Yu. S. Protasov

Study of opto-mechanical characteristics of interaction of ultrashort laser pulses with polymer materials

The opto-mechanical characteristics, such as the specific mechanical recoil momentum, the specific impulse, and the energy efficiency, of the laser ablation of flat polymer targets ((C2F4)n, (CH2O)n) have been determined experimentally for the first time for the case of excitation with femtosecond pulses (τ ∼ 45–70 fs) of UV-IR (λ ∼ 266, 400, 800 nm) laser radiation (I0 up to 1015 W/cm2) under normal atmospheric and vacuum (p ∼ 10−4 mbar) conditions. The efficiency of mechanical recoil momentum generation is analyzed for various regimes of the laser irradiation.

Gas-plasma flows under femtosecond laser ablation for metals in vacuum

New information on particle distribution over velocities, the mean-mass velocity, and the degree of monochromaticity of gas-plasma flow under femtosecond (τ ∼ 45 fs, λ ∼ 800 nm) laser ablation is obtained for several metals (Ti, Zr, Mo, Nb, Cu) in vacuum (p ∼ 5 × 10−2 Pa) by means of combined interferometry.

Efficiency of the conversion of radiation energy into kinetic energy of a gas-plasma flow during femtosecond laser ablation of metals in vacuum

Using the methods of combined interferometry, we obtained new data on the momentum coupling coefficient and conversion efficiency of radiation energy into kinetic energy of a gas-plasma stream during femtosecond laser ablation (τ ∼ 45 fs, λ ∼ 800 nm) of several metals (Ti, Zr, Mo, Cu) in vacuum (p ∼ 5 × 10−2 Pa).

Experimental investigation of the dynamics of laser-induced gas-plasma flows under femtosecond laser ablation of copper in vacuum

Thermophysical and gas-dynamic characteristics of gas-plasma flows induced by ultrashort laser pulses interacting with a thin-film copper target in vacuum were studied experimentally. Using combined laser interferometry and complex processing of experimental data, we estimated the momentum coupling coefficient and the efficiency of laser-energy conversion to kinetic energy, spatiotemporal distributions of the number density and velocities of particles, pressure, and temperature in the gas-plasma flow. We provide comparative analysis of presented data with those found in the literature, which were obtained by other methods.

Experimental investigation of recoil-momentum-generation efficiency under near-IR femtosecond laser ablation of refractory metals in vacuum

The use of ultrashort laser pulses is a way to increase recoil momentum under laser ablation of materials, because, in this case, the energy deposition per unit volume of the target material is substantially higher due to reduced heat dissipation. By using methods of combined interferometry, we estimated the specific impulse (∼200–900 s), momentum coupling coefficient (∼2 × 10−5−3 × 10−4 Ns/J), laser-energy conversion efficiency to kinetic energy of the gas-plasma flow (∼0.05–0.82), and degree of the gas-plasma flow monochromaticity (∼0.72–0.92) under femtosecond (τ ∼ 45 fs, λ ∼ 800 nm) ablation of refractory metals (Ti, Zr, Mo, and Nb) in vacuum.

A Pulsed Source of Short-Wave UV Radiation of High Power Density

A pulsed–periodic source of high-power (∼1 MW/cm2) short-wave UV radiation with a developed luminous body and a high radiance temperature (∼30 kK) in the UV and near-VUV spectral region is described. The emitting plasma in the source is heated as a result of shock-wave interaction of counter-propagating supersonic dense-plasma streams formed by erosion-type magnetoplasma compressors.

A Light-Erosion Source of High-Enthalpy Gas-Plasma Flows of Complex Chemical Composition

A light-erosion generator of high-enthalpy gas-plasma streams of complex chemical composition has been developed on the basis of a plasma-dynamic broadband lamp-type source of short-wave UV radiation with a high power density of ∼1 MW/cm2 and a luminance temperature of ∼3.5 eV. The results of studies in a vacuum and a gas at a finite pressure show that the generator ensures the finely controlled characteristics of the mass flow rate: the velocity is v~ = 2–10 m/s and the mass consumption ratio is m. ≅ 2–3 mg/J.

Generation of gas-plasma flows by laser ablation of photopolymerizable compositions

The results of studying the effectiveness of using photopolymerizable compositions (PPC) in various-purpose laser-plasma facilities with regard to the transportation and fine dosing of the working medium, as well as providing a long service life and reliability, are presented. The characteristics of the pulsed and continuous laser radiation curing of PPC and mixtures thereof are discussed in terms of the spectral-energetic characteristics of the incident radiation. The thresholds of nanosecond laser ablation in the UV and near-IR regions, specific ejected mass, momentum coupling coefficient, and efficiency of conversion of laser radiation energy into the kinetic energy of the laser-induced gas-plasma ablation jet for PPC in the liquid and solid states. The highest efficiency of generation of the gas-plasma ablation jet was achieved for the laser irradiation of initially liquid PPC at a wavelength of 355 nm, a wavelength optimal for the photopolymerization of PPC.

On the efficiency of laser ablation of photopolymerizing compositions in liquid and solidified states

The efficiency of laser ablation of photocuring compositions that are working substances of various laser-plasma facilities is investigated for the first time. A substantial difference in spectral-energetic laser ablation thresholds, specific mass consumption, momentum coupling coefficient, and conversion efficiency of the laser energy to the kinetic energy of gas-plasma flow for liquid and solidified phases is demonstrated. Application of this class of working media allows not only solving problems related to laser ablation of a target, transport, fine dosing, and obtaining long lifetime and reliability of laser-plasma-based technological setups, but also considerably broadens the range of their operational characteristics.

Brightness-Spectrum Characteristics of the Surface Laser Plasma of Polymeric Targets in the VUV Spectral Region

The brightness-spectrum and energy parameters in the VUV range of the spectrum (hν ∼ 9–70 eV) of the surface laser plasma of polymeric targets in vacuum are determined experimentally. Using the experimental technology of double open and closed ionization chambers (as radiation detectors) requiring no absolute energy calibration in a wide range of regulation parameters of the effect of standard laser frequencies, we obtained new data on multifactor radiative gasdynamic processes of effect which are needed to determine emission and mass-output characteristics of the targets irradiated under vacuum.