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Abstract: The paper presents theoretical approach to simulation of nonlinear optical absorption in zinc selenide crystals doped with cobalt (II) ions (ZnSe:Co2+), which was reported by us earlier (Opt. Laser Technology, V. 35, (2003), 169). We used ZnSe:Co2+ crystals as saturable absorbers for generation of giant-pulse eye-safe laser radiation. It was found that minimal optical losses (maximal final transmission) occurred for ZnSe samples containing 1.6×1019 cm−3 of Co2+ ions. Band structure and photoinduced molecular dynamics simulations were performed to explain the parabolic dependence of optical losses versus Co2+ concentration. The minimum was shown to be the result of photoinduced anharmonic electron–phonon interaction. [Copyright &y& Elsevier]

ZnSe:Co2+ crystals were grown by the Bridgeman technique. Optical absorption measurements showed non-uniform distribution of Co2+ ions along the as-grown crystals. Using Pfann formula the distribution coefficient of Co2+ ions between crystal and melt was estimated to be 0.5. Transmission dependence on laser power at λ=1535 nm was investigated for different Co2+ ions concentration. Maximal final transmission was found for ZnSe samples containing 1.6×1019 cm−3 of Co2+ ions. Obtained ZnSe:Co2+ samples were used as saturable absorbers to generate giant-pulse eye-safe laser radiation. KIGRE QE-7S rod placed in resonator cavity was used as active element. [Copyright &y& Elsevier]

The reflectance profilometer, constructed in Institute of Optoelectronics, Military University of Technology, is an optoelectronic device based on the laser remote sensing technique, designed for use on unmanned aerial vehicles. The main task of the profilometer is to analyze the reflectance signals for laser radiation from the multispectral range: 850, 905, and 1550 nm. On the basis of the analysis the profilometer enables two fundamental functions: to define the shape of the ground and identify elements of terrain coverage, along with analysis of its physicochemical properties. The reflectance profilometer is a system based on a modern concept of measurement, allowing to obtain unique information about tested objects, whose measurements or detection are not possible by means of thermal imaging systems and systems operating in the visible range. The received information is visualized in 3D format, which allows for more accurate, precise and comprehensive way of analyzed area model presentation. [ABSTRACT FROM AUTHOR]

We report methodology of three-dimensional laser beam shaping. The analytical and numerical analysis is presented. A strategy for designing optical system involves the controlled application of aberrations which is realized by specific aspheric lens shaping. The goal is to obtain the desired optical power density distribution in space, which is optimal for selected application. The proposed method is discussed with regard to the design of optical transmitter for laser shooting simulator, however the developed methodology can be used for a number of other light shaping applications. [ABSTRACT FROM AUTHOR]

A generalized model of a passively repetitively Q-switched three-level laser is presented. The method for evaluation of the small-signal gain coefficient and the dissipative losses of a three-level laser is shown. To demonstrate the use of this optimization procedure, it was applied to a microchip laser generating 1.5-μm radiation. The model may be expanded for a four-level laser by replacing the calculation of the small-signal gain coefficient. [ABSTRACT FROM AUTHOR]

Abstract: Thin films of Co,Si:YAG were grown on YAG and Er,Yb:YAG substrates by means of the isothermal liquid-phase epitaxy (LPE) dipping technique. X-ray diffraction analysis, optical transmission spectra measurements, and passive Q-switching experiments were performed to characterize the obtained layers. Absorption saturation measurements of Co,Si:YAG thin films were carried out at 1.54μm. Passive Q-switching of the Er:glass laser by use of epitaxial Co,Si:YAG/YAG was observed. We demonstrated experimentally that the Co,Si:YAG layers could be used as an effective saturable absorber for the lasers operating near 1.5μm. [Copyright &y& Elsevier]

It was shown a possibility to enhance the output laser stimulated second harmonic susceptibility for Pb 5 Ge 3 O 11 single crystals in their ferroelectric phase using an external laser light and appropriate doping by Cr 3+ ions. The improvement of the Nonlinear Optical effect is achieved due to local enhancement of the local charge density non-centrosymmetry (acentricity), changes of the effective excitation of the occupied states and additional photo-polarization of the 3d-localized Cr 3+ states. The addition of Cr 3+ ions leads to additional enhancement of hyperpolarizability. To clarify the origin of the observed effect, and to understand the origin of its interesting properties, the calculations of the band structure of Pb 5 Ge 3 O 11 were performed using, for the first time, the first-principles DFT calculations. These reveal that Pb 5 Ge 3 O 11 has an indirect energy band gap E g equal to about 2.6 eV and that the highest occupied valence band is very flat and is separated from the remaining valence bands by a small energy gap equal to about 0.3–0.4 eV. This discovery could explain many unexplained puzzling experimental results and especially the different photo-activated effects found previously in Pb 5 Ge 3 O 11 . The possible origin of the DFT calculated band structure is discussed. The enhancement of the second order optical susceptibility was explained within a framework of additional charges of the particular dopants during the coherent laser illumination. [ABSTRACT FROM AUTHOR]

Czochralski growth of Ca4GdO(BO3)3 (GdCOB) single crystals, pure and doped with several rare earth ions (Nd3+, Pr3+, Tm3+, and Sm3+), has been carried out. As-grown single crystals free from inclusions, bubbles and cracks were 20 mm in diameter and up to 60 mm in length. Optical absorption spectra of 6 at% thulium and samarium doped calcium gadolinium oxoborate were measured and presented. It was found that introduction of Pr3+ and Tm3+ ions leads to an increase of second-order photoinduced effects in GdCOB. The second harmonic generation shows an increase of at least 35% under the influence of photoinducing nitrogen laser (λ=377 nm) power. [Copyright &y& Elsevier]