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We report on growth and detailed spectroscopic study of Eu 3+ -doped tetragonal sodium gadolinium double tungstate, Eu:NaGd(WO 4 ) 2 , a new promising crystal for deep-red lasers. Large-volume crystal doped with 4.9 at.% Eu is grown by Czochralski method along the [001] crystallographic direction. Absorption of Eu 3+ ions is studied at room temperature (RT) and at 6 K. For the absorption band related to the 7 F 1 → 5 D 1 transition suitable for pumping of Eu:NaGd(WO 4 ) 2 , the maximum cross-section is σ abs = 1.2 × 10 −21 cm 2 at 535.5 nm with the full width at half maximum (FWHM) of 3.1 nm (at RT, for E || a polarization). For the 5 D 0 → 7 F 4 transition, the maximum stimulated-emission cross-section is σ SE = 1.6 × 10 −21 cm 2 at 698.3 nm (RT, E || c polarization). Lifetime of the 5 D 0 state is 490 ± 10 μs (at RT). Under UV excitation, Eu:NaGd(WO 4 ) 2 provides intense red emission with CIE coordinates ( x = 0.671, y = 0.329). [ABSTRACT FROM AUTHOR]

Abstract: Monoclinic 2at% Eu-doped KY(WO4)2 is grown by top-seeded solution growth method. Polarization-resolved absorption and stimulated-emission cross-section spectra are determined for this crystal. Spectroscopic properties of Eu:KY(WO4)2 are modeled within conventional Judd–Ofelt theory, as well as theory of f–f transition intensities for systems with anomalously strong configuration interaction, yielding absorption oscillator strengths, luminescence branching ratios and radiative lifetime of 5D0 state. The impact of excited-state absorption from this state on possibility of laser operation is discussed. Photoluminescent properties of Eu:KY(WO4)2 are determined. This crystal provides intense red emission with CIE coordinates x=0.670, y=0.329. [Copyright &y& Elsevier]

Abstract: Pure and Nd-doped disordered calcium vanadate Ca10K(VO4)7, Ca10Li(VO4)7, Ca9La(VO4)7 and Ca9Y(VO4)7 single crystals with high optical quality were grown by Czochralsky technique in inert atmosphere. Their polarized absorption spectra were investigated in details. Spectroscopic parameters for Nd3+ ion were determined with Judd–Ofelt theory (J–O) and theory of f–f transition intensities for systems with intermediate or anomalously strong configuration interaction (ICI or ASCI approximation). Spectral and temporal characteristics of luminescence associated with 4F3/2→4I9/2, 4I11/2 and 4I13/2 transitions were analyzed, luminescence branching ratios and radiative lifetimes were calculated. Thermal expansion coefficients were determined for Ca9La(VO4)7 and Ca9Y(VO4)7 crystals in the directions of a and c crystallographic axes. Principal thermo-optic coefficients dn o/dT and dn e/dT were measured for Ca9La(VO4)7 crystal in the spectral range of 0.4–1.1μm. The potential of disordered vanadates for laser applications was analyzed from the point of thermal effects. [Copyright &y& Elsevier]

Monoclinic Ho:KY(WO 4 ) 2 crystals doped with up to 7.5 at.% Ho are grown by the Top Seeded Solution Growth-Slow Cooling method. The evolution of their unit cell parameters in dependence on the Ho doping and temperature is studied. The polarized low-temperature (6 K) optical absorption of the Ho 3+ ion is investigated in detail to determine the energy of the Stark sub-levels. Room-temperature absorption, stimulated-emission and gain cross-section spectra of Ho:KY(WO 4 ) 2 crystals are derived for polarizations parallel to the principal optical axes, E || N p , N m and N g . The maximum absorption cross-section for the 5 I 8 → 5 I 7 transition is 1.60×10 −20 cm 2 at 1961.0 nm and the maximum stimulated-emission cross-section for the 5 I 7 → 5 I 8 transition is 2.65×10 −20 cm 2 at 2056.3 nm (for E || N m ). The radiative lifetime of the upper laser level of the Ho 3+ ion ( 5 I 7 ) amounts to 4.8 ms. Continuous-wave Ho 3+ laser operation is achieved under in-band pumping by a Tm laser at 1946 nm. In the microchip configuration, the maximum output power reached 205 mW at 2105 nm with a slope efficiency as high as 85%. [ABSTRACT FROM AUTHOR]