A new technique is introduced to replace DOEs that are used for illumination in lithographic
projectors with polarization computer generated holograms (PCGHs) that produce both arbitrary
intensity and arbitrary polarization state in the illumