Deep‐Ultraviolet Nonlinear‐Optical van‐der‐Waals Beryllium Borates**

Abstract

Van-der-Waals (vdW) deep-ultraviolet (DUV) nonlinear-optical (NLO) materials hold great potential to extend DUV NLO applications to two dimensions,but they are rare in nature.I nt his study,w ep ropose ad esign principle to realize vdW DUV NLO materials via structural evolution from the non-vdW (BO 3 )-(BeO 3 F) layers in KBe 2 BO 3 F 2 (KBBF) to the vdW (BO 3 )-(BeO 4 H) layers in berborite Be 2 BO 5 H 3 (BBH) and the vdW (BO 4 )-(BeO 4 )l ayers in beryllium metaborate BeB 2 O 4 (BEBO). Based on first-principles calculations,t he fundamental NLO properties of BBH and BEBO demonstrate that ab alanced DUV NLO performance can be achieved in these two systems.I mportantly,B BH, al ayered material existing in nature,c an achieve an available DUV phasematched output with strong second harmonic generation (SHG) for 177.3/193.7 nm DUV lasers,w hich is almost identical to that of KBBF.R emarkably,B EBO shows an excellent DUV SHG capacity and an even shorter phasematching wavelength than KBBF.T herefore,t he newly discovered vdW BBH and BEBO,o nce verified by experiments,c ould provide an ideal platform to study DUV NLO effects in three dimensions and two dimensions.

Review of Heteroleptic Tetrahedra as Birefringent or Nonlinear Optical Motifs

“…The third section involves heteroleptic tetrahedra POS­(NH 2 ) 2 , PO 2 S­(NH 2 ), GeO 3 (NH 2 ), GeS 3 (OH), and GeS 2 (OH) 2 , and they all demonstrate wide HOMO-LUMO energy gaps. It has been suggested that utilization of the monomers OH in hydroxyborates , and NH 2 (anisotropic tetrahedron SO 3 (NH 2 ) in M­(NH 2 SO 3 ) 2 (M = Sr, Ba)) is beneficial to the blue shift of the band gaps. Compounds containing the five heteroleptic tetrahedra are NH 4 POS­(NH 2 ) 2 , (NH 4 ) 2 PO 2 S­(NH 2 ), K 3 GeO 3 (NH 2 ), K 3 (H 2 O)­GeS 3 (OH), and Na 2 GeS 2 (OH) 2 (H 2 O) 5 .…”

Hydroxyfluorooxoborate Na[B3O3F2(OH)2]⋅[B(OH)3]: Optimizing the Optical Anisotropy with Heteroanionic Units for Deep Ultraviolet Birefringent Crystals

“…Theh ydrogen and/or fluorine in [B 3 O 3 F 2 (OH) 2 ]a nd [B(OH) 3 ]u nits make all the planar moieties to parallel extending the (011) plane.T he hydrogen-bonding interaction is acrucial factor defining the unique structure and property,w hich has also been verified in some previous literatures. [13] More importantly,N a-centered polyhedra act as linkers and pillar-like roles in layers and interlayers,r espectively.I nt he coordination sphere of Na atoms,t hree equatorial Oa toms come from one [B(OH) 3 ] and two [B 3 O 3 F 2 (OH) 2 ]u nits and residual Fa toms in equatorial position belong to the same [B 3 O 3 F 2 (OH) 2 ]u nit (Figure 1e). As for two polar Fatoms,their relative benzenelike [B 3 O 3 F 2 (OH) 2 ]u nits locate in different layers;t hese antiparallel pseudo layers (regarded as Aa nd A')f urther pack and finally form a-AA'AA'-packing mode (Figure 1f).…”

Deep-ultraviolet nonlinear optical crystals: concept development and materials discovery

“…Furthermore, another design strategy to eliminate the A-site cations, i.e., via van der Waals (vdW) connection, has been proposed, and a series of possible DUV NLO structures have been accordingly predicted 68 , 73 , 75 , 78 , 81 . Among them, an existing berborite (Be 2 BO 5 H 3 , BBH) mineral as shown in Fig.…”

“…Among them, an existing berborite (Be 2 BO 5 H 3 , BBH) mineral as shown in Fig. 2h can theoretically achieve DUV NLO performance comparable to KBBF 73 . The vdW DUV NLO crystal, firstly proposed by our group, holds great potential to extend the DUV NLO applications with higher output power and shorter output wavelength.…”