Optimal Photon Energy Transfer on Titanium Targets for Laser Thrusters

Using two infrared pulsed lasers systems: a picosecond solid-state Nd:YAG laser with tunable repetition rate (400 kHz - 1MHz) working in a burst mode of multi-pulse train and a femtosecond Ti:Sapphire laser amplifier with tunable pulse duration inthe range of tens of femtoseconds up to tens of picoseconds, working in single-shot mode (TEWALASS facility from CETAL-NILPRP), we have investigated the optimal laser parameters for kinetic energy transfer to a titanium target for laser-thrustapplications. In the single-pulse regime, we controlled the power density by changing both duration and pulse energy. Inthe multi-pulse regime, the train’s number of pulses (burst length), and the pulse energy variation were investigated. Heatpropagation and photon reflection-based models were used to simulate obtained experimental results. In the single-pulseregime, optimal kinetic energy transfer was obtained for power densities of about 500 times the ablation threshold correspondingto the specific laser pulse duration. In multi-pulse regimes, the optimal number of pulses per train increases with the trainfrequency and decreases with the pulse power density. An ideal energy transfer efficiency resulting from our experiments andsimulations is close to around 0.02%.