Ytterbium-doped fiber laser as pulsed source of narrowband amplified spontaneous emission

Abstract

We report random noise pulsed regime of an ytterbium-doped fiber laser arranged in common Fabry-Perot configuration. We show that the laser output obeys the photon statistics inherent to narrowband amplified spontaneous emission and that the noise pulsing is properly addressed in terms of probability density and autocorrelation functions. Our novel approach reveals, in particular, that the regime’s coherence time dramatically shortens, from few ns to tens ps, with increasing laser power.

Coexistence of Quasi-CW and SBS-Boosted Self-Q-Switched Pulsing in Ytterbium-Doped Fiber Laser With Low Q-Factor Cavity

“…One of them (the upper part) corresponds to the level to which relaxation oscillations damps out into CW oscillations; it is centered approximately at a half of the mean laser power. This part may be approximated by Bose-Einstein distribution (red line) with a number of independent states of amplified spontaneous emission M = 3.7 [15], which is determined by CW optical spectrum width (24 pm, see above) and RF band of registration devices used (2.5 GHz in this case). The tail of the histogram above 4P mean can be fit with exponential decay (linear in lin-log scale, magenta line) with absolute slope lower than the slope that can be attained using Bose-Einstein distribution.…”

“…1(c)) above a pedestal of amplified spontaneous emission (ASE). This peak is well fitted with the Gaussian function with FWHM of approximately 40 pm when it is measured by OSA with 32 pm resolution at 1060 nm; after deconvolution, considering that OSA response to a narrow spectrum is Gaussian [15], the spectral width was estimated to be ~ 24 pm. At higher pump powers, the laser spectrum dramatically broadens due to spurious SC, generated in YDF and passive fiber pieces under the action of SBS pulses that get produced in the laser; see the curves labeled "Output 1" and "Output 2" in the figure.…”

“…photon noise [15], [16] described by Bose-Einstein statistics [15], [17]. However, YDFLs with low Q-factor cavities turn to kW-level random self-Q-switching (SQS), ignited by stimulated Brillouin scattering (SBS) [18]- [22].…”

Noise fiber lasers

“…It will be shown in the following sections that the FLs under study are characterized by the photon statistics described by the M -fold Bose-Einstein distribution. M -factor is the degeneracy factor that is equal to the number of independent states of amplified spontaneous emission (ASE) within the laser optical spectrum [8][9][10]:…”

“…where s is the number of orthogonal linear polarization states (1 or 2) at the photodetector input, ξ = B opt /B el is the ratio of the laser optical spectrum width (in Hz) to the RF band of the photo-receiving equipment, and erf is the Gauss error function. In turn, M -fold Bose-Einstein distribution is described as follows [8][9][10]:…”