Utilization of optical limiting materials to suppress the input intense laser energy is obligatory in a wide variety of applications that deploy the high–power laser sources. In this letter, we demonstrate that the optimization of borate structural units in lanthanum borate (LB) glasses through the addition of various concentrations of heavy metal oxides (HMOs) (PbO and Bi 2 O 3 ) resulting in achievement of an optimum optical threshold value. The structural changes of these glasses were analyzed by 11 B MAS–NMR and Raman spectroscopic techniques. Nonlinear optical attributes were assessed by the Z–scan technique. The enhancement of two–photon absorption coefficient and decrement in optical limiting threshold factors suggest the LB glasses containing HMOs could be beneficial for power optical limiting devices. The achieved optical limiting threshold values of 0.075 and 0.114 J/cm 2 at 70 0 and 80 0 nm, respectively, are superior compared to advanced materials such as nanoparticles, carbon nanotubes, and few–layers of MoS 2 /Polymethylmethacrylates. © 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.