Fundamentals of direct multi-wavelength diode pumping of Ti:Sapphire lasers for enhanced optical-to-optical conversion efficiency across a broad spectral range

Abstract

Direct-diode-pumped titanium–sapphire lasers are gaining popularity as sources of coherent light due to their wide emission bandwidth, cost-effectiveness, ergonomics and compactness. Despite recent advances in this field, reported laser output powers remain relatively low. Here, we present a theoretically and experimentally described pumping technique that involves the spectral and collinear combination of blue and green laser diode radiation. We show that this approach yields an impressive average optical-to-optical efficiency of 16.6 % in continuous-wave laser mode and up to 43.6 % in femtosecond mode based on Kerr-lens mode-locking. Consequently, with a maximum pump power of 15 W, the generated output power at 770 nm reaches 2.5 W in continuous-wave mode. With a pump of 14.5 W we have 1.84 W in femtosecond mode. In the future, such titanium–sapphire lasers promise to become even more accessible and user-friendly.