Abstract:We report an experimental realization and study of a self-Q-switched diode-pumped all-fiber Ytterbium laser. Possible mechanisms leading to establishing of self-Q-switching in the laser are discussed. Pulsed Ytterbium-doped fiber lasers operating near 1 µm are currently of increased interest as the devices potentially applicable in different areas of technology, medicine, basic research, etc. Rather than mode-locked Ytterbium fiber lasers generating ultra-short pulses (of femto-or pico-second duration), Q-switched Ytterbium fiber lasers oscillate normally pulses of nano-or submicrosecond duration ("giant pulses"). Usually the giant-pulse regimes can be realized in Ytterbium fiber lasers applying the Q-switching techniques conventional for bulk lasers, using as Q-switches acousto-or electro-optical elements, or solid-state saturable absorbers [1][2][3][4][5]. Apparently, the integrated fiber-bulk architecture of such laser schemes is a disadvantage in majority of applications. That is why implementation of Q-switched all-fiber Ytterbium lasers generating stable and powerful short pulses becomes an important point of current researches. To date, only a couple of actively Q-switched all-fiber Ytterbium laser designs have been proposed [6,7]. Meanwhile, the Q-switching arrangements in these lasers are complicate and expensive: As in all actively Q-switched lasers, additional electronic and optical circuits are needed to be incorporated in a laser scheme. So, more attention is paid now to develop passively Q-switched Ytterbium all-fiber lasers as an alternative to the actively Q-switched ones. The passive Qswitching methods to realize such lasers [8][9][10][11] have obvious potential advantages -the simplicity of implementation, low cost, and insensitivity to the environmental influences. However, there are also very few designs for passively Q-switched all-fiber Ytterbium lasers. Virtually in all these lasers the Brillouin or Raman scattering are exploited as the switching mechanisms [8][9][10]. The main drawback of the mentioned lasers is their quite instable operation that seems to stem from the stochastic nature of the Q-switching nonlinear scatterings, while giant pulses generated are quite short (nanoseconds) and powerful. An-