Beryllium‐Free β‐Rb2Al2B2O7 as a Possible Deep‐Ultraviolet Nonlinear Optical Material Replacement for KBe2BO3F2

A new beryllium‐free deep‐ultraviolet (DUV) nonlinear optical (NLO) material, β‐Rb₂Al₂B₂O₇ (β‐RABO), has been synthesized and characterized. The chiral nonpolar acentric material shows second‐harmonic generation (SHG) activity at both 1064 and 532 nm with efficiencies of 2×KH₂PO₄ and 0.4×β‐BaB₂O₄, respectively, and exhibits a short absorption edge below 200 nm. β‐Rb₂Al₂B₂O₇ has a three‐dimensional structure of corner‐shared Al(BO₃)₃O polyhedra. The discovery of β‐RABO shows that through careful synthesis and characterization, replacement of KBe₂BO₃F₂ (KBBF) by a Be‐free DUV NLO material is possible.     

Chiral Side Groups Trigger Second Harmonic Generation Activity in 3D Octupolar Bipyrimidine‐Based Organic Liquid Crystals

The design of efficient noncentrosymmetric materials remains the ultimate goal in the field of organic second‐order nonlinear optics. Unlike inorganic crystals currently used in second‐order nonlinear optical applications, organic materials are an attractive alternative owing to their fast electro‐optical response and processability, but their alignment into noncentrosymmetric film remains challenging. Here, symmetry breaking by judicious functionalization of 3D organic octupoles allows the emergence of multifunctional liquid crystalline chromophores which can easily be processed into large, flexible, thin, and self‐oriented films with second harmonic generation responses competitive to the prototypical inorganic KH₂PO₄ crystals. The liquid‐crystalline nature of these chiral organic films also permits the modulation of the nonlinear optical properties owing to the sensitivity of the supramolecular organization to temperature, leading to the development of tunable macroscopic materials.