Impact of thermal lensing on the TMI threshold powers in rod-type Yb-doped fiber amplifiers.

The impact of thermal lensing (TL) on the transverse mode instability (TMI) threshold power in rod-type fiber amplifiers is investigated. Simulations are conducted with a 3D coupled mode analysis on a set of five scaled large pitch fiber (LPF) amplifiers. The LPF fibers are represented by surrogate step-index fibers (SIFs) with scaled cladding diameters, core diameters, and numerical apertures for a fixed normalized frequency V equal to 3.

Pump RIN reduction of the TMI threshold powers in Yb-doped kW class fiber amplifiers.

A 3D spatially resolved coupled mode and perturbation analysis for the transverse mode instability threshold powers in Yb-doped fiber amplifiers is extended to include threshold power reduction induced by the pump laser relative intensity noise (RIN). A static intensity grating combines with the fluctuating pump intensity to generate an inversion standing wave. The forward component of the standing wave contributes to the nonlinear coupling between the fundamental mode and the higher-order mode (HOM), thereby reducing the threshold power.

Spacially resolved coupled mode analysis for TMI threshold powers in quantum and Rayleigh scattering limits.

A 3D spatially resolved coupled mode and perturbation analysis for the transverse mode instability (TMI) threshold powers in Yb-doped fiber amplifiers is presented in this paper. Threshold powers are computed in the quantum and thermal Rayleigh scattering limits and are compared with those calculated by other coupled mode analyses. Quantum-limited threshold powers are found to be more than three times greater than those calculated with coupled-mode analyses that use uniform and/or average gain approximations.

SBS threshold measurements and acoustic beam propagation modeling in guiding and anti-guiding single mode optical fibers.

A 4.3 dB stimulated Brillouin scattering (SBS) threshold suppression is measured in a passive Al-doped acoustically anti-guiding single mode optical fiber relative to that of a Ge-doped acoustically guiding single mode optical fiber. Stimulated scattering is generated by the electrostrictive acoustic wave generated in the fiber core.