Self-frequency doubled green NdxY1-xCa4O(BO3)3 laser

Nd-doped yttrium calcium oxyborate, Nd x Y 1-x Ca 4 O(BO 3 ) 3 (NYCOB), was grown using pulling from the melt, with large sizes and good optical quality as well as different Nd 3+ -ion densities of 0 to 10 at% in the lattice structure. These crystals belong to the monoclinic system with point group m, conforming space group C m . The unit cell constants were a = 0.8076(7), b = 1.6020(10), and c = 0.3527(2) nm for a Nd 3+ content of 8 at%, with β = 101.23°, and z = 2. The measured absorption of the NYCOB was compared to Judd-Ofelt (JO) theory. When applied, the JO theory of parity-forbidden electric-dipole transitions of rare earth ions on non-centrosymmetric sites demonstrates good agreement. The polarized absorption coefficients at 811 nm were calculated as α X = 1.59, ay = 1.75, and α Z = 2.02 1/cm, respectively. The valence-conduction band gap is about 5.39 eV. The fitted intensity parameters Ω t (t = 2, 4, and 6) were 3.51×10 -20 , 7.82×10 -20 , and 3.79×10 -20 cm 2 , with a root-mean square deviation of 6.30 x 10 -21 cm 2 . The emission properties of the excited 4 F 3/2 state with the level lifetime of 216.67 μs were studied, which exhibit the two pass bands of laser for possible applications in practice. The self-frequency doubling tests are interesting. A very low threshold power of 2 mW for a sample with average Nd 3+ content of 7 at%, length of 6 mm, and phase matching angles of 0 = 64.5° and φ = 35.5° have been measured. The measured output power of green light was 19.4 mW accompanied with a conversion efficiency of 3.7%.