Amplified spontaneous emission (ASE) effect on gain and stored energy

Farrès P. Mattar

L. Allen

Tao Wei Tao Wei, Jianfeng Li Jianfeng Li, Jianhua Zhu Jianhua Zhu

Some analysis of the transient response of the Yb-doped fiber amplifier are performed by solving a set of time-dependent rate and power transfer equations based on finite-difference method. Meanwhile, the variation of time to reach the steady state for upper level population distribution, the forward and backward amplified spontaneous emissions (ASEs) and stored energy on the system parameters including pump power, fiber length, Yb-doped concentration, and core area are numerically simulated, respectively. The results show that, by optimizing pump pulse width, stored energy can reach or even exceed the steady state value of continuous wave (CW) pump. By increasing Yb-doped concentration and core area, stored energy is increased, the ASE is suppressed and the ASE built-up time is postponed. In addition, the experimental results show the validity of the theoretical ASE built-up time. The obtained results can provide important guiding for the optimization of pump pulse width and fiber parameters.

Chana Goren, Y. Tzuk, Gilad Marcus +1 more

Amplified spontaneous emission (ASE) occurs in media with large gain, and affects both the magnitude and the spatial distribution of the inversion. In this work we theoretically study the effect of ASE in three-dimensional, rectangular slab amplifiers, using Monte Carlo type computer simulations. We found that in one-dimensional amplifiers ASE is always larger at the edges so that the inversion has a maxima at the center of the amplifier. However, in two- and three-dimensional amplifiers, the inversion has a minimum at the center of the amplifier for low gain, and a maximum at the center of the amplifier for high gain. Thus, the inversion profile can be changed by increasing the gain from a minimum at the center, through a plateau, to a maximum at the center. A simple analytical theory was developed and agrees with these results.

C. R. Willis

M. Andia, Étienne Wodey, F. Biraben +2 more

We have developed a laser source generated by frequency doubling of a seed laser at 1560 nm using a periodically poled lithium niobate crystal. The seed laser passes through a 30 W fiber amplifier. The laser source at 780 nm is used to perform Bloch oscillations of ultra-cold atoms in an optical lattice. In this paper we investigate the decoherence effects induced by the amplified spontaneous emission (ASE) in the gain medium. We show that the ASE drastically reduces the efficiency of Bloch oscillations. We totally filter out the ASE around the D2 line using a heated rubidium vapor cell. We precisely determine the power spectral density of the ASE by measuring the fraction of atoms transferred from the hyperfine level F=1 to F=2, when the laser is switched on.