HgB₂S₄: A d¹⁰ Metal Thioborate with Giant Birefringence and Wide Band Gap

Abstract

Birefringent crystals are important optical devices in various advanced optical systems because they can create and control polarized light. In this work, the capability of planar [B 3 S 6 ] to produce large birefringence was theoretically studied for the first time. Moreover, the first d 10 metal thioborate HgB 2 S 4 (HBS) has been synthesized successfully, which was constructed by the π-conjugated [B 3 S 6 ] and [HgS 2 ] units. Notably, HBS shows great potential to be an infrared birefringent material due to its large birefringence, Δn = 0.52 @ 1064 nm (∼4.3 × α-BaB 2 O 4 and ∼10.4 × AgGaS 2 @ 1064 nm), wide band gap of 3.36 eV, and wide transparent window (∼0.37−25 μm). To the best of our knowledge, both the birefringence and the band gap of HBS are the largest among mercury sulfides. Structure-performance analyses reveal that the π-conjugated [B 3 S 6 ] units are the main birefringence contributor and could be regarded as a good unit for designing IR birefringent materials. This work will provide direct guidance to design high performance birefringent crystals in the future.

HgBr2: an easily growing wide-spectrum birefringent crystal

“…[32][33][34][35][36] In borates, the linear unit [BO 2 ] is thought to have greater polarizability anisotropy than the classic [BO 3 ], 37,38 and the previous studies of HgB 2 S 4 and trigonal HgS have suggested that the [S-Hg-S] linear units have strong birefringent contributions (0.28 at 1064 nm and 0.29 at 2100 nm, respectively). 39,40 Moreover, the [X-Hg-Hg-X] motif in the binary mercurous halide can induce a giant birefringence; however, prolonged exposure to light can lead to decomposition of mercurous halide. 41 Therefore, the linear [X-Hg-X] unit can also be regarded as a potential emerging building block of birefringent materials; however, its comprehensive investigation remains insufficient.…”

Na6Mg3P4S16 and RbMg2PS4Cl2: two Mg-based thiophosphates with ultrawide bandgaps resulting from [MgS6] and [MgSxCl6−x] octahedra

“…1–5 Wide-bandgap oxide semiconductors have been intensely investigated, in particular for their outstanding properties of high transparency in the ultraviolet (UV)/deep-UV region, 6–15 with examples including KBe 2 BO 3 F 2 (KBBF), 16 LiB 3 O 5 (LBO), 17 KH 2 PO 4 (KDP) 18 and KTiOPO 4 (KTP). 19 Chalcogenides are generally recognized as one of the most capable sources for investigating infrared (IR) functional materials due to their structural diversity and wide IR-transparent ranges, 20–40 which may encompass the critical IR atmospheric windows 3–5 and 8–12 μm, with examples of these chalcogenides including the well-known chalcopyrite-type crystals AgGaQ 2 (Q = S, Se) and ZnGeP 2 . 41–43 However, their applications have been limited by the low laser-induced damage threshold (LIDT) for AgGaQ 2 (AGS, AGSe) and the strong absorptions at about 1–2 μm for ZnGeP 2 , which may be caused by their narrow bandgaps.…”

EuSi7P10: An Inorganic Supramolecular Nonlinear Optical Crystal Exhibiting Strong Second-Harmonic Generation Response

“…Second-order nonlinear optical (NLO) materials hold significant relevance for laser communication and optoelectronic devices, owing to their utility as innovative laser sources for frequency conversion. − In particular, mid-infrared (mid-IR, 3–25 μm) NLO materials play an important role in signal communication, noninvasive medical diagnostics, and laser guidance. − At present, commercially available IR NLO materials are predominantly composed of chalcopyrite-type compounds, including AgGaS 2 (AGS), AgGaSe 2 (AGSe), and ZnGeP 2 (ZGP). − These materials are noted for their substantial second-harmonic generation (SHG) responses and broad IR transparency. However, they possess inherent disadvantages such as a low laser damage threshold (LDT) and two-photon absorption (TPA), which significantly impede their further utilization in high-power lasers.…”