Realization of a compact 10-W 976-nm ytterbium-doped all-fiber laser.

We have demonstrated a compact and cost-effective ytterbium-doped all-fiber laser operating at 976 nm. By utilizing a commercially available ytterbium-doped fiber with a length of only 18 cm, we achieved a lasing power of 10.3 W, with a slope efficiency of 25.4%. To our knowledge, our work presents the shortest gain fiber ever documented in the literature capable of delivering tens-of-watt 976-nm lasing power. The design is compatible with conventional fiber components, simplifying the monolithic assembly process. Notably, the incorporation of such a short gain fiber obviated the need for additional measures to suppress the strong 1.03-µm emission.

Simulation for efficiency improvement of a thuilium Q-switched ytterbium-doped all-fiber laser.

We theoretically explore the mechanism in a thulium Q-switched ytterbium-doped all-fiber fiber laser using a set of rate equations to model the correlations between the photons and the five energy levels of thulium involved in the Q switching mechanism. We demonstrate that by coupling with a gain-switched resonator, the Q-switched laser is stabilized up to the maximum pulsing rate that is limited by the lifetime of level 3H5. To the best of our knowledge, this is the first study that revealed that level 3H5 plays an essential role in reinitialization, achieving sequential pulses, and limiting the maximum repetition rate.

Minimization of Fresnel reflection by anti-reflection fiber Bragg grating inscribed at the fiber ends.

In this paper, we proposed and numerically demonstrated a novel method to effectively minimize Fresnel reflection from a perpendicularly cleaved fiber using a uniform fiber Bragg grating (FBG) inscribed at the fiber end. By matching the reflectivity of an in-line FBG with the reflectivity caused by the glass-air boundary, the FBG acts as a virtual boundary, which provides destructive interference and suppresses Fresnel reflection. We achieved an anti-reflection FBG with a return loss of more than 80 dB by ensuring that the product of the index contrast and grating period number is almost constant, with a value of 0.2695.

Lensless intracavity focusing in a passively Q-switched all-fiber laser using the mode-field-area mismatch.

Intense lensless intracavity focusing in a saturable absorber Q-switched all-fiber laser resonator by use of loss arrangement and mode-field-area mismatch between the fibers is investigated for the first time. The intracavity power distribution was related to the locations and values of the cavity losses as the saturable absorption loss, the reflection loss of the output coupler, and the splicing loss between the gain fiber and the absorber fiber. With a mode-field-area mismatch and a reduced splicing loss with the gain fiber, a power density in the absorber fiber was achieved that was 11.9 times higher than that in the gain fiber.

All-fiber passively Q-switched erbium laser using mismatch of mode field areas and a saturable-amplifier pump switch.

We propose and demonstrate an all-fiber self-Q-switched erbium laser system that is saturable-absorber Q switched by the mismatch of the mode-field areas in the resonator and stabilized with a saturable-amplifier pump switch. Sequential pulses with a pulse energy of 8-6 microJ and a pulse duration of 80-320 ns, corresponding to a pulse repetition rate of 0.25-1 kHz, were obtained using a cw 980 nm laser-diode pump. A peak pulse power of near 100 W was achieved.