  A scheme for quasi-phase-matching high-harmonic generation is proposed in
which polarization beating within a hollow core birefringent waveguide
modulates the generation of harmonics. The evolution of the polarization of a
laser pulse propagating in a birefringent waveguide is calculated and is shown
to periodically modulate the harmonic generation process. The optimum
conditions for achieving quasi-phase-matching using this scheme are explored
and the growth of the harmonic intensity as a function of experimental
parameters is investigated.
