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Large-size Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) based ferroelectric single crystals have been grown successfully by the vertical Bridgman method for application in the field of high-end piezoelectric devices. The piezoelectric and dielectric performance uniformity of PMN-PT based ferroelectric crystals is a critical application requirement. Recently, alternating current poling (ACP) has attracted much attention due to its low cost and high efficiency in improving the piezoelectric properties of PMN-PT based crystals. Here, we report the comparison of the performance fluctuation of direct current poling (DCP) and ACP Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) ferroelectric single crystals grown in the [110] direction using the vertical Bridgman method. The fluctuation of piezoelectric coefficient d33, dielectric constant ɛT33/ɛ0, and dielectric loss tanδ was presented. We found that the average d33 and ɛT33/ɛ0 of ACP samples are 1290 and 1500 pC/N and 3890 and 4290 for two different wafers, which were 18% and 23%, 21% and 26% higher than DCP samples. The tanδ of ACP samples was much lower than that of DCP samples. The DCP and ACP samples exhibited the close data of the fluctuation ratios of d33 and ɛT33/ɛ0. The fluctuation ratios of d33 and ɛT33/ɛ0 for DCP and ACP samples are all less than 10%. This work offers a reference for practical ACP technique applications. [ABSTRACT FROM AUTHOR]

Three Mg-containing borates were obtained by high-temperature spontaneous crystallization. In the (A2O)- or (A2O-MO)-MgO-B2O3 system (A is alkali metal and M is alkaline-earth metal) reported in the ICSD, Li4Mg3SrB12O24 is the first compound that contains one-dimensional infinite anionic chains, and the two examples of the isostructural A2Mg3B16O28 (A = Rb, Cs) exhibit a two-dimensional infinite bilayer structure for the first time, which contributes to the enrichment of the structural chemistry of Mg-containing borates. Besides, the results of comparison and analysis in this system clearly show that Mg not only affects the anionic frameworks of borates to produce low-dimensional structures but, together with the ratio of Ncation/NB, is responsible for the dimensionalities of the anionic frameworks in borates. The optical properties of the three compounds also show that they all have short cutoff edges, and Cs2Mg3B16O28, in particular, could reach the deep-ultraviolet region (<200 nm). [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) crystals that can generate deep‐ultraviolet (DUV) lasers by the frequency conversion processes play an important role in many basic and frontier research fields. Tetrahedron‐based NLO crystals, which are decent DUV NLO candidates, always exhibit a large DUV transparency window. However, their insufficient birefringence often makes it difficult to satisfy the phase matching condition in the DUV or even UV region. Therefore, some strategies are put forward to improve the phase matching ability of tetrahedron‐based DUV NLO crystals. In this review, the relevant reports are summarized into four categories, including the heterozygosity of tetrahedral groups, the introduction of the planar groups, the combination of the heteroleptic tetrahedrons and the planar groups, and the recombination of polar structures with ferroelectricity. Furthermore, the development tendency of tetrahedron‐based DUV NLO crystals is also discussed. Therefore, this review will be helpful to the exploration of new DUV NLO crystals. [ABSTRACT FROM AUTHOR]

Phase-matching of light waves is a critical condition for maximizing the efficiency of nonlinear frequency conversion processes in nonlinear optical crystals; however, phase-matching, commonly achieved by tuning birefringence, is often difficult to achieve over a wide wavelength range. Here, full-wavelength phase-matching crystals that can avoid phase-mismatching across the entire optical transparency range are proposed. The anisotropic strength of bonding in the dimension of energy is confirmed theoretically to be the key to the full-wavelength phase-matching ability. We demonstrate that a crystal of guanidinium tetrafluoroborate (C(NH2)3BF4) can be phase-matched throughout its entire optical transparency range and is able to generate harmonic light as short as ~193.2 nm, which is close to its deep-ultraviolet cut-off edge. Importantly, this crystal is stable, cheap and efficient compared with commercially available nonlinear optical crystals for generation of 266 nm light. This work lays the foundation for finding a new class of crystals in which the phase-matching wavelength fully covers its optical transparency range, and also provides a high-performance crystal for generating light at 266 nm—the fourth-harmonic of a commercial 1,064 nm laser. A new nonlinear optical crystal offers efficient harmonic generation in the ultraviolet and deep-ultraviolet regions. [ABSTRACT FROM AUTHOR]