Variable square pulse vs conventional PFN pumping of Er:YAG laser

The influence of the flashlamp pump current pulse shape on Er:YAG laser efficiency and laser rod thermal focusing was studied theoretically and experimentally. Two pulse shapes, PFN (Pulse Forming Network) and VSP (Variable Square Pulse), were considered. Theoretical modeling and experimental measurements show that the pump pulse shape itself does not have a significant influence on the Er:YAG laser efficiency or thermal focusing. Instead, the major parameter influencing Er:YAG laser efficiency and thermal focusing was found to be the overall pulse duration. For PFN pulses, rise and fall times directly define the overall pulse duration, and therefore do have influence on thermal focusing. By contrast, VSP pulse duration is defined by the externally controlled on-time of the switching transistor. For square shaped pulses, short rise and fall times do not have a direct beneficial influence on thermal lensing.

► Influence of pump pulse shape on Er:YAG laser efficiency and rod thermal focusing was studied.
► Two pulse shapes conventional PFN and VSP (Variable Square Pulse) were considered.
► Pump pulse shape does not influence the Er:YAG laser efficiency or thermal focusing.
► Pumping pulse short rise and fall times do not influence the efficiency and do not reduce thermal focusing.
► Major parameter influencing the efficiency and thermal focussing at same energies per pulse is the overall pulse duration.