Історія розвитку принципу збереження теплоти

(uk) У статті розкрито етапи формування поняття принципу збереження теплоти.(en) The stages of forming of concepttion of principle of maintainanceof warmth are exposed in the article

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

Observation of triply coincident nonlinearities in periodically poled KTiOPO4

We report the simultaneous quasi-phase-matching of all three possible nonlinearities for propagation along the X axis of periodocally poled (PP) KTiOPO4 (KTP) for second-harmonic generation of 745 nm pulsed light from 1490nm subpicosecond pulses in a PPKTP crystal with a 45.65 micrometer poling period. This confirms the recent Sellmeier fits of KTP by K. Kato and E. Takaoka [Appl. Opt. 41, 5040 (2002)]. Such coincident nonlinearities are of importance for realizing compact sources of multipartite continuous-variable entanglement [Pfister et al., Phys. Rev. A 70, 020302 (2004)] and we propose a new simpler method for entangling four fields, based on this triple coincidence.Comment: 3 pages, 4 figures, submitted for publicatio

Narrowband, tunable, 2 µm optical parametric master-oscillator power amplifier with large-aperture periodically poled Rb:KTP

n/

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

n/

Multistep Parametric Processes in Nonlinear Optics

We present a comprehensive overview of different types of parametric interactions in nonlinear optics which are associated with simultaneous phase-matching of several optical processes in quadratic nonlinear media, the so-called multistep parametric interactions. We discuss a number of possibilities of double and multiple phase-matching in engineered structures with the sign-varying second-order nonlinear susceptibility, including (i) uniform and non-uniform quasi-phase-matched (QPM) periodic optical superlattices, (ii) phase-reversed and periodically chirped QPM structures, and (iii) uniform QPM structures in non-collinear geometry, including recently fabricated two-dimensional nonlinear quadratic photonic crystals. We also summarize the most important experimental results on the multi-frequency generation due to multistep parametric processes, and overview the physics and basic properties of multi-color optical parametric solitons generated by these parametric interactions.Comment: To be published in Progress in Optic