Spectral property optimization for a narrow-band-filtered superfluorescent fiber source

Abstract

The spectral broadening properties of a narrow-band-filtered superfluorescent fiber source (SFS) with different spectral shapes and spectral widths are analyzed numerically for the first time. Similar to other types of incoherent light, it is revealed that there exists a spectral broadening saturation phenomenon for the narrow-band-filtered SFS, and the output spectral width plus the stimulated Raman scattering effect could be reduced through using an active fiber with a higher group-velocity dispersion coefficient. Besides, both the spectral shapes and spectral widths have a significant effect on the spectral broadening property and the stimulated Raman scattering threshold of the narrow-band-filtered stimulated Raman scattering, and the filtered SFS with narrower spectral width will broaden faster during amplification. The results help to optimize the spectral properties of the filtered SFS to obtain a narrower spectral width at a specified output power.

2-kW-level superfluorescent fiber source with flexible wavelength and linewidth tunable characteristics

“…While the central wavelength at the long-wavelength side keeps almost unchanged compared with the pre-amplifier. By optimizing the operating temperature and the system parameters such as fiber length in the seed and amplifiers [31,32,35], it's possible to further suppress the ASE light, reduce the wavelength variation and increase the wavelength tunable range.…”

“…As presented in Figure 4(c), the FWHM linewidth is tunable over 2.5-9.7 nm. However, it is seen that the spectra after the main amplifier are symmetrical and have long tails, so the FWHM linewidth cannot fully describe the spectral evolution; here, we introduce another parameter, the root-mean-square (RMS) linewidth, to further analyze the spectral broadening [35] . Figure 4(d) presents the broadening factors of the RMS linewidth as functions of the output power.…”

“…To further investigate the generation and amplification of the wavelength and linewidth tunable SFS, especially for establishing the role of gain competition and nonlinear effects, a numerical simulation is conducted based on the combining of rate equations and the GNLSE (see Refs. [35][36][37] for details):…”

“…Equation (2) describes the evolution of the pump power P p with the fiber length, where is the overlap factor, σ a and σ e represent the absorption and emission cross-sections, respectively, N 0 is the dopant concentration, N 2 denotes the number of excited Yb ions, which is governed by Equation (3), τ is the lifespan of the excited state population, is the reduced Planck constant, and A is the doped cross-section area. The active gain is given by Equation ( 4), which acts as a bridge between the rate equations and the GNLSE [35,36] . The SEN is approximated by a Gaussian random process with zero mean value, which satisfies [35]…”

“…The active gain is given by Equation ( 4), which acts as a bridge between the rate equations and the GNLSE [35,36] . The SEN is approximated by a Gaussian random process with zero mean value, which satisfies [35]…”