Strong SHG Responses in a Beryllium‐Free Deep‐UV‐Transparent Hydroxyborate via Covalent Bond Modification

Abstract

Deep-ultraviolet (deep-UV) nonlinear optical (NLO) crystals are key materials in creating tunable deep-UV lasers for frequency conversion technology.H owever, practical application of the sole usable crystal, KBe 2 BO 3 F 2 ,has been hindered by the high toxicity of beryllium and its layering tendency in crystal growth. Herein, we report aberyllium-free deep-UV NLO material NaSr 3 (OH)(B 9 O 16 )[B(OH) 4 ] (NSBOH), synthesized by ac ovalent bond modification strategy under hydrothermal conditions.M oisture-stable NSBOH exhibits strong second-harmonic generation (SHG) at 1064 nm (3.3 KH 2 PO 4 )a nd 532 nm (0.55 b-BaB 2 O 4 ), both amongst the largest powder SHG responses for ad eep-UV borate,w ith good phase-matchability and as hort wavelength cutoff edge (below1 90 nm). NSBOH possesses a3 D covalent anionic [B 9 O 19 ] 1 honeycomb-like framework with no layering. The Sr 2+ and Na + ions,residing in the cavities of the anionic framework, act as templates for the assembly and favorable alignment of NLO-active groups,r esulting in an optimal balance between strong SHG activities and wide UV transparency.These merits indicate NSBOH is avery attractive candidate for deep-UV NLO applications.

[Sr4Cl2][Si3S9]: Ultrawide-bandgap salt-inclusion thiosilicate nonlinear optical material with unprecedented tri-polymerized [Si3S9] clusters

“…Infrared nonlinear optical (IR NLO) materials have been developed as indispensable devices in tunable lasers for extensive military and civil applications. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Chalcogenides exhibiting good SHG responses and wide IR transmission ranges have enjoyed extensive applications in IR laser frequency conversion fields, such as the famous chalcopyrite-type crystals: AgGaQ 2 (Q = S, Se) and ZnGeP 2 , but their applications have been limited to date by their innate performance drawbacks. [20][21][22] An outstanding IR NLO material should satisfy the following critical prerequisites: (i) a wide optical bandgap (E g ), improved resistance to laser damage, for potential applications in high-energy laser system; (ii) large second-harmonic-generation (SHG) response (d ij ), to maintain a good laser-conversion efficiency for high-power output; (iii) long IR absorption cut-off edge, which should cover the two important atmospheric windows (3-5 mm and 8-12 mm) for laser remote transmission.…”

AgGaSe2-Inspired Nonlinear Optical Materials: Tetrel Selenides of Alkali Metals and Mercury

“…Nonlinear optical (NLO) materials have shown the huge application potential as practical candidates in the tunable solid-state lasers. − Metal oxides and halides with short absorption cutoff edges and good second harmonic generation (SHG) responses basically satisfy the demand in the ultraviolet to visible (UV–vis) region. However, there is still a lack of perfect NLO materials for the infrared (IR) frequency conversion field owing to the stubborn performance drawbacks in commercial IR NLO crystals. − As for one outstanding IR NLO crystal, it should satisfy the following property demand: large SHG response, long IR absorption edge, high laser-damage threshold (LDT) and so forth, and thus, chalcogenides have become the preferred research system. − In comparison with critical property parameters among sulfides and selenides, selenides exhibit the greater advantages (wider infrared transmission range and larger SHG effect) for IR application; for instance, AgGaS 2 (11.4 μm and d 36 = 13.9 pm/V) versus AgGaSe 2 (18.0 μm and d 36 = 33 pm/V) and LiGaS 2 (11.6 μm and d 33 = −10.7 pm/V) versus LiGaSe 2 (13.5 μm and d 33 = −18.2 pm/V); , therefore, selenides show the better application prospect in the long-wavelength IR region (>10 μm) than sulfides.…”

Mixed-Anion-Oriented Design of LnMGa3S6O (Ln = La, Pr, and Nd; M = Ca and Sr) Nonlinear Optical Oxysulfides with Targeted Property Balance

“…Nonlinear optical (NLO) crystals, as critical devices in solid-state lasers, possess great ability to tune mature lasers to special wavelengths ranging from the deep-ultraviolet (DUV) to middle- and far-infrared (MFIR) field by a crucial frequency-conversion technique. − Many NLO oxides with wide optical bandgaps and short IR absorption (abs.) edges were widely applied in the DUV to visible region. − Unlike oxides, sulfides were mainly used for the MFIR field because of their large second harmonic generation (SHG) responses and broad IR transmission region, such as commercially available AgGaS 2 , but they suffer from harmful influences including a low laser damage threshold (LDT) and two-photon absorption from their intrinsic relatively narrow optical bandgaps. − In general, the SHG effect ( d ij ) shows an inverse relationship with the optical bandgap ( E g ) and an urgent challenge is how to balance the above two key performance parameters ( E g ≥ 3.0 eV and d ij ≥ 0.5 × AgGaS 2 ) in one material. , Recently, along with the increasing discovery of mixed-anion-based NLO compounds, such as oxyfluorides and chalcohalides, mixed-anion basic building units display a larger degree of distortion than single-anion formed groups that further show flexible regulatory ability on the material performances.…”