Single crystal growth and phase transition mechanism of KCsMoP₂O₉ with efficient second harmonic generation via the emerging additional periodic phase technology

Large size and high quality single crystals are the prerequisite to fully evaluate their physical properties and potential technical applications. Herein, centimeter-sized KCsMoP₂O₉ (KCMP) crystals were successfully grown using the Kyropoulos method. The value of the full width at half maximum (36′′) indicated that the grown KCMP crystals were of high quality. The type of phase transition for KCMP crystals was found to be incommensurate to prototypic transition by in situ X-ray diffraction, and the phase transition mechanism was studied using a rigid unit mode approach. In addition, the linear and nonlinear optical properties of KCMP crystals were studied, and an efficient 515 nm second harmonic laser was successfully achieved in nonbirefringent-matched KCMP crystals using the emerging additional periodic phase technology.