Gravity-Field Self-Regulatory Engineering Enables PbIn₆Te₁₀ Nonlinear Optical Crystals Boosting Laser-Induced Damage Threshold

Mid- to far-infrared (MFIR) laser sources are essential for spectroscopy, remote sensing, communication, and environmental monitoring. However, scalable growth of high-quality lead indium telluride (PbIn₆Te₁₀, PIT), as a promising nonlinear optical (NLO) material for MFIR frequency conversion, has long been hindered by lead segregation. Gravity-induced accumulation of these intrinsic segregants destabilizes the growth interface, leading to heterogeneous nucleation and cracking. Herein, we develop a gravity-field self-regulatory strategy to grow crack-free PIT single crystals reaching Ø27 × 145 mm. MFIR frequency conversion devices fabricated from these crystals achieve a high nanosecond-regime laser-induced damage threshold of 24.2 MW/cm² under 7.2 µm, 17 ns pulsed irradiation, with validated second harmonic generation featuring synchronous pulse compression for generating narrower mid-infrared pulses. The enhanced performance arises from the gravity-mitigated horizontal Bridgman method, which alleviates gravity-induced interface disturbance and enables low-gradient growth to suppress lead segregation, the primary drivers of growth defects. This work provides a robust growth strategy for segregation-prone multi-component NLO crystals, paving the way for next-generation compact, high-sensitivity MFIR spectroscopic systems.