LaTiO₃ (H4) films were prepared using ion-beam-assisted electron beam evaporation. The effect of substrate temperature, ion-beam density, high-temperature annealing, and plasma post-treatment on the optical properties and surface topography of the H4 films were tested. Results show that increasing the substrate temperature and ion-beam density appropriately can improve the refractive index and film quality. Under 175 °C substrate temperature and 120 μA/cm² ion-beam density, the refractive index of the H4 films can reach 2.70. Moreover, annealing and plasma post-treatment can further improve the film quality. The optimized process parameters were used to prepare high reflection (HR) films with H4 for a 980-nm laser diode. The HR films with H4 exhibit the best laser damage resistance under 600 MW/cm² laser power density when compared with the HR films made with Ta₂O₅ or TiO₂ as high-index materials.