It is shown experimentally that a cornea represents a 213 nm UV inhomogeneous material both at depth and around a surface in relation to UV effective absorption coefficient and local laser depth ablation rate, which should be taken into account for a more exact planning of a profile of removed cornea collagen material during eye vision correction.

Описаны оптическая схема, устройство и параметры высокоэффективного световодного преобразователя на вынужденном комбинационном рассеянии (в.к.р.) для импульсных YAG:Nd-лазеров наносекундного диапазона длительностей. Получено преобразование до 90% энергии излучения накачки в стоксовы компоненты. Рассмотрены процессы, ограничивающие эффективность в.к.р.-преобразования в световоде.

The optical scheme, design, and parameters of a high-efficiency fiber converter, which is based on stimulated Raman scattering (SRS), for nanosecond-pulse YAG : Nd lasers are described. The conversion of up to 90% of the pumping-radiation energy into the Stokes components is obtained. The processes that limit the SRS-conversion efficiency in a fiber are considered.

The optical scheme and the design of a high-power YAG:Nd3+ laser, which generates radiation pulses of nanosecond duration at wavelengths of 1064 nm (0.8 J), 532 nm (160 mJ), and 266 nm (40 mJ) with destroyed coherence in a fiber and a smoothed intensity distribution in the beam cross section, are described. The processes that affect the generation efficiency of decoherenized radiation are considered.

Описаны оптическая схема и устройство частотного лазера на YAG : Nd3+ с двухпроходовым усилителем и зеркалом с обращением волнового фронта на вынужденном рассеянии Мандельштама–Бриллюэна в световоде. Максимальная энергия излучения составляет 1000 мДж на длине волны 1.064 мкм и 500 мДж, 200 мДж, 20 мДж на второй, четвертой и пятой гармониках соответственно при расходимости 5 · 10-4 рад и длительности импульса 4.5 нс.

An optical scheme and design of a YAG:Nd 3+ frequency laser with a two-pass amplifier and a mirror with the phase conjugation by the stimulated Brillouin scattering in an optical fiber is described. The maximal radiation energy is 1000 mJ at a 1.064-μm fundamental wavelength and 500, 200, and 20 mJ at the second, fourth, and fifth harmonics, respectively, when the divergence is ∼5 × 10 −4 rad and the pulse duration is 4.5 ns.

We have studied stimulated Raman (SRS) conversion to the first Stokes component of multimode (M 2 = 8) radiation from a YAG:Nd laser with lasing wavelengths of 1.319 µm, 1.338 µm, and 1.357 µm in a barium nitrate crystal. We have obtained pulses of converted radiation with energies up to 120 mJ. We have achieved conversion efficiencies greater than 40% for each of the three Raman laser wavelengths of 1.530 µm, 1.556 µm, and 1.582 µm with divergence of the beams of converted radiation close to the diffraction-limited value (M 2 < 1.5).

Results of studies aimed at the development and optimization of the parameters of a high-power repetitive-pulse Nd3+ :YAG laser, which operates in a free-running mode on spectral lines within a range of 1.32-1.36 mu m, are described. The energy of laser radiation in this range may reach 80% of the radiation energy at 1.064 mu m The major factors that affect the lasing efficiency at a wavelength of 1.32 mu m are the lasing at 1.064 mu m on internal modes of active elements, high-power amplified luminescence at 1.064 mu m forming in the transverse direction inside the quantron (laser head) reflector, and single- and double-pass laser oscillation at 1.064 mu m developing in the laser cavity. High-power repetitive-pulse lasers with the following parameters were created: 1.32 mu m, with a pulse energy of 1.3 J and a pulse repetition rate of 1-50 Hz; 1.32 mu m, 4 J, and 1-10 Hz; and a laser operating at 1.318, 1.338, and 1.357 mu m with energies of 2.1, 1.7, and 1.3 J, respectively, at pulse repetition rates of 1-5 Hz.

The construction peculiarities and output parameters of two YAG:Nd lasers of high quality output radiation using a two-pass amplifier with a phase conjugated mirror are discussed. The first one has the following parameters in each of two channels: pulse energy at 1064 nm - 1900 mJ, at 532 nm - 700 mJ, at 355 nm - 250 mJ, at 266 nm - 130 mJ; beam divergence 0.3 mrad; line width 0.01 cm-1; pulse duration 8 ns; repetition rate 1-5 Hz. The output parameters of the second one whose construction is based on the single flash lamp surrounded by four laser rods (one of the master oscillator, three others of the amplifier) are; pulse energy at 1064 nm - 350 mJ, at 532 nm - 130 mJ, at 266 nm - 25 mJ; energy stability at 1064 nm - 1.5%, at 532 nm - 4.5%, at 266 nm - 9.0%; repetition rate 1.15 Hz.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The results of laser annealing of bulk high-temperature superconductors YBa2Cu3O7−x and Bi2Sr2Ca2Cu3Oy are reported. It is shown that nanosecond pulsed laser treatment of superconductors without further high-temperature processing leads to increasing of critical current density of surface layers of the samples up to 3–4 order within certain interval of laser energy densities due to melting and following crystallization of thin surface layers without degradation of superconducting phase.

It is demonstrated that nanosecond laser processing of superconductive yttrium ceramic by pulses with energy density of 1.7–2.1 J/cm2 permits an increase in critical current density in surface layers by three orders of magnitude.

P-Si layers on c-Si substrate with a thermo-insulating coating (TIC) were irradiated by the 50-ns second harmonic of an Nd-glass laser. Time-resolved measurements, optical microscopy (OM) and scanning electron microscopy (SEM) data for samples with a 0.1–0.9 μm p-Si layer and a 0.1 μm SiO2 or 0.16 μm Si3N4 TIC layer show that if the p-Si layers melt throughout the depth the solidification starts from the surface as well as from the rear. The latent heat released upon coarse grain growth from the rear prevents further crystallization near the top surface and results in partial or complete remelting of the solid phase on the surface.