Properties of Nd^3+-doped and undoped tetragonal PbWO_4, NaY(WO_4)_2, CaWO_4, and undoped monoclinic ZnWO_4 and CdWO_4 as laser-active and stimulated Raman scattering-active crystals

Abstract

Spectroscopic, laser, and χ⁽³⁾ nonlinear optical properties of tetragonal PbWO₄, NaY(WO₄)₂, CaWO₄, and monoclinic CdWO₄ and ZnWO₄ were investigated. Particular attention was paid to Nd³⁺-doped and undoped PbWO₄ and NaY(WO₄)₂ crystals. Their absorption and luminescence intensity characteristics, including the peak cross sections of induced transitions, were determined. Pulsed and continuous-wave lasing in the two ⁴ F _3/2→ ⁴ I _11/2 and ⁴ F _3/2 →⁴ I _13/2 channels was excited. For these five tungstates, highly efficient (greater than 50%) multiple Stokes generation and anti-Stokes picosecond generation were achieved. All the observed scattered laser components were identified. These results were analyzed and compared with spectroscopic data from spontaneous Raman scattering. A new crystalline Raman laser based on PbWO₄ was developed for the χ⁽³⁾ conversion frequency of 1-µm pump radiation to the first Stokes emission with efficiency up to 40%. We classify all the tungstates as promising media for lasers and neodymium-doped crystals for self-stimulated Raman scattering lasers.