Abstract
The nonlinear waveguide equation is studied quasi-analytically for insights
into the effect of waveguide designs. Equations governing stationary mode
and transient process are successfully derived. A number of new understandings
of the nonlinear process at high peak power in optical waveguides are developed
which will be critical for fiber laser research and developments at extremely
high peak powers. The first key finding is that the critical power for nonlinear
self-focus is independent of waveguide parameters. The second key finding
is that the nonlinear guided stationary mode is a stable solution of a nonlinear
waveguide below the critical power for nonlinear self-focus and has a reduced
mode size dependent on the optical power and $V$ value of the waveguide. The third key finding is
that the transient process scale with Rayleigh range similar to those in bulk
media and are adiabatic, i.e., the optical power remains in the fundamental
mode. The fourth key finding is that a larger $V$ value increases the transient process and self-focus
distance, and the self-focus distance is proportional to square root of the
optical power and independent of $V$ value at higher power levels, i.e., it becomes more like a bulk
medium at peak powers above ten times critical power levels. B integrals are
calculated for various amplifiers, taking into account the impact of the gradual
collapse of beam size along the amplifier.
© 2008 IEEE
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