Numerical optimisation of a high-energy end-pumped Ho:YLF slab amplifier

Single frequency 2μm sources are useful in varied applications including remote sensing, spectroscopy and non linear conversion to the mid-infrared. However, to generate high energy pulses from a 2 μm oscillator is challenging, which is typically overcome by implementing a master oscillator power amplifier approach. The authors have previously demonstrated a single frequency Ho:YLF laser which produced up to 70 mJ per pulse at 2064nm and subsequently developed a 200W Tm:YLF slab laser to be used as pump source for a power amplifier. To design a high energy amplifier stage a numerical rate equation model was developed in MATLAB and used to determine the optimum system parameters for a Ho:YLF slab amplifier. The model was spatially and temporally resolved and based on a simplification of the travelling wave approximation, implemented so that the gain medium was discretised into three dimensions to accommodate different beam propagation factors for the pump and seed beams in both the horizontal and vertical planes of the slab amplifier.