We present a laser scanning multiphoton endomicroscope
with no distal optics or mechanical components that incorporates
a polarization-maintaining (PM) multicore optical fibre to
deliver, focus, and scan ultrashort pulsed radiation for two-photon
excited fluorescence imaging. We show theoretically that the use of
a PM multicore fibre in our experimental configuration enhances
the fluorescence excitation intensity achieved in the focal spot compared
to a non-PM optical fibre with the same geometry and con-
firm this by computer simulations based on numerical wavefront
propagation. In our experimental system, a spatial light modulator
(SLM) is utilised to program the phase of the light input to each of
the cores of the endoscope fibre such that the radiation emerging
from the distal end of the fibre interferes to provide the focused
scanning excitation beam. We demonstrate that the SLM can enable
dynamic phase correction of path-length variations across the
multicore optical fibre whilst the fibre is perturbed with an update
rate of 100 Hz.