Ligand Engineering for Broadening Infrared Luminescence of Kramers Ytterbium Ions in Disordered Sesquioxides

Efficient, high-power ultrafast lasers and their Efficient, high-power ultrafast lasers and their further chirped pulse amplification (CPA) are important for modern science, which requires the laser medium with high thermal conductivity, low phonon energy, and broadband luminescence. Active ions doped sesquioxide crystals possess high thermal conductivity and low phonon energy and was considered as ideal laser media if their luminescence is broadened. However, constrained by their high melting points (>2400 degrees C), the achievement of high-quality sesquioxide crystals is a current challenge, and their spectra broadening has rarely been investigated. Here, on the basis of the successful growth of the Kramer Yb3+ ions doped novel sesquioxide LuxSc2-xO3 (0 <= x <= 2) crystals, the spectral width of the crystals can be broadened about three times by distorting the octahedral ligands. The optimized sesquioxide crystal has an ultrabroadband near-infrared luminescence, covering the wavelength range from 900 to 1200 nm. By investigating the distorted octahedral ligands and the relationship between phonon vibrations and the crystal components, we found that the local polarization and the electron-phonon coupling should be responsible for the luminescence broadening. This work presents a series of novel gain materials, which have promising applications in ultrafast lasers and CPA, and will be helpful for the design of novel materials with tailored luminescence properties.