Rb_21.89W_32.66O₁₀₈: An Excellent Mid- and Far-IR Nonlinear-Optical Material with a Wide Band Gap

IR nonlinear-optical (NLO) crystal is the important device in IR laser technology. Nevertheless, the application of most IR NLO crystals in high-power lasers is always limited by the low laser damage threshold (LDT), which is mainly caused by the narrow optical band gap (E_g). Here, the physical properties of the Rb_21.89W_32.66O₁₀₈ (RWO) crystal with a longer absorption cutoff edge and a wide E_g were systematically studied for the first time. A preliminary measurement of the LDT was performed, and the result shows that RWO has a high powder LDT of about 42 times that of AgGaS₂. In order to better understand the relationship between the structure and properties, the dipole moments of WO₆ octahedra were accurately calculated and analyzed. Meanwhile, it was indicated that RWO exhibits an ideal frequency doubling strength with the type I phase matching. Finally, it was revealed that RWO has great application value as an IR NLO crystal.