  The first scheme for quasi-phase-matching high harmonic generation of
circularly polarized radiation is proposed: optical rotation
quasi-phase-matching (ORQPM). In ORQPM propagation of the driving radiation in
a system exhibiting circular birefringence causes its plane of polarization to
rotate; by appropriately matching the period of rotation to the coherence
length it is possible to avoid destructive interference of the generated
radiation. It is shown that ORQPM is approximately 5 times more efficient than
conventional QPM, and half as efficient as true phase-matching.
