Structure, morphology, and nonlinear optical properties of orthorhombic α-Ca(HCOO)₂ single crystals

Nonlinear optical α-Ca(HCOO)2 crystals were synthesized by the solution evaporation growth method. The crystals with good transparency in the visible light region were grown with a maximum size of 7 mm × 6 mm × 4 mm and were studied using single crystal X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FT-IR), and FTIR-Raman spectroscopy. The crystals are orthorhombic with a space group of Pbca having unit-cell dimensions a = 10.238(4) A, b = 6.305(2) A, c = 13.456(5) A, α = β = γ = 90°, V = 868.6(5) A3, and Z = 8. The as-grown crystals exhibit polyhedral morphology consisting of {210}, {111}, and {100} facets. The nonlinear absorption property of the crystals was explored by open-aperture Z-scan measurements under the excitation of femtosecond laser pulses at the wavelength of 800 nm. The α-Ca(HCOO)2 crystals exhibit saturable absorption. The effective nonlinear absorption coefficient under the low-intensity approximation is discovered to be β = −5.09 cm/GW.