Photoproduction of Long-Lived Holes and Electronic Processes in Intrinsic Electric Fields Seen through Photoinduced Absorption and Dichroism in Ca_3Ga_{2-x}Mn_xGe_3O_{12} Garnets

Long-lived photoinduced absorption and dichroism in the Ca_3Ga_{2-x}Mn_xGe_3O_{12} garnets with x < 0.06 were examined versus temperature and pumping intensity. Unusual features of the kinetics of photoinduced phenomena are indicative of the underlying electronic processes. The comparison with the case of Ca_3Mn_2Ge_3O_{12}, explored earlier by the authors, permits one to finally establish the main common mechanisms of photoinduced absorption and dichroism caused by random electric fields of photoproduced charges (hole polarons). The rate of their diffusion and relaxation through recombination is strongly influenced by the same fields, whose large statistical straggling is responsible for a broad continuous set of relaxation components (observed in the relaxation time range from 1 to about 1000 min). For Ca_3Ga_{2-x}Mn_xGe_3O_{12}, the time and temperature dependences of photoinduced absorption and dichroism bear a strong imprint of structure imperfection increasing with x.Comment: 20 pages, 10 figure

Кристаллы Er,Yb:Ca3RE2(BO3)4 (RE=Y, Gd) – новые среды для лазеров, излучающих в спектральном диапазоне 1,5 мкм

The search for new crystalline host materials for the usage in lasers emitting in the eye-safe spectral range of 1.5–1.6 µm is an important task. The aim of this work was to study the growth technique, spectroscopic properties and laser characteristics of new active media – crystals Er3+,Yb3+:Ca2RE2(BO3)4 (RE=Y, Gd).Calcium-yttrium Er3+,Yb3+:Ca3Y2 (BO3)4 (CYB) and calcium-gadolinium Er3+,Yb3+: Ca2 Gd 2(BO3)4  (CGB) oxoborate crystals co-doped with erbium and ytterbium ions were investigated. Polarized absorption and emission cross-section spectra were determined. The lifetimes of 4I11/2 and 4I13/2 energy levels of Er3+ ions were measured and ytterbium-erbium energy transfer efficiencies were estimated. The calculation of the gain cross-section spectra was performed. By using of Er3+,Yb3+: Ca2 RE 2(BO3)4  (RE=Y, Gd) crystals the laser performance was realized, for the first time to the best of our knowledge. The laser characteristics were studied in a quasi-CW (QCW) laser operation.The wide band with a peak at the wavelength of 976 nm is observed in the absorption spectra of both crystals. This peak coincides with the emission wavelength of the pump laser diodes for Yb-doped active media. The maximum value of absorption cross-section was 1.7 × 10–20 cm2 for polarization E // b for both crystals. The lifetimes of the upper laser level 4I13/2 of Er3+ ions were 580 ± 30 μs and 550 ± 30 μs for Er,Yb:CYB and Er,Yb:CGB crystals, respectively. The energy transfer efficiencies from ytterbium to erbium ions for an Er,Yb:CYB and Er,Yb:CGB crystals were 94 % and 96 %, respectively. According to gain spectrum of the Er,Yb:CYB crystal the gain band peak is centered at the wavelength of 1530 nm. The maximum QCW output power was 0.5 W with slope efficiency of 13 % regarding to absorbed pump power for an Er,Yb: CYB crystal. The laser beam parameter M2 did not exceed &lt; 1.5.Based on the obtained results, it can be concluded that these crystals are promising active media for lasers emitting in the spectral range of 1.5–1.6 μm for the usage in laser rangefinder and laser-induced breakdown spectroscopy systems, and LIDARs.Поиск новых кристаллических матриц для применения в лазерах, излучающих в условно безопасном для глаз спектральном диапазоне 1,5–1,6 мкм, является актуальной задачей. Целью данной работы являлось изучение технологии роста, спектроскопических свойств и генерационных характеристик новых активных сред – кристаллов Er3+,Yb3+:Ca2RE2(BO3)4  (RE=Y, Gd).В качестве исследуемых образцов использовались кристаллы кальций-иттриевого Er3+,Yb3+:Ca3Y2(BO3)4 (CYB) и кальций-гадолиниевого Er3+,Yb3+: Ca2 Gd 2(BO3)4  (CGB) оксоборатов, соактивированных ионами эрбия и иттербия. В результате определены спектры поперечных сечений поглощения и стимулированного испускания в поляризованном свете. Определены времена жизни энергетических уровней 4I11/2 и 4I13/2 иона эрбия, а также проведена оценка эффективности переноса энергии от ионов иттебрия к ионам эрбия. Выполнен расчет спектров поперечных сечений усиления. Впервые с использованием кристаллов реализована лазерная генерация, изучены генерационные характеристики в квазинепрерывном режиме генерации.В спектрах поглощения для обоих кристаллов наблюдается полоса с пиком на длине волны 976 нм, что согласуется с длиной волны испускания лазерных диодов, применяемых для накачки активных элементов с ионами Yb3+ . Наибольшее значение поперечного сечения поглощения для обоих кристаллов составило 1,7×10–20 см2 для поляризации E // b на длине волны 976 нм. Время жизни верхнего лазерного уровня 4I13/2 составило 580 ± 30 мкс и 550 ± 30 мкс для кристаллов Er,Yb:CYB и Er,Yb:CGB соответственно. Эффективность переноса энергии от ионов иттербия к ионам эрбия составила 94 % для кристалла Er,Yb:CYB и 96 % для Er,Yb:CGB. Расчет спектра усиления для кристалла Er,Yb:CYB, показал что максимум полосы усиления находится на длине волны 1530 нм. Максимальное значение выходной мощности в квазинепрерывном режиме генерации составило 0,5 Вт при дифференциальной эффективности по поглощенной мощности накачки 13 % для кристалла Er,Yb:CYB, параметр распространения лазерного пучка М2 не превышал 1,5.На основе полученных результатов, можно сделать вывод, что данные кристаллы являются перспективными активными средами для лазеров, излучающих в спектральном диапазоне 1,5–1,6 мкм, для применения в составе систем лазерной дальнометрии, лазерно-искровой эмиссионной спектрометрии и лидаров

