Optical vector network analysis of ultra-narrow transitions in 166^{166}Er3+^{3+}:7^7LiYF4_4

We present optical vector network analysis (OVNA) of an isotopically purified $^{166}$Er$^{3+}$:$^7$LiYF$_4$ crystal. The OVNA method is based on generation and detection of modulated optical sideband by using a radio-frequency vector network analyzer. This technique is widely used in the field of microwave photonics for the characterization of optical responses of optical devices such as filters and high-Q resonators. However, dense solid-state atomic ensembles induce a large phase shift on one of the optical sidebands which results in the appearance of extra features on the measured transmission response. We present a simple theoretical model which accurately describes the observed spectra and helps to reconstruct the absorption profile of a solid-state atomic ensemble as well as corresponding change of the refractive index in the vicinity of atomic resonances.Comment: 4 pages, 5 figure

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

Methodological problems of sociological conceptualization of the notion of media audience

В статье рассматривается специфика социологического подхода к исследованию аудитории средств массовой информации. Особое внимание уделяется проблемам теоретико-методологического анализа понятий «аудитория» и «аудитория СМИ», их общим и специфическим признакам. Даётся типология аудиторий СМИ и характеризуются факторы их формирования.The article deals with the specifics of the sociological approach to the study of the media's audience. Particular attention is given to theoretical and methodological analysis of the concepts of «audience» and «media audience», their general and specific characteristics. Given typology media audiences and are characterized by factors of their formation

Excited-state absorption spectra of Pr³⁺ ions doped into LiY<inf>0.3</inf>Lu<inf>0.7</inf>F<inf>4</inf> mixed crystal

© 2016 Optical Society of America.The UV/visible polarized excited-state absorption (ESA) spectra from the 1D2 and 3Pj manifolds of 4f2-configuration of Pr3+ ions doped into LiY0.3Lu0.7F4 mixed crystal were studied at room temperature. The data about ESA cross-sections are necessary to estimate an efficiency of stepwise excitation of 4f5d-states of Pr3+ ions in these crystals

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

Photoconductivity and photodielectric effect in LiY1 - X Lu x F4 crystals doped with Ce3+ and Yb 3+ ions

Time and spectral dependences of the dielectric permittivity of the LiY1 - x Lu x F4 (x = 0, 0.5, and 1) crystals doped with Ce3+ and co-doped with Yb3+ ions under UV laser excitation were studied by the 8-mm microwave resonant technique at room temperature. The obtained photoconductivity spectrum in 240-310 nm spectral range was interpreted as a stepwise photoionization spectrum of the Ce 3+ ions due to sequential 4f-5d and 5d-6s transitions. Average lifetimes of free and defect trapped (color centers) charge carriers were estimated. © 2014 Pleiades Publishing, Ltd

Procedure for interpreting the luminescence lines caused by ordinary and cross-relaxation transitions

A procedure using a spectrometer with a CCD detector for interpreting the luminescence lines caused by ordinary and cross-relaxation transitions is presented for LaF3 crystal activated by Pr3+ ions as example. © 2013 Pleiades Publishing, Ltd

Polishing surface layer of LiYF4 single crystal

By using methods of optical microscopy, microhardness and fast electrons diffraction in reflection mode it was determined that after mechanical polishing the depth of distorting layer is about 30 μm. Optimal results for layer etching were obtained by using KOH at 60°. The distortionless surface at LiYF4 single crystal was produced by mechanical polishing with chemical and ion-beam etching

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