Physical Properties of a Promising Nonlinear Optical Crystal K₃Ba₃Li₂Al₄B₆O₂₀F

Abstract

Beryllium-free nonlinear optical (NLO) crystal K3Ba3­Li2Al4­B6O20F (KBLABF) is a newly reported promising candidate in the generation of the significant UV coherent light. A 17 × 12 × 8 mm3 bulk single crystal is successfully grown with an optimized flux molar ratio. The crystal specific heat increases from 0.65 J·g–1·°C–1 to 0.96 J·g–1·°C–1 with the increasing temperature. Meanwhile, the a-direction thermal conductivity of KBLABF is 1.11 W·m–1·K–1 at 25 °C, which is also equivalent to that of the famous NLO crystal β-BaB2O4 (1.25 W·m–1·K–1). The KBLABF crystal has moderate Vickers hardness along the a-axis and c-axis (165.1 HV0.1 and 257.7 HV0.1, respectively), which indicates it is easy to be cut and polished. Remarkably, the laser damage threshold of KBLABF is 3.32 GW·cm–2 (1064 nm, 8 ns), which even exceeds those of some famous commercial NLO crystals. This result demonstrates that KBLABF is suitable for high-power NLO applications. This work will establish the foundation for the future NLO applications of the KBLABF crystal.

K3Sr3Li2Al4B6O20F: a competitive nonlinear optical crystal for generation of a 266 nm laser

“…Owing to the high optical intensities involved in the NLO processes, one of the key indicators for judging an excellent NLO crystal device is its ability to resist laser damage. [36][37][38] The study of laser damage threshold (LDT) is a great deal for the practical application of NLO crystals. 38,39 In the present work, surface laser damage threshold studies were carried out for the K 3 Sr 3 Li 2 Al 4 B 6 O 20 F single crystals in the (001) plane with a thickness of about 1 mm.…”

“…[36][37][38] The study of laser damage threshold (LDT) is a great deal for the practical application of NLO crystals. 38,39 In the present work, surface laser damage threshold studies were carried out for the K 3 Sr 3 Li 2 Al 4 B 6 O 20 F single crystals in the (001) plane with a thickness of about 1 mm. A commercial NLO BBO wafer was also tested as the reference under the same test conditions (a laser wavelength of 1064 nm, a pulse width of 5 ns, and a laser frequency of 10 Hz).…”

Design of the Ionic Organic Nonlinear Optical Material NH4[LiC3H(CH3)O4] with Ultrawide Band Gap and Moderate Birefringence

“…By the structural analysis of the reported layered deep-UV NLO compounds, one can find that the NLO-favorable layer is commonly assembled from π-conjugated module and tetrahedral module, among which the central atom of tetrahedral module is usually Be, B, Li or Al because the bonds they form with the O atoms do not affect the band gap of crystal. There are some classic examples, such as KBBF, [5] NH 4 B 4 O 6 F, [22] LiZn(OH)CO 3 , [17a] and K 3 Ba 3 Li 2 Al 4 B 6 O 20 F. [23] Herein, guided by the above ideas, we continue to expand the study on organic flexible π-conjugated systems. By methylating the previously reported flexible NLO-active (C 3 H 2 O 4 ) 2À unit, it is anticipated that the electron-donating effect of À CH 3 can produce "σ-π hyperconjugation" interaction, thereby increasing the π-electron delocalization degree, and thus further obtaining more ideal balance between strong SHG response and moderate birefringence.…”

KLi2CO3F: a beryllium-free KBBF-type deep-UV carbonate with an enhanced interlayer interaction and large birefringence

“…These three compounds exhibit significantly enhanced SHG responses of 9, 9.5 and 10 times that of KDP, but their UV cut off edge red shifts to the UV and near-IR region. (3) Replacing tetrahedral [BeO 4 ]/[BeO 3 F] with similar [MO 4− n X n ] ( n = 1–3, X = halogen atom) units, where M atoms could be Al, Zn and B, namely K 3 Ba 3 Li 2 Al 4 B 6 O 20 F, 27 AZn 2 BO 3 X 2 (A = K, Rb, NH 4 + and Cs; X = F, Cl, Br) 28,29 and AB 4 O 6 F (A = K, Rb, and Cs, and a mixed cation between two of them). 30 Most of these borate KBBF analogues present a short UV cut off edge, but a few of them have a large birefringence exceeding KBBF, which limits their short SHG phase-matching cutoff wavelength.…”