LAUSR

Modulation of light refers to the modulation of electromagnetic radiation in the optical region including visible light as well as ultraviolet and infrared radiation, in which the amplitude (and therefore the intensity), phase, frequency or polarization of the radiated oscillations can be changed [1]. Optical modulator devices are widely used in industry, as represented by liquid crystal optical modulators having an annual global market worth of over US$100 billion. Currently, optical modulators working in the visible and infrared regions aremature, while those that can work in the deep ultraviolet (UV) region are rare. It is difficult for existing technologies like organic liquid crystal optical modulators to modulate deep UV light because they use organicmolecules as activematerials,which absorb UV heavily and/or are not stable under high energetic deep UV photons. On the other hand, inorganic birefringent crystals can modulate deep UV light while it has fixed birefringence after fabrication and cannot be tuned by an external field [2].Therefore, the community still lacks a technology that can stably and continuously tune deep UV light in a transmissive manner. Recently, joint research [3] led by Bilu Liu of Tsinghua University, and Hui-Ming Cheng and Baofu Ding of the Chinese Academy of Sciences, involved the fabrication of a stable and magnetictunable deep UV light modulator using two-dimensional (2D) hexagonal boron nitride (h-BN) based inorganic liquid crystals, addressing the lack of transmissive light modulators in this deep UV region. The authors first produced 2D h-BN flakes via a top-down exfoliation technique; these have an average flake size and thickness of 477 nm and 7.5 nm, respectively. The h-BN flakes, dispersed in aqueous solution, behave as inorganic liquid crystals. The 2D h-BN has a large optical bandgap of ∼6 eV, guaranteeing its high transparency at short wavelengths, i.e. >70% transmittance at a wavelength of 266 nm. In addition, the 2D h-BN flakes are found to show anisotropicmagnetismwith the in-plane easy axis and the out-of-plane hard axis, that is, the alignment of h-BN flakes in dispersion can be tuned by an external magnetic field. Such