Growth, thermal, and polarized spectral properties of the Sm:GdCa4O(BO3)3 crystal for a reddish-orange laser

Abstract

A new Sm-doped calcium oxyborate crystal, Sm_xGd_1−xCa₄O(BO₃)₃ (Sm:GdCOB), was grown by the Czochralski (Cz) method. The cell parameters were determined to be a = 8.0910 Å, b = 16.0090 Å, c = 3.5571 Å, β = 101.267°, and Z = 2 with the Cm space group. The density was determined to be 3.72 g cm⁻³ by the Archimedes method. The thermal properties, including thermal expansion coefficient, the thermogravimetric and differential thermal analysis (TG-DTA) as well as specific heat were investigated systematically. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay lifetimes of the Sm:GdCOB crystal were measured at room temperature. Based on the J–O theory, various spectra parameters, such as polarized absorption cross-section, intensity parameters, transition probabilities, radiative lifetime, and branching ratios were obtained, and the polarized stimulated emission cross-sections were determined. For the Sm:GdCOB crystal, excellent physical properties, such as rapid growth with large size, high specific heat (0.585 J g⁻¹ K⁻¹, RT), large quantum yield (76%), and strong emission around 600 nm predict potential application as a reddish-orange laser medium. In addition, the Sm:GdCOB crystal exhibits a distinct saturable absorption characteristic at 1064 nm, indicating that it can be used as a pulse modulation material in the solid-state laser.