Accessing different higher-order modes with beam self-cleaning under simple realistic tuning of initial conditions

The initial conditions in multimode fibers pumped by ultrashort laser pulses strongly determine the following nonlinear optical interactions. In this work we firstly compare the detailed spatial mode content of simple initial conditions, transverse offset and tilt. We then show how those initial conditions can both be used to achieve beam self-cleaning into higher-order spatial modes of a model graded-index fiber, with their own slight differences and advantages. Going beyond purely spatial initial conditions, we introduce self-cleaning results using spatial chirp at the input facet, whereby the different temporal envelopes of the spatial modes allows for tuning the self-cleaning process. Our results open up investigations into higher-dimensional tuning of nonlinear processes in multimode fibers using initial conditions.