Формування дослідницьких умінь учнів старших класів у процесі навчання інформатики

(uk) У статті розглядається формування дослідницьких умінь учнів у навчанні інформатики з використанням роздаткового матеріалу, що дає змогу учню глибоко засвоїти навчальний матеріал.(ru) В статье рассматривается формирование исследовательских умений учеников в обучении информатике с использованием раздаточного материала, который дает возможность им глубоко усвоить учебный материал

Periodically domain−structured KTiOPO4 crystals grown from high temperature solution

International audiencePeriodically-poled ferroelectric crystals proved to be the most promising technique for exploiting at the best nonlinear optical frequency conversion properties of materials using quasi-phase matching (QPM). Until now the common method for obtaining periodically-poled ferroelectric crystals is by electric-field poling. In this technique local inversion of the spontaneous polarization is produced in a single-domain crystal by applying an electric field on a periodic electrode deposited on the crystal surface. The poling technology for nonlinear crystals like KTiOPO4, LiNbO3 and LiTaO3 is by now reliable to produce QPM gratings with periods down to about 8 µm. But the thickness of the periodically poled slabs is restricted to 1 mm for these gratings periods, which limits their use to low- and medium- power applications

Bulk PPKTP by crystal growth from high temperature solution

International audiencePeriodically-poled ferroelectric crystals show unprecedented efficiency and properties otherwise impossible to obtain. Unfortunately, the sample thickness obtainable today limits their use to low and moderate power application. With the aim of increasing the size of periodically domain-structured crystals with a controlled and regular grating period, we proposed an epitaxial growth process using seeds made of thin plates domain engineered by electric field poling. We demonstrated this process with the ferroelectric crystal KTiOPO4 (KTP) which is one of the most promising candidate materials for that purpose. The poling step requires a sample exhibiting (001) and (00 (1) over bar) faces, so that the growth step has to be performed onto these faces. This constraint is a difficulty to circumvent as these faces are not present in the standard equilibrium morphology. It is then necessary to find the growth conditions enabling to work below the roughening temperature of these faces. By using a high temperature solution method, the so-called "flux method", and by choosing an appropriate chemical composition of the flux solution, we obtained periodically domain-structured KTP layers with thicknesses up to 800 mu m and regular periodicity onto (001) and (00 (1) over bar) faces of the initial PPKTP seeds

Template-growth of periodically domain-structured KTiOPO4

International audienceWe performed the first growth, from a high temperature solution, of a 38.86 μm-periodicity PPKTP crystal of good optical quality over a thickness of more than 800 μm onto each of the two faces perpendicular to the c direction of a PPKTP substrate previously obtained by electric field poling. The quasi-phase matched second harmonic generation properties in the grown layer and substrate are similar and in accordance with calculation

Sub-nanosecond, 1-10 kHz, low-threshold, non-critical OPOs based on periodically poled KTP crystal pumped at 1,064 nm

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High average power ultra-short pulse Yb-doped fiber amplifier : experimental realization and accurate theoretical modeling

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Gisela Eckhardt and the Raman laser

Gisela Eckhardt was one of the early pioneers in laser physics, discovering the principle behind the Raman laser in 1962. Valdas Pasiskevicius, Richard Mildren and David Burman tell the largely unknown story of her life - and the challenges she faced as a woman in physics.5 page(s

Thermal limitations of volume Bragg gratings when used in lasers for spectral control

We investigated the effect of absorption in volume Bragg gratings (VBGs) and the associated temperature effects that appear when they are used as mirrors in diode pumped solid-state lasers. The primary result is an uneven longitudinal temperature distribution that causes a reduction in the reflectivity and the spectral selectivity.Qc 2012011