Frequency modulation to amplitude modulation conversion of different broadband pulses propagating in Nd-glass amplifiers

During propagating in Nd-glass amplifiers, the spectra of the broadband laser pulses are modulated due to gain narrowing and gain saturation effects, resulting in loss of sidebands and unbalance of the spectra, and further leading to the temporal intensity modulation. The amplitude modulations (AMs) have been numerically simulated for different broadband laser sources. The effects of the gain bandwidth, the laser bandwidth, as well as the deviation of central wavelength between the laser source and amplifier on the AMs have been analyzed. Results indicate that all of the different broadband laser sources discussed in this paper exhibit more or less AMs, and the temporal intensity modulation of stacked chirped pulses is smaller than that of sinusoidally frequency-modulated pulses.