Enhanced efficiency ultraviolet LiYXLu1 - XF4:RE3+ (RE = Ce,Yb) laser

© 2014 Astro Ltd. We report the results of laser tests in LiYXLu1 - XF4:RE3+ (RE = Ce, Yb; x = 0, 0.3) crystals and the effect on laser characteristics (slope efficiency and tuning range) of such variations of the lasing conditions as the pumping repetition rate, temperature and additional illumination of the active element. It was established that slope efficiency increases and the tuning range of ultraviolet lasing widens and becomes continuous when the crystal is cooled down below 0 °C, or exposed to 532 nm radiation. 266 and 340 nm illumination reduces or completely quenches laser oscillation. The photodynamic processes underlying these effects, such as excited-state absorption and formation/destruction of color centers, are discussed

Why do we learn English language?

This work “Why do we learn English language?” introduces that language is the means of communication; it enables people to understand each other. All the people say: «Undoubtedly, English is number one that every person should learn». So, why do we learn English? Particular attention is focused on learning English for students, to motivate them. The characteristic features of necessity of English are highlighted and described in the research. The relevance of this article is English widespread now in all spheres of our life. English is provided the most significant language even in the small towns. The results of the study that English is popular in the whole world, in all spheres of our life

Two-step photoconductivity in LiY<inf>x</inf>Lu<inf>1 – x</inf>F<inf>4</inf>:Ce,Yb crystals

© 2016, Pleiades Publishing, Ltd.Photoconductivity of LiYxLu1–xF4:Ce,Yb (x = 0–1) crystals is measured under one- and two-step excitation. It is established that the photoconductivity is due to intra-center transitions from excited states of Ce3+ ions. The position of the ground 4 f-state of Ce3+ ion relative to the bottom of the conduction band is determined. The choice of pumping conditions to obtain the lasing on the 5d–4f transitions of trivalent cerium in these active media is substantiated

Investigation of gain characteristics in mixed crystals LiMeF4 (Me = Y, Lu, Yb) doped by Ce3+ ions

Differential gain spectra in the range 295-335 nm were measured in crystals of scheelite structure LiY1 - x Lu x F4 (x = 0-1), doped by Ce3+ ions. It is shown that variation of Lu 3+ and Y3+ ions relative content in LiY1 - x Lu x F4 crystals allows to manipulate the spectral width of the amplification band. Cross-sections of excited-state absorption at the wavelengths of Ce3+ luminescence, probability ratios of formation and thermal destruction of color centers depending on the Y3+ ions content in LiY1 - x Lu x F4 crystals were estimated. Even better gain characteristics have been demonstrated by LiLuF 4:Ce3+, doped by Yb3+ ions. The highest optical gain coefficient with a wide amplification band among studied samples was observed in LiLuF4:Ce3+ crystal, codoped by Yb 3+ ions. © 2014 Pleiades Publishing, Ltd

Photon echo in the ensemble of semiconductor quantum dots spread on a glass substrate

Simple procedure to prepare samples containing semiconductor quantum dots was developed. Test photon echo measurements in the ensemble of quantum dots spread on a glass substrate were performed to study optical dephasing processes

New all-solid-state tunable UV Ce3+, Yb3+:LiY0.4Lu0.6F4 laser

Here we report laser test results of the new UV solid-state active medium based on a Ce3+, Yb3+:LiY0.4Lu0.6F4 mixed crystal pumped by radiation from Ce:LiCAF laser. The 10-Hz pulse repetition rate Ce3+, Yb3+:LiY0.4Lu0.6F4 laser yielded a maximum output power of 0.25 mJ at 311nm in non-optimized non-selective resonator with a maximal slope efficiency of 13%. Tunability from 304 to 332 nm was achieved in the selective single-prism resonator. © 2012 Pleiades Publishing, Ltd

Photodynamic processes and laser performance of Ce, Yb: LiYXLu1-XF4 mixed crystals

Photodynamic processes and temperature dependencies of lasing in Ce+Yb:LYLF mixed crystals are investigated. The mechanisms leading to the observed phenomena and allowing control on the optical qualities of the active media are discussed. © OSA 2013

Laser performance investigation of a new UV active media LiY 0,3Lu0,7F4:Ce3+ and LiY 0,3Lu0,7F4:Ce3++Yb3+

We show that the LiY0,3Lu0,7F4:Ce 3+ and LiY0,3Lu0,7F4:Ce 3++Yb3+ crystals are promising active media of UV spectral range with low-threshold lasing (30-90 mJ/cm2). Due to crystal-chemical approach (additional doping by ions Yb3+) we obtained the effect of suppression of spurious photodynamic processes. The active medium LiY0,3Lu0,7F4: Ce3++ Yb3+ combines properties of saturable amplifier and oscillator with small saturation energy, and promising to generate pulses of ultrashort duration in the UV spectrum. © Published under licence by IOP Publishing Ltd

Spectral-kinetic studies of SrAlF 5 doped by trivalent rare-earth ions

Photochemical properties of Ce 3:SrAlF 5 and Ce 3,Yb 3:SrAlF 5 single crystals together with spectroscopic and kinetic characteristics of several optically nonequivalent impurity centers and energy transfer between them are described. It is shown that co-activation by Yb 3 ions effectively suppresses color centers in Ce,Yb:SAF crystals. It was found out that in Ce,Yb:SAF crystals Yb ions exist simultaneously in 2 and 3 valent state. Three types of optically nonequivalent luminescent centers corresponding to the doublets in luminescence spectrum centered at 290, 305 and 370 nm (Ce I, Ce II, Ce III, respectively) have been observed. Analysis of luminescence spectra and decays leads to the conclusion that there is no energy transfer between either cerium centers or from Ce 3 to Yb 2 apart from the Ce III center which luminescence is slightly quenched by Yb 2. © 2012 Elsevier B.V. All rights reserved