Theoretical and experimental research of supercontinuum generation in an ytterbium-doped fiber amplifier

Abstract

The theoretical research of supercontinuum (SC) generation in a fiber amplifier system has been seldom reported. For the purpose of further understanding the mechanism of SC generation in fiber amplifiers, we propose a combined numerical model of the laser rate equations and the generalized non-linear Schrödinger equation to simulate the amplification of 1060 nm picosecond pulses and their spectral broadening in an ytterbium-doped fiber amplifier. The calculation results of this model are compared with the experimental results under the same conditions and a good agreement is achieved. We find that the pulse is gain amplified initially, and then dominated by stimulated Raman scattering in the normal dispersion region. In anomalous dispersion region, modulation instability, higher-order soliton fission and soliton self-frequency shift dominates the spectral broadening. It is found numerically and experimentally that the length of the gain fiber and the 976 nm pump power are the most imperative parameters to control the output power, spectral range and flatness of the SC. The pulse width of signal pulse also plays a part in influencing SC generation. The results verify that our model is promising for analyzing the physical processes of pulse evolution and SC generation in a fiber amplifier system.

Silica-based Photonic Crystal Fiber for Supercontinuum Generation in the Anomalous Dispersion Region: Measurement and Simulation

“…Recently, there have been a number of experiments and simulations demonstrating SC generation in the AD region of PCFs [10][11][12][13][14]. Li et al reported a study on the coherency of SC spectra of a tapered fluorotel-lurite micro-structured fiber in wavelength range of 1.4 to 4 µm with pumped wavelength of 1980 nm [10].…”

“…On the other hand, the number of pulses depends on the total gain of the amplifier as well as on the input pulse width. C. Lei et al numerically investigated SC generation in a nonlinear ytterbium-doped fiber amplifier with an AD region [14]. By pumping at the wavelength of 1060 nm and an output power of 300 W, a broad SC spectrum was obtained in the wavelength range from 1000 nm-2000 nm.…”

Numerical Study on Supercontinuum Generation in an Active Highly Nonlinear Photonic Crystal Fiber With Anomalous Dispersion

“…That is, the rate-equationbased approach utilized in [9] might be no longer appropriate enough for such extremely fast nonlinear interactions in the AD regime. We note that to date only a handful of numerical or theoretical studies have been carried out on analyzing novel characteristic aspects of SCG in active fibers in the AD regime [12], [18]- [20]. In particular, Lei et al reported that SCG in a Yb-doped fiber (YDF) with AD can be modeled by combining the well-known rate equation and the nonlinear Schrödinger equation (NLSE) when excited by ps pulses [12].…”

“…We note that to date only a handful of numerical or theoretical studies have been carried out on analyzing novel characteristic aspects of SCG in active fibers in the AD regime [12], [18]- [20]. In particular, Lei et al reported that SCG in a Yb-doped fiber (YDF) with AD can be modeled by combining the well-known rate equation and the nonlinear Schrödinger equation (NLSE) when excited by ps pulses [12]. However, it remains questionable to apply the given method to the rigorous analysis of SCG in the sub-100-fs regime, because the interactions between active ions and sub-100-fs ultrafast solitons, which inevitably arise during the SCG process in the AD regime, cannot be modeled properly based on the standard rate equation method.…”

Wavelength tunable ultra-short pulses based on a flat broadband spectrum generated in a nonlinear ytterbium-doped fiber amplifier

“…However, the spectrum is not particularly flat, as it is limited by the length of the fiber and the low Raman gain coefficient, as discussed in Ref. [20].…”