KMg(H₂O)PO₄: A Deep-Ultraviolet Transparent Nonlinear Optical Material Derived from KTiOPO₄

Abstract

Discovery of new nonlinear optical (NLO) crystals, especially crystals that can produce coherent light in the deep-ultraviolet (DUV) region is essential for the development of diverse fields. Here, we successfully discovered and synthesized a new DUV transparent NLO crystal KMg(H 2 O)PO 4 (KMP) using KTiOPO 4 (KTP) as a template through substituting TiO 6 by the MgO 5 (H 2 O) group. Its structure constructed by 2D [MgPO 5 ] ∞ infinite layers in which PO 4 groups arrange orderly leads to KMP exhibiting a large second harmonic generation (SHG) efficiency (≈1.14 × KDP) which is similar to KBe 2 BO 3 F 2 (1.2 × KDP). Moreover, the ultraviolet cut-off edge of KMP is blue-shifted to <200 nm from 350 nm of KTP after replacing the transition metal cations Ti 4+ by alkaline-earth metal cations Mg 2+ . First principle calculations reveal that the SHG efficiency of KMP was significantly contributed by PO 4 groups, and contributions from cations are negligibly small which agrees well with the anion group theory.

M(NH2SO3)2 (M=Sr, Ba): Two Deep‐Ultraviolet Transparent Sulfamates Exhibiting Strong Second Harmonic Generation Responses and Moderate Birefringence

“…The results showed that the birefringence of SNSO is 0.056 and 0.058 at 589.3 and 532 nm, respectively (Supporting Information, Table S5, Figure S8), which is the largest value for DUV sulfamates to date. In addition, the birefringences of both compounds are larger than most of the DUV NLO crystals containing traditional isotropic tetrahedral units, such as KMg(H 2 O)PO 4 (0.018@532 nm), [35] RbBa 2 (PO 3 ) 5 (0.009@1064 nm), [20] KLa-(PO 3 ) 4 (0.008@1064 nm), [36] CsLa(PO 3 ) 4 (0.006@1064 nm), [37] K 4 Mg 4 (P 2 O 7 ) 3 (0.0108@1064 nm), [22] Rb 4 Mg 4 (P 2 O 7 ) 3 (0.009@1064 nm) [22] and K 2 SrP 4 O 12 (0.016@1064 nm), [38] and comparable to recently reported DUV NLO crystals containing anisotropic tetrahedral units including (NH 4 ) 2 PO 3 F (0.035@532 nm), [30] [C(NH 2 ) 3 ] 2 PO 3 F (0.039@532 nm) [30] and NaNH 4 PO 3 F•H 2 O (0.035@532 nm). [30] The powder SHG responses of SNSO and BNSO were measured under the fundamental wave laser radiation (l = 1064 and 532 nm) respectively using polycrystalline KDP and b-BBO as the reference.…”

Ba3Sb2(PO4)4 and Cd3Sb2(PO4)4(H2O)2: Two New Antimonous Phosphates with Distinct [Sb(PO4)2] Structure Types and Enhanced Birefringence

“…The inorganic optical materials, including borates, − phosphates, − iodates, − and tellurites, , have received unprecedented attention since the advent of laser technology. Phosphates, as an evergreen in the field, have been employed on optical components as early as the 1960s. ,, Inorganic phosphates have the following advantages: (1) the fundamental building block of PO 4 tetrahedron is noncentrosymmetric (NCS), which is beneficial to the formation of NCS structures; − (2) the PO 4 tetrahedra can be condensed further into numerous building units, from 0D clusters to 3D frameworks, resulting the diverse structural types of phosphates; ,− (3) the PO 4 group is transparent in UV bands, which make phosphates an efficient candidate for UV or even DUV optical materials; − (4) the phosphate derivatives are very rich, such as fluorophosphates, − borophosphates, − tellurite phosphates, − and so on, which have widened the phosphate systems greatly. However, each coin has two sides.…”

Linear and Nonlinear Optical Properties of Centrosymmetric Sb4O5SO4 and Noncentrosymmetric Sb4O4(SO4)(OH)2 Induced by Lone Pair Stereoactivity

“…Lasers with different wavelengths are widely applied in both civil and military fields, such as precision manufacturing, laser medicine, remote communication, optoelectronic devices, and so forth. − Nonlinear optical (NLO) materials can achieve the tunable laser output by frequency conversion and are of great interest for scientists. − Over the past few decades, some commercial NLO crystals, such as AgGaX 2 (X = S, Se), , ZnGeP 2 , KTiOPO 4 , KH 2 PO 4 , β-BaB 2 O 4 , LiB 3 O 5 , have been developed. However, with the development of technologies, these crystals cannot satisfy the increasing requirements of frequency conversations in the whole wavelength region.…”

“…Recently, the non-π-conjugated systems as promising NLO candidates attracted high interest for researchers. For example, as structural units, PO 4 tetrahedra have been used to construct a series of excellent phosphates optical materials. ,− However, it is notable that sulfates, which are also composed of non-π-conjugated tetrahedral units (SO 4 tetrahedra), are in the initial stage in the exploitation of NLO materials. Hence, the exploration of the sulfates NLO materials is challenging but significantly important.…”