Linear Tuning of Phase-Matching Temperature in LiNbO₃:Zr Crystals by MgO Co-Doping

We grew a series of co-doped LiNbO₃ crystals with fixed 1.5 mol % ZrO₂ and various MgO concentrations (1.0, 3.0, 4.0, 6.0 mol %), and investigated their optical properties and defect structures. By 3.0 mol % MgO co-doping, the optical damage resistance at 532 nm reached 6.5 × 10⁶ W/cm², while the phase-matching temperature for doubling 1064 nm was only 29.3 °C-close to room temperature-which was conducive to realizing the 90° phase matching at room temperature by slightly modulating the incident angle of the fundamental beam. Notably, we found that the phase-matching temperature increased linearly with the increase of MgO doping, and this linear dependence helped us to grow the high-quality crystal for room temperature 90° phase matching. Moreover, the defect analysis indicated that the linear tuning of phase-matching temperature might be attributed to Mg Li + + Zr Nb - neutral pairs in crystals.