Uniformity of pump intensity distribution in diode-array side-pumped laser rod

Abstract

Diode-pumped solid-state lasers are high efficiency, long lifetime, compact and reliable, so they have been covering a wide range of applications. Thermal effect is a major limiting factor in scaling the average power of high-power solid-state lasers, so it is a critical issue in designing diode-pumped solid-state lasers. The uniform pump intensity distribution in laser rod can weaken the influence of thermal effects in laser, and the research of improving the pump distribution uniformity has attracted a great deal of attention. People usually establish a model of single diode-bar pumped laser rod to calculate the distribution. However, for diode-array pumped high-power lasers, the model is limited and has deviation with the actual pump distribution, which cannot reflect the real working conditions in the laser. In this paper, the theoretical model of diode-array pumped laser rod is built. Based on the actual working environment of diode-array side-pumped Tm:YAG laser rod, the expression of pump intensity distribution in the laser medium is deduced. Additionally, the influence of total pump power, pump structure, Tm:YAG rod characteristic parameters and pump beam radius on pump intensity distribution are simulated and analyzed. Moreover, the parameters are optimized in order to obtain the optimistic results which are efficient to improve the uniformity of pump distribution. The results show that when the pumping distance from diode-array to the rod's surface is 3mm, the distance between two rows of diode-bars is 1mm, the absorption coefficient is 330m -1 ,the pump beam width is 2.5mm,the pump intensity distribution of five-way pumped laser rod is improved, and then the thermal effects could be weakened. The presented results can provide theoretical guidance to design and optimization of high-power lasers. INTRODUCTIONDiode side-pumped solid state lasers are covering a wide range of applications due to their high efficiency, long lifetime and high reliability. As a core component of the laser system, laser rod may compromise the system's performance because of the thermal effects induced by the coactions of pump radiation and surface cooling required for heat extraction within laser working medium [1][2][3] . Therefore thermal effects in laser rods are gaining importance as a critical issue in designing and optimizing of the diode side-pumped solid state lasers [4,5] . The uniform pump intensity distribution in laser rod can weaken the influences of thermal effects in laser [6] , and studies relating to improving the pump distribution uniformity have received a great deal of attention. A single-line diode-pumped model [9,10] is usually assumed to calculate the pump intensity distribution. However, for diode-array pumped high-power lasers, the model is limited and has deviation with the actual pump distribution, which cannot reflect the real working conditions in the laser. [11] . In this paper, we established a thermal analysis model of double-line LDA pumped laser rod. In instance, taking the Tm:YAG as the workin...