Accurate modeling of high-repetition rate ultrashort pulse amplification in optical fibers

Abstract

A numerical model for amplification of ultrashort pulses with high repetition rates in fiber amplifiers is presented. The pulse propagation is modeled by jointly solving the steady-state rate equations and the generalized nonlinear Schrödinger equation, which allows accurate treatment of nonlinear and dispersive effects whilst considering arbitrary spatial and spectral gain dependencies. Comparison of data acquired by using the developed model and experimental results prove to be in good agreement.

Numerical Model of Chirped Pulse Amplification in Pulsed Synchronously Pumped Low-Repetition-Rate Fiber Amplifiers

“…Here, we adopted the DRE with multiple wavelength channels. In the YDF amplifier, the DRE can be expressed as [18] ( ) ( , ), ( , ) , T N N N z t z t are the total dopant number density and space-time-dependent lower and upper energy populations, respectively. h is the Planck's constant, c is the speed of light in vacuum, τ is the upper-state lifetime, z denotes the position along the fiber, t denotes the temporal coordinate, α is the background loss in the fiber, and P is the power.…”

“…The time elapsing between consecutive pump-pulses is usually greater than the lifetime of the upper level. This implies that the upper-level propagation, 2 ( ) N z , will evolve between consecutive pulses and not reach a steady-state profile [18], [19]. Therefore, our numerical model was divided into two main processes: (1) pump and (2) amplification, as shown in Fig.…”

“…The gain saturation effect can also influence the evolution of the pulse and must be included in the GNLSE. In contrast to previous studies [16], [18], in which, the gain saturation was only treated in the time domain, i.e., the used saturation energy was a constant value, the time-and wavelength-dependent gain were considered simultaneously in this study; therefore, the gain function was modified as:…”

“…To obtain the space-wavelength-dependent gain coefficient, Huang et al proposed a combined model that sequentially solves rate equations (REs) and the Ginzburg-Landau equation (GLE) while updating the inversion at each position to determine the gain along the fiber for the GLE [17]. Furthermore, Lindberg presented a model that jointly solves the REs and GNLSE [18]. It directly brings the interplay between the dispersive, nonlinear and pump-relevant effects into the model, making the gain function of the spectrum more accurate.…”

Pre-chirp managed, core-pumped nonlinear PM fiber amplifier delivering sub-100-fs and high energy (10 nJ) pulses with low noise

“…Due to the nonlinear dynamics, the operation region of PCMA can -to the best of our knowledge -only be designed numerically by solving the generalized nonlinear Schrödinger equation. To obtain accurate results, the numerical model must include the spectral gain profile of the Ytterbiumdoped fiber and other parameters of the pulse amplification, such as inversion distribution and fractional mode power of pump and signal in core [14,17].…”