Tunable long-wave-pass cutoff in Cr6+-doped Li2MoO4 single crystals grown by the Czochralski method

Long-wave-pass (LWP) optical filters based on single crystals offer superior thermal stability and high-power handling capability compared to conventional thin-film systems. In this work, high-quality Cr 6+ -doped Li 2 MoO 4 single crystals with varying dopant concentrations were successfully grown by the Czochralski method. Structural characterization confirms that the crystals retain a trigonal phase, with Cr ions predominantly substituting for Mo sites in the lattice in the +6 oxidation state. Optical measurements reveal that the absorption cutoff wavelength can be continuously tuned from 300 to 530 nm by adjusting the Cr 6+ concentration, while maintaining high transmittance in the long-wavelength region. First-principles calculations demonstrate that the incorporation of Cr 6+ introduces localized Cr-3d states within the bandgap, leading to effective bandgap narrowing and tunable optical response. In addition, the crystals exhibit favorable thermal conductivity and mechanical properties, supporting their suitability for high-power optical applications. These results establish Cr 6+ -doped Li 2 MoO 4 single crystals as promising candidates for thermally robust and spectrally tunable LWP optical filters.