  We report trapping and propagation of photonic Dirac mode in a helically
twisted hollow core photonic crystal fiber (HC-PCF) where the trapped light in
the hollow (air) defect can preserve the orbital angular momentum (OAM). We
show that a photonic Dirac point can emerge even in a twisted system for a
suitable choice of curvilinear coordinate and the related waveguide defect
modes defined in the new basis can preserve the associated OAM during axial
translation. The effect of twist rate, defect geometry and crystal dimension on
the propagation of OAM carrying trapped Dirac modes is critically analyzed. The
results derived by FEM simulation are verified with an analytical theory based
on dynamics of Bloch modes in twisted photonic crystals which are in good
agreement. The proposed HC-PCF can play an important role in exciting and
guiding of OAM carrying modes that help particle trapping and quantum
communication.