ПРИМЕНЕНИЕ МЕТОДОВ ФЮХТБАУЭРА–ЛАДЕНБУРГА И СООТВЕТСТВИЯ ДЛЯ ОПРЕДЕЛЕНИЯ СПЕКТРОВ СЕЧЕНИЙ СТИМУЛИРОВАННОГО ИСПУСКАНИЯ НЕОДИМОВЫХ ЛАЗЕРНЫХ СРЕД

Rare-earth doped crystals with broad bands of gain spectra are attractive for femtosecond laser applications. Therefore, for this purposes crystals with disordered structure are of great interest. In this article we investigate laser-related spectroscopic properties of new trigonal crystals Nd3+:Ca10K(VO4 )7 (Nd:CKV), Nd3+:Ca9 La(VO4 )7 (Nd:CLaV) и Nd3+:Ca10Li(VO4 )7 (Nd:CLiV). The Füchtbauer-Ladenburg equation and the integral reciprocity method were applied for determination of stimulated emission cross section spectra for Nd3+ ions. The maximum values of emission cross sections and bandwidth (FWHM) near λ = 1,07 μm are 9,33·10 -20cm2 (σ – polarization, Nd:CKV) and 30 nm (π – polarization, Nd:CKV), near λ = 1,35 μm – 1,55·1020cm2 and 50 nm (π – polarization, Nd:CKV). The broad and smooth bands of the gain spectra in the regions near 1,07 and 1,35 μm make it possible to generate ultra short light pulses with duration of about 60 fs (1,07 µm) and 45 fs (1,35  µm) in the mode-locking regime. Для создания лазеров, генерирующих импульсы ультракороткой длительности, представляют большой интерес лазерные материалы с широкими полосами усиления. В этой связи значительный интерес представляют структурно разупорядоченные материалы, в частности новые кристаллические среды, принадлежащие тригональной сингонии Nd3+:Ca10K(VO4 )7 (Nd:CKV), Nd3+:Ca9 La(VO4 )7 (Nd:CLaV) и Nd3+:Ca10Li(VO4 )7 (Nd:CLiV). В данной работе формула Фюхтбауэра-Ладенбурга и интегральный метод соответствия применены для определения спектров сечений стимулированного испускания указанных выше кристаллов на переходах 4 F3/2 → 4 I9/2, 4 F3/2 → 4 I11/2, и 4 F3/2 → 4 I13/2 иона неодима. Максимальные пиковые значения сечений стимулированного испускания и наибольшие спектральные ширины полос в области 1,07 мкм составляют 9,33·10-20 см2 (σ-поляризация, Nd:CKV) и 30 нм (π-поляризация,  Nd:CKV), в области 1,35 мкм – 1,55·10-20 см2 и 50 нм (π-поляризация, Nd:CKV). Полосы стимулированного испускания, а следовательно, и усиления в областях спектра 1,07 и 1,35 мкм являются гладкими и бесструктурными с ширинами, позволяющими получать ультракороткие импульсы света с длительностью  ≈  60 фс (1,07 мкм), ≈ 45 фс (1,35 мкм) в лазерах на исследованных лазерных средах, работающих в режиме синхронизации мод.

