In situ femtosecond laser processing system for high-temperature molecular beam epitaxy under ultrahigh vacuum

Femtosecond laser processing (FLP) enables high-precision, non-contact material modification and is promising for in situ control during thin-film growth. However, integrating FLP into molecular beam epitaxy (MBE) systems is challenging due to ultrahigh vacuum, elevated temperatures, and limited chamber space. This work reports the development of an FLP system compatible with MBE environments. The optical layout, mechanical structure, and thermal design were optimized to address spatial and thermal constraints. A structural thermal optical performance simulation was performed using COMSOL to verify stable operation under coupled multiphysics conditions. The system was experimentally validated to operate stably at 750 °C and ${10}^{-8}$ Pa, achieving a processing accuracy with an average error of 0.214 %, providing an effective approach to the in situ control of grown film materials.