The effect of 0D vacancy defects on the structural, electronic, magnetic, and optical properties of dynamically stable hexagonal boron arsenide monolayer was comprehensively studied using first-principles calculations. Five configurations of 0D vacancy defects - single boron vacancy, double boron vacancy, single arsenic vacancy, double arsenic vacancy, and single boron-single arsenic vacancy, were considered. Our density functional theory calculations indicated that arsenic vacancy induced magnetism (1.0 μB in the boron atoms around the vacancy site, whereas induced magnetism was absent for other vacancy defects. The magnitude of the induced magnetic moment for arsenic vacancy decreased with the increasing concentration of vacancy. Semiconductor to metal transition was noticed due to the introduction of single boron vacancy, double boron vacancy and double arsenic vacancy. Single boron-arsenic vacancy decreased the pristine band gap though finite band gap remained. Instigating 0D vacancy modified the optical absorption spectra of the monolayer. Work function calculations revealed that the work function increased after vacancy defect was introduced. This work will be beneficial to ascertain the multifunctionality of the defective boron arsenide monolayer as 2D nanomaterials for optoelectronic and spintronic applications.

Tunable surface plasmon resonance-based graphene nanoribbon (GNR) terahertz (THz) polarizers with adjustable operating frequency are proposed in this work. While conventional THz polarizers lack robustness and tunability, recently reported graphene-based metastructure polarizers have complex fabrication processes and comparatively smaller extinction ratios (ERs). A comprehensive study using finite-difference time-domain (FDTD) simulation technique reveals high ER, broad tunability, near-perfect degree of polarization (DOP), and low insertion loss for our proposed single and double stage GNR polarizers. The operating frequency of these narrow band polarizers can be tuned by varying GNR width, GNR pitch, chemical potential, and substrate material. Our optimized THz polarizer has an ER of 30 dB which is comparable to the commercially available THz polarizers. The maximum insertion losses within the tunable frequency range were found to be 0.24 dB and 1.87 dB for single and double stage GNR polarizers, respectively, which are substantially low. We compared the performance of the proposed structures with recently demonstrated graphene-based metastructure polarizers. The polarizers are promising for the design of photonic devices, integrated photonic circuits, and optoelectronic systems.