Highly efficient, variable pulse format, 770 nmsourcebased on powerful seeded fibre amplifier andsecond-harmonic generation in periodically poled KTP

Abstract
A 770 nm source with variable (50 ps to 2 ns) pulse duration and repetition rates up to 25 MHz is demonstrated using seeded Yb/Er amplifier and second-harmonic generation in periodically poled potassium titanyl phosphate (KTP). A 44% peak power conversion efficiency is achieved. Scalability of the results to the nonlinear conversion with watts of average output power is feasible.