Growth and spectral characteristics of a new promising stoichiometric laser crystal: Ca9Yb（VO4）7

A Ca9Yb(VO4)7 crystal with dimensions of Φ23 mm×35 mm was grown successfully by Czochralski method. Its thermal conductivity was 1.06 W/(m?K) at room temperature. The absorption cross-sections at 980 nm were 1.80×10–20 cm2 and 1.28×10–20 cm2 for π- and σ- polarizations, respectively, with a full-width at half-maximum of 34 nm. The crystal had a broad emission at around 1025 nm with a full-width at half-maximum of 67 nm for π- polarization and 70 nm for σ- polarization. The emission cross-sections of the crystal were calculated by using reciprocity method and Füchtbauer-Ladenburg formula. The emission cross-sections at 1025 nm were 3.57×10–20 cm–2 and 1.91×10–20 cm–2 for π- and σ- polarization, respectively. The fluorescence lifetime was 332 μs. The results indicated that the crystal is a promising femtosecond and tunable laser material.     

沿海地区真空联合堆载预压施工方法

本方法在实施真空预压法的同时在地基上部进行堆载,能够同时发挥真空预压和堆载预压各自的优势,使土体压缩的更加密实,沉降量更大,土体的物理力学性质得到更好的改善,可提高加荷速率、缩短工期,使地基沉降在施工期内得以基本完成,从而有效减少地基工后沉降。