NH₄Be₂BO₃F₂ and γ‐Be₂BO₃F: Overcoming the Layering Habit in KBe₂BO₃F₂ for the Next‐Generation Deep‐Ultraviolet Nonlinear Optical Materials

Abstract

KBe BO F (KBBF) is still the only practically usable crystal that can generate deep-ultraviolet (DUV) coherent light by direct second harmonic generation (SHG). However, applications are hindered by layering, leading to difficulty in the growth of thick crystals and compromised mechanical integrity. Despite efforts, it is still a great challenge to discover new nonlinear optical (NLO) materials that overcome the layering while keeping the DUV SHG available. Now, two new DUV NLO beryllium borates have been successfully designed and synthesized, NH Be BO F (ABBF) and γ-Be BO F (γ-BBF), which not only overcome the layering but also can be used as next-generation DUV NLO materials with the shortest type I phase-matching second-harmonic wavelength down to 173.9 nm and 146 nm, respectively. Significantly, γ-BBF is superior to KBBF in all metrics and would be the most outstanding DUV NLO crystal.

Syntheses, characterization, and theoretical calculation of Rb2Mg3(P2O7)2 polymorphs with deep-ultraviolet cutoff edges

“…With several years of sustained exploration and research, many borates with novel crystal structures or excellent optical properties have been reported. Notable examples include a variety of beryllium borates, such as KBe 2 BO 3 F 2 (KBBF) [2], NH 4 -Be 2 BO 3 F 2 [17], NaSr 3 Be 3 B 3 O 9 F 4 [18], and some berylliumfree borates, such as K 3 B 6 O 10 Cl [19], Ba 4 B 11 O 20 F [20], and A 3 B 3 Li 2 M 4 B 6 O 20 F (A=K, Rb; B=Ba, Sr; M=Al, Ga) [21][22][23][24][25]. Beyond borates, phosphates seem to be a good material system to synthesize the deep-UV NLO materials owing to their short UV cut-off edges, as evidenced by a number of phosphates, such as BaPO 3 Cl (180 nm) [26], Ba 5 P 6 O 20 (167 nm) [27], and LiCs 2 PO 4 (147 nm) [28,29].…”

A Facile Route to Nonlinear Optical Materials: Three‐Site Aliovalent Substitution Involving One Cation and Two Anions

“…Our studies propose that three-site aliovalent substitution is af acile route for the discovery of good NLO materials.Noncentrosymmetric (NCS) oxide materials have extensively excited academic interest owing to their probable properties with applications in second-order nonlinear optics (NLO) as well as in pyroelectrics,f erroelectrics,a nd piezoelectrics. [1][2][3][4][5][6] To the best of our knowledge,a ne xcellent second-order NLO material should feature al arge second harmonic generation (SHG) coefficient, ahigh relevant laserinduced damage threshold (LDT), appropriate optical transmittance range,m oderate birefringence for achieving phase matching,and good thermal stability.Inaddition, it should be free of moisture and accessible by af acile synthetic method. [7][8][9] Metal iodates currently attract extensive research interest due to their potential outstanding SHG response.…”

(NH4)Bi2(IO3)2F5: An Unusual Ammonium‐Containing Metal Iodate Fluoride Showing Strong Second Harmonic Generation Response and Thermochromic Behavior

“…To demonstrate whether the N−H⋅⋅⋅F hydrogen bonds could reduce the growth temperature in this system, we conducted a series of experiments to elucidate the relationship between different kinds of cations and the growth temperature (see Table S5). The results revealed that the growth temperature of the ABIF crystal was 60 °C lower than that of ABi 2 (IO 3 ) 2 F 5 (A=K, Rb, Cs) regardless of the yields, which indicated that hydrogen bonds in ABIF could reduce the growth temperature in this system …”

“…Since NH 4 + possesses a similar ionic radius to K + , it also can be used as an alternative group to alkali ions in situ. Unlike alkali metals, NH 4 + and F − can form strong hydrogen bonds, which are favorable for the physical properties of the crystals and may reduce the growth temperature in this system …”