Yaoguo Shen

Designing a Beryllium-Free Deep-Ultraviolet Nonlinear Optical Material without a Structural Instability Problem

A beryllium-free deep-ultraviolet (deep-UV) nonlinear optical (NLO) material K3Ba3Li2Al4B6O20F is developed mainly by the element substitution of Be for Al and Li from Sr2Be2B2O7 that was considered as one of the most promising deep-UV NLO materials. K3Ba3Li2Al4B6O20F preserves the structural merits of Sr2Be2B2O7 and thus exhibits no layering growth tendency and possesses the optical properties required for deep-UV NLO applications, including deep-UV transparency, phase-matchability, and sufficiently large second-harmonic generation (1.5 × KH2PO4). Furthermore, it overcomes the structural instability problem of Sr2Be2B2O7, which is confirmed by the obtainment of large single crystals and phonon dispersion calculations. These attributes make it very attractive for next-generation deep-UV NLO materials. The substitution of Be for Al and Li in beryllium borates provides a new opportunity to design beryllium-free deep-UV NLO materials with good performance.

Broad-Band-Emissive Organic–Inorganic Hybrid Semiconducting Nanowires Based on an ABX3-Type Chain Compound

Organic-inorganic hybrid lead halide (e.g., CH3NH3PbX3, where X = CI, Br, and I) nanowires (NWs) with remarkable electric and optical properties have recently garnered increasing attention, owing to their structural flexibility and tunability compared to inorganic semiconducting NWs. While most recently reported NWs are limited to methylammonium/formamidinium three-dimensional lead halide perovskites, it is urgent to develop new organic-inorganic hybrid semiconducting NWs. Here, broad-band-emissive single-crystal semiconductive NWs based on a new ABX3-type organic-inorganic chain hybrid, (2-methylpiperidine)lead tribromide, are reported. It is believed that this work will enrich the organic-inorganic hybrid semiconducting NWs and may provide potential applications for LED displaying.

A beryllium-free deep-UV nonlinear optical material CsNaMgP2O7 with honeycomb-like topological layers

Few nonlinear optical (NLO) materials are available for deep-UV second-harmonic generation (SHG), limited by the fundamental requirements of the structure-directing optical properties. KBe2BO3F2 is the sole exception, but it suffers from the high toxicity of the compositional beryllium element and a serious layering growth tendency. Here, we report a beryllium-free deep-UV NLO phosphate with honeycomb-like topological structural layers, namely, CsNaMgP2O7. The phosphate exhibits an enhanced SHG response of 1.1 times that of KH2PO4, which is comparable to that of KBe2BO3F2. Based on theoretical analysis, the enhanced SHG response can be well rationalized. Meanwhile, CsNaMgP2O7 possesses a reinforced interlayer bonding of about 2.95 times that of KBe2BO3F2, which is very favorable to mitigate the layering growth tendency. This work will be helpful to better understand the structure–property relationships in deep-UV NLO materials.

A new phase-matchable nonlinear optical silicate: Rb2ZnSi3O8

Nonlinear optical (NLO) crystals are key materials for generation of coherent light in solid state lasers. A new NLO material Rb2ZnSi3O8 is synthesized by the traditional solid-state reaction technique and its crystals are obtained by spontaneous crystallization using an Rb2O–B2O3 flux. It crystallizes in an asymmetric space group of C2 (No. 5) and features a three-dimensional framework composed of SiO4 and ZnO4 tetrahedral groups. Remarkably, it exhibits a phase-matchable powder second harmonic generation approximately 2.5 times that of α-SiO2, which is well known to be non-phase-matchable. The first-principle calculations reveal that the Si–O and Zn–O tetrahedra determine the optical properties in the Rb2ZnSi3O8 crystal and may be the origin of the phase matching behavior in Rb2ZnSi3O8. The UV-visual-near-infrared diffuse reflectance spectrum shows that Rb2ZnSi3O8 has a wide transparency window down to the deep-UV spectral region. In addition, Rb2ZnSi3O8 is non-hygroscopic. These results suggest that Rb2ZnSi3O8 is a potential deep-UV NLO crystal.

An optoelectronic duple bistable phosphate with ultrahigh thermal stability

Bistable compounds have attracted intensive interest because of their great potential to realize seamless integration of multifunctional switches in one device. However, previous studies are mainly limited to organic–inorganic hybrid compounds, which have relatively low phase-transition temperature and thermal stability. Here, we report a new pure inorganic compound CsCdPO4, which undergoes a high-temperature phase transition at 447 K. Correspondingly, CsCdPO4 simultaneously shows an interesting duple bistability of nonlinear optical and dielectric properties. Furthermore, it shows an extremely high thermal stability up to 1418 K, which is significantly higher than those of organic–inorganic bistable compounds. This work will open up a new avenue to develop multifunctional materials that remain stable even under extreme operating conditions (e.g. extremes of temperature).