Kinetic modeling of Q-switched high-power ytterbium-doped fiber lasers

Abstract

We present a kinetic model for Q-switched, cladding-pumped, high-power Yb-doped fiber lasers that are based on the rate equation, in a difference equation form, of ion population and propagation equations for both pumping and signal light. The effects of fiber-laser parameters, such as doping, length, pump power, and repetition rate on pulse characteristics are analyzed. This model is used to analyze the performance of Q-switched multicore fiber lasers and to show the output pulses with enhanced characteristics.

Design of a Bi-Pulse Fiber Laser for Particle Image Velocimetry Applications

“…The most important observation is the presence of multiple peaks. This phenomenon has been already reported in references [5,11,12]. The separation of the neighboring peaks is actually equal to the round trip time, 47.5 ns for our 5-m fiber.…”

“…If this repetition rate is low (typically less than 1 kHz), the pulse that is calculated presents directly its steady state shape: all parameters have the time to return to their switch-off steady state value before a new modulation of the AOM occurs, and a second calculus of the pulse leads to a shape similar to the first one. If the repetition rate is higher, the calculated pulse reaches its steady-state shape only after 3, 4 or 5 periods of modulation (see discussion in reference [5]). In this case, the calculus of the pulse-shape is much longer as it requires many periods of modulation of the AOM until stabilization of the shape is observed.…”

“…The fiber laser that will be considered is based on the typical linear cavity described schematically in Fig. (1) [5]. The laser cavity consists of a laser medium (an Yb-doped double-clad fiber, noted YDF), an undoped fiber (a dispersion-shifted single-mode fiber, noted DSF) spliced on the right-hand side of the amplifying fiber [3,6], an acoustooptic modulator and two mirrors of reflectivities R 1 and R 2 .…”

“…In addition, much progress has been observed in the last decade concerning the development of high power fiber lasers, and the emission of microjoule nanosecond pulses is not a problem. Finally, the emission of multipeak pulses has been evidenced recently [5], and it seems possible to emit a pair of pulses using only one fiber laser cavity. Such a device would significantly improve the precision in PIV experiments, as the spatial alignment of the two pulses would be systematically realized.…”

Analysis of Nonlinear Effective Absorption Coefficient of Double Cladding Fiber

“…Based on those theories, plenty investigations and simulation work on continues wave (CW) [10,11] and Q-Switch [12][13][14] high power fiber laser have been conducted using numerical analysis algorithm. All those simulation and modeling work assume a constant absorption coefficient in the fiber core, and utilize confinement factor F to estimate the fraction of the pump power actually coupled to the fiber core.…”