Low-temperature output characteristics of LD-pumped lasers via temperature-dependent rate equations

To address the significant decline in single-pulse energy of 1.5 μm LD end-pumped passively Q-switched lasers under low-temperature conditions, this study established a computational model capable of predicting laser output characteristics across varying temperatures. Numerical simulations were performed to systematically analyze low-temperature output behavior. By incorporating temperature-dependent physical mechanisms—including pump wavelength drift, reduced Yb³⁺→Er³⁺ energy transfer efficiency, prolonged Co²⁺:MgAl₂O₄ recovery time, and variations in fluorescence lifetime and emission cross-section—into rate equations, we developed temperature-dependent rate equations. Matlab simulations reveal performance degradation across the range from -40 to 60 ℃: below -10 ℃, single-pulse energy and peak power drop sharply, reaching only 28.1 μJ at -40 ℃. Pulse width broadens dramatically below 0 ℃, extending to 29.8 ns at - 40 ℃. Simulations of intracavity photon density evolution further demonstrate pulse quality deterioration and reduced pulse generation at low temperatures. This work clarifies variation patterns and key mechanisms of low-temperature performance degradation, providing a theoretical foundation for temperature compensation design in wide-temperature-range laser engineering applications.