  The interplay between spin and orbital angular momentum in the up-conversion
process allows us to control the macroscopic wave front of high harmonics by
manipulating the microscopic polarizations of the driving field. We demonstrate
control of orbital angular momentum in high harmonic generation from both solid
and gas phase targets using the selection rules of spin angular momentum. The
gas phase harmonics extend the control of angular momentum to
extreme-ultraviolet wavelength. We also propose a bi-color scheme to produce
spectrally separated extreme-ultraviolet radiation carrying orbital angular
momentum.
