29 W Diffraction Limited Monolithic Ytterbium Doped Fiber Laser System Operating at 976 nm in the Continuous Wave Regime

High-power diffraction limited sources emitting around 976 nm have many applications. To cite a few, several tens of watts at 976 nm laser is an outstanding source for high-brightness pumping of Yb-doped solid-state lasers [1]. In another context, 976 nm lasers when efficiently frequency doubled to 488 nm can easily be exploited in biomedical and biological applications. To these aims, the development of high-power robust and compact high power laser systems is of paramount importance, as no simple systems exist today such as laser diodes for instance. For this reason, we conduct, since several years, intense research aiming at maturating a laser technology based on monolithic flexible Yb-doped fibers specifically designed to operate at 976 nm. However, achieving efficient lasing in Yb-doped fiber at 976 nm is very challenging due to the 3-level laser configuration from which the competing emissions at 976 nm and 1030 nm have to be managed efficiently to prevent amplification at the latter wavelength. The highest power at 976 nm reported so far from a fiber laser system is 94 W [2-3] and was achieved using a Rod-type fiber. However, the rigidity of this fiber as well as its microstructured architecture doesn't allow a monolithic and compact integration. Currently, the highest power at 976 nm reported for a monolithic flexible Yb-doped fiber laser is 10.6 W [4]. In this contribution we will present a 29 W monolithic flexible fiber Master Oscillator Power Amplifier (MOPA) operating at 976 nm. The MOPA is based on a large mode area specialty fiber. The opto-geometric characteristics of this fiber allow an efficient emission at 976 nm (high core to clad area ratio) and high power level pump coupling.