The systematic modification of the molecular structure of nonlinear optical (NLO)-active materials is a very attractive approach to the improvement of NLO performance. In this study, one lutetium selenite compound Lu(SeO3)(HSeO3)(H2O)•(H2O) (1) was synthesized by hydrothermal means, while a further two lutetium selenites Lu3F(SeO3)4 (2) and Lu(SeO3)(NO3)(H2O) (3) were successfully synthesized by anion partial substitution (APS) of the parent structure 1 under hydrothermal conditions. Specifically, substitution of the [HSeO3] − anions in the noncentrosymmetric 1 by F − or [NO3] − anions with differing denticity leads to the formation of polar 2 and centrosymmetric 3. Our study reveals that the denticity of the secondary functional anions has a significant influence on the coordination environments of the rare-earth metal cation Lu 3+ and consequently the molecular configuration and NLO performance of the resultant multidimensional selenites. In contrast to 1, which displays a weak second-harmonic generation (SHG) response (0.1 × KH2PO4 (KDP)), 2 exhibits a greatly improved NLO performance, including a strong SHG signal (2.5 × KDP, the highest value among rare-earth-metal-based NLO selenites), a wide band gap (3.57 eV) and optical transparency window (0.35−10.3 μm), high thermal stability (~550 °C), and a large laser damage threshold (36 × AgGaS2). These results suggest that 2, as the first example of a fluorinated lutetium selenite, is a strong NLO candidate crystal spanning a region from the near-ultraviolet to the mid-infrared. These APS studies highlight a new feasible approach towards highperformance NLO crystals.
Study of mid-infrared (mid-IR) nonlinear optical (NLO) materials is hindered by the competing requirements of optimizeds econd-harmonic generation (SHG) coefficient d ij and laser-induced damage threshold (LIDT) as well as the harsh synthetic conditions.H erein, we report facile hydrothermal synthesis of ap olar NLO vanadate Cs 4 V 8 O 22 (CVO) featuring aq uasi-rigid honeycomb-layered structure with [VO 4 ]a nd [VO 5 ]p olyhedra aligned parallel. CVOp ossesses aw ide IR-transparent window,h igh LIDT,a nd congruentmelting behavior.I th as very strong phase-matchable SHG intensities in metal vanadate family (12.0 KDP @1 064 nm and 2.2 AGS@2100 nm). First-principles calculations suggest that the exceptional SHG responses of CVOl argely originate from virtual electronic transitions within [V 4 O 11 ] 1 layer;t he excellent optical transmittance of CVOa rises from the special characteristics of vibrational phonons resulting from the layered structure.
A new alkali metal-rare earth metal sulfate with the formula NaY(SO4)2.H2O has been synthesized using a mild hydrothermal method. It crystallizes in the noncentrosymmetric trigonal space group P3121 (No. 152)...
Introduction of rare-earth cations with moderate electropositivity into the iodate system afford three noncentrosymmetric rare-earth iodates REn(IO3)3n(H2O) with optimized balance between SHG efficiency and optical band gaps.
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