S. V. Makarov

Sub- and near-threshold femtosecond laser nanostructuring of solid surfaces

Two femtosecond laser nanograting fabrication mechanisms, including new ones recently found in our laboratory and related to sub-and near-threshold surface nanostructuring, are illustrated using experimental data for diverse solids nanostructured by 744-nm femtosecond laser pulses.

Evolution of black silicon nano- and micro-scale surface topologies upon femtosecond laser irradiation

Gradual evolution of silicon surface topology from one-dimensional to two-dimensional nanogratings and then to isotropic sets of nanospikes was observed by increasing IR and UV femtosecond laser irradiation dose (the variable number of incident laser pulses at the constant laser fluence). The fundamental mechanisms of these topological transformations are discussed.

Numerical simulation of high pressure HeCd plasma generated by E-beam or by electrical discharges

Summary form only given. A model of an atmospheric pressure HeCd laser pumped by a pulsed electron beam has been developed which makes it possible to calculate temporal and energy characteristics of the laser radiation. Processes restricting the specific pumping energy have been analyzed under optimal conditions of medium excitation. It is shown that the repetitive-pulse operation with a small duty ratio can be realized in the HeCd laser. Time and energy characteristics have been studied numerically of the radiation from a high pressure HeCd laser excited by a microsecond electron beam at wavelengths of 441.6 and 537.3 nm which depends on the pump duration, namely, the efficiency rises as the pump duration is reduced. A method is suggested for enhancement of the laser power at long pump pulses, which consists of increasing the temperature of the HeCd plasma electrons with the use of an external electric field. The optimal field strength has been determined. It is shown that the emitted radiation power can be modulated by means of pulsed switching of the electric field. The shape of the secondary electron degradation spectrum has weak influence on pumping rates of upper laser levels by direct electron impact, therefore lasings are identical in the case of equality of energy depositions.

Modeling of a high-pressure helium–cadmium laser excited by electron beam pulses

A model is proposed of an atmospheric-pressure He–Cd laser pumped by electron beam pulses. This model can be used to calculate the time and energy characteristics of laser radiation. An analysis is made of the processes limiting the specific pump energy under optimal excitation conditions. The results demonstrate feasibility of operation of a pulse-periodic He–Cd laser with a small off-duty factor.