysis of how the permittivity of a broad-band semiconductor varies while it is being acted on by a femtosecond laser pulse is presented, taking into account various types of emission phenomena. The spatial permittivity distribution considered here is modelled experimentally, using surface plasmon resonance on the corresponding multilayer structures and is compared with the data of femtosecond microstructuring of silicon at a wavelength of 1.25 µm.

Laser-induced passivation of porous glass to protect it from chemical degradation and aging

A technique for forming thermally densified layers on opposite wafer surfaces so as to retain a complex well-developed structure of porous glass wafers is proposed. These thermally densified layers passivate and protect porous glass from chemical degradation and aging. The process involves the formation of thermally densified layers and removal of graphite particles from these layers. The formation of a thermally densified layer on the surface of a porous glass wafer was induced by an ytterbium fiber laser with wavelength λ = 1.06 μm, pulse duration τ = 100 ns, and pulse repetition frequency ν = 30–50 kHz. Graphite particles were removed from the surface of porous glass wafers on the same laser setup model. Even 10 months after the thermally densified layers had been formed, loss in transmittance in the entire wavelength range was less than 5–7%. The results of examining the surface relief of porous glass wafers before and after a thermally densified layer had been formed on a scanning probe microscope with an arbitrary selection of 500 × 500-nm scanning areas are presented.