<p>This study employed focused nanosecond pulsed laser-induced nucleation to regulate nucleation and solidification at varying undercooling temperatures, creating coupled growth regions with distinct energy differences at grain boundaries. These differences promote phase separation and, under pulsed laser irradiation, lead to the accumulation of defects such as Frenkel defects and oxygen vacancies at the phase interface. This accelerates material transfer and interface migration, enhancing coupled zone growth and causing YAG and Al₂O₃ grain coarsening, which significantly alters the microstructure. At 1300°C, the Al₂O₃/YAG Eutectic Ceramic Sample 1 (AYec-01), induced by pulsed laser nucleation, showed a 10% increase in toughness compared to the Al₂O₃/YAG Eutectic Ceramic Sample 2 (AYec-02), induced by non-pulsed laser. Additionally, the mechanical property differences between samples treated at 1300°C and 1600°C underline the pivotal role of undercooling temperature in nucleation efficiency. The Al₂O₃/YAG Eutectic Ceramic Sample 1, with its fine eutectic coupled structure and crack toughening mechanism, exhibited the highest toughness. Focused nanosecond pulsed laser-induced nucleation effectively enhanced the mechanical properties of Al₂O₃/YAG eutectic ceramics, demonstrating strong potential for engineering applications.</p>