The ethics of digital well-being: a multidisciplinary perspective

This chapter serves as an introduction to the edited collection of the same name, which includes chapters that explore digital well-being from a range of disciplinary perspectives, including philosophy, psychology, economics, health care, and education. The purpose of this introductory chapter is to provide a short primer on the different disciplinary approaches to the study of well-being. To supplement this primer, we also invited key experts from several disciplines—philosophy, psychology, public policy, and health care—to share their thoughts on what they believe are the most important open questions and ethical issues for the multi-disciplinary study of digital well-being. We also introduce and discuss several themes that we believe will be fundamental to the ongoing study of digital well-being: digital gratitude, automated interventions, and sustainable co-well-being

Development of Growth Technologies for the Photonic Single Crystals by the Czochralski Method at Institute for Single Crystals, NAS of Ukraine

The present paper briefly overviews the application of the Czochralski method for growth of a set of oxide crystals for photonics, as well as the design of equipment at the Institute for Single Crystals, NAS of Ukraine. The examples of crystal growth and their characterization are described. The simultaneous Q-switched lasing and self-Raman frequency conversion were demonstrated in Nd-doped $PbWO_4$ and $PbMoO_4$ crystals grown by the Czochralski method. The slope lasing efficiency obtained for a $PbMoO_4:Nd^{3+}$ laser is the best result for all the crystals with the scheelite-type structure. A detection unit with high scintillation characteristics based on a large volume (V ≈ 350 cm^3) $CdWO_4$ crystal was produced. Crystal growth procedures and properties of new double tungstate and vanadate crystals are presented, too

Er,Yb:Ca3RE2(BO3)4 (RE=Y, Gd) – Novel 1.5 μm Laser Crystals

The search for new crystalline host materials for the usage in lasers emitting in the eye-safe spectral range of 1.5–1.6 µm is an important task. The aim of this work was to study the growth technique, spectroscopic properties and laser characteristics of new active media – crystals Er3+,Yb3+:Ca2RE2(BO3)4 (RE=Y, Gd).Calcium-yttrium Er3+,Yb3+:Ca3Y2 (BO3)4 (CYB) and calcium-gadolinium Er3+,Yb3+: Ca2 Gd 2(BO3)4  (CGB) oxoborate crystals co-doped with erbium and ytterbium ions were investigated. Polarized absorption and emission cross-section spectra were determined. The lifetimes of 4I11/2 and 4I13/2 energy levels of Er3+ ions were measured and ytterbium-erbium energy transfer efficiencies were estimated. The calculation of the gain cross-section spectra was performed. By using of Er3+,Yb3+: Ca2 RE 2(BO3)4  (RE=Y, Gd) crystals the laser performance was realized, for the first time to the best of our knowledge. The laser characteristics were studied in a quasi-CW (QCW) laser operation.The wide band with a peak at the wavelength of 976 nm is observed in the absorption spectra of both crystals. This peak coincides with the emission wavelength of the pump laser diodes for Yb-doped active media. The maximum value of absorption cross-section was 1.7 × 10–20 cm2 for polarization E // b for both crystals. The lifetimes of the upper laser level 4I13/2 of Er3+ ions were 580 ± 30 μs and 550 ± 30 μs for Er,Yb:CYB and Er,Yb:CGB crystals, respectively. The energy transfer efficiencies from ytterbium to erbium ions for an Er,Yb:CYB and Er,Yb:CGB crystals were 94 % and 96 %, respectively. According to gain spectrum of the Er,Yb:CYB crystal the gain band peak is centered at the wavelength of 1530 nm. The maximum QCW output power was 0.5 W with slope efficiency of 13 % regarding to absorbed pump power for an Er,Yb: CYB crystal. The laser beam parameter M2 did not exceed &lt; 1.5.Based on the obtained results, it can be concluded that these crystals are promising active media for lasers emitting in the spectral range of 1.5–1.6 μm for the usage in laser rangefinder and laser-induced breakdown spectroscopy systems, and LIDARs

Luminescence of PbWO4O_{4} single crystals doped with fluorine

Tumour necrosis factor (TNF)-alpha-converting enzyme (TACE) is a metalloproteinase-disintegrin that releases soluble TNF-alpha from cells by cleaving within the extracellular domain of membrane-bound pro-TNF-alpha. It was proposed that TNF-alpha is involved in the pathogenesis of psoriasis, and it is therefore suggested that TACE has important roles in psoriasis. However, it is unclear whether TACE is expressed in psoriatic tissue.To clarify whether TACE is expressed in psoriatic lesions and whether expression levels of TACE mRNA are increased in lesional compared with nonlesional psoriatic skin.Skin biopsies were obtained from patients with psoriasis. We examined the expression of TACE in psoriatic tissues using a novel real-time quantitative reverse transcriptase-polymerase chain reaction method and immunohistochemical analysis.There was a significant rise in the level of TACE mRNA expression in lesional psoriatic skin compared with nonlesional skin in all patients. There was a statistically significant rise in the level of TACE mRNA expression in lesional psoriatic skin compared with nonlesional skin (mean +/- SD TACE/glyceraldehyde-3-phosphate dehydrogenase ratio 0.031 +/- 0.012 vs. 0.009 +/- 0.002, P < 0.05). In lesional psoriatic skin, immunostaining with anti-TACE antibody was present throughout all layers of the epidermis. TACE immunostaining was found in the cytoplasm of keratinocytes. There was staining associated with blood vessels in the papillary dermis and perivascular inflammatory cells. In particular, mast cells showed strong staining. They contained numerous granules that were stained for TACE in the cytoplasm.The findings of the present study suggest that elevation of TACE mRNA in psoriatic lesions is due to many cells, particularly mast cells, that function in lesional psoriatic skin as an important source of TNF-alpha and other cytokines