Development of high-efficiency and thermally stable 793nm pump diodes for thulium laser pump applications

This paper reports on the development of high-power, high-efficiency and thermally stable 793 nm pump diodes, critical for Thulium laser systems. Single emitter chips are designed and packaged in pump modules for uncooled operation, necessitating high chip thermal stability. The 5.0 mm long devices with 220 μm contact widths demonstrate optical output power of 19 W with nearly 59% electro-optical efficiency. The optical power-drop is less than 9% over a heat-sink temperature range from 15°C to 40 °C, demonstrating crucial temperature stability required for uncooled applications. By scaling the optical power through an increased electrical contact width, the operating power is extended to 30 W while maintaining an electro-optical efficiency of approximately 55%. Furthermore, an air-cooled pump module comprising 28 laser diode chips delivers up to 400 W of optical power coupled into a 200 μm core fiber with a numerical aperture of 0.22.