High-quality bulk β-Ga ₂ O ₃ single crystals have been grown by optimized edge-defined film-fed growth (EFG) method.

CaGdAlO₄ (CGA) single crystals have been grown in different oxygen concentration atmospheres by the Czochralski method. Crystals grown under an oxygen-containing atmosphere presented an inconsistent brown coloration. The origin of coloration was studied by density functional theory, and the simulated results show the oxygen defects and the absorption matched well with the experimental results. The brown coloration of CGA is due to the interstitial oxygen atoms. The fundamental properties of CGA crystals with different colors, including the crystal density, hardness, thermal and optical properties, were systematically investigated and compared when taking into account the effect of color center inside. The colorless CGA was grown under an inert gas atmosphere and exhibits a wide transparency range of 227–7140 nm. The maximum phonon energy was determined to be as low as 618 cm⁻¹. The colorless CGA host crystal with a disordered structure, good thermal conductivity, low maximum phonon energy and wide transparency is promising for ultrafast ultraviolet and visible laser applications.

Herein, bulk single crystals of Er:Y₃Sc₂Ga₃O₁₂ (Er:YSGG) with a maximum diameter of 35 mm or a maximum length of 100 mm were successfully grown by the Czochralski method using a 60 mm diameter crucible. The high-resolution X-ray diffraction and optical interferometry results indicated that the as-grown crystals were of high quality. The crystalline perfection of the as-grown crystal was evaluated to be 20.58′′ via the FWHM of the rocking curve, and the optical homogeneity RMS was in the order of 10⁻⁶. A continuous wave laser of the Er:YSGG crystal operating at 2798.7 nm has been demonstrated. Moreover, a maximum output power of 745 mW has been realized. The achieved maximum slope efficiency is 31.5%, which is, to date, the highest slope efficiency in the Er:YSGG crystal lasers operating at ∼2.8 μm.