Two new biaxial, diamond-like semiconductors, Li₂CdGeSe₄ and Li₂CdSnSe₄, were prepared via high-temperature, solid-state synthesis. Single crystal X-ray diffraction and X-ray powder diffraction coupled with Rietveld refinement were used to refine the crystal structures and assess the phase purity, respectively. Both compounds adopt the lithium cobalt(II) silicate structure type. Strong second-order nonlinear optical (NLO) susceptibility, phase matchability, relatively high thermal stability, and excellent transparency deem both materials potential infrared (IR) NLO candidates. Li₂CdGeSe₄ and Li₂CdSnSe₄ display optical bandgaps of approximately 2.5 and 2.2 eV, respectively. Li₂CdSnSe₄ exhibits a strong, red-light emission under 1064 nm excitation, allowing the compound to release energy that accumulates by two-photon absorption under Nd:YAG laser radiation. Therefore, Li₂CdSnSe₄ shows a high laser-induced damage threshold (LIDT) of 0.7 GW cm⁻². This special phenomenon is remarkable and may open a new avenue in searching for promising IR NLO materials with large LIDTs.

中文翻译：

---

Li ₂ CdGeSe ₄和Li ₂ CdSnSe ₄：具有强红外二阶响应和受光致发光影响的激光损伤阈值的双轴非线性光学材料

通过高温固态合成，制备了两种新型的双轴类金刚石半导体Li ₂ CdGeSe ₄和Li ₂ CdSnSe ₄。单晶X射线衍射和X射线粉末衍射结合Rietveld精炼技术分别用于精炼晶体结构和评估相纯度。两种化合物均采用硅酸钴锂（II）结构类型。强大的二阶非线性光学（NLO）磁化率，相匹配性，相对较高的热稳定性和出色的透明性均认为这两种材料都是潜在的红外（IR）NLO候选材料。Li ₂ CdGeSe ₄和Li ₂ CdSnSe_4个显示带隙分别约为2.5 eV和2.2 eV。Li ₂ CdSnSe ₄在1064 nm激发下显示出强烈的红光发射，从而使该化合物释放出在Nd：YAG激光辐射下通过双光子吸收而积累的能量。因此，Li ₂ CdSnSe ₄显示出0.7 GW cm ^-2的高激光诱导损伤阈值（LIDT）。这种特殊现象非常显着，可能会为寻找具有大LIDT的有希望的IR NLO材料开辟新的途径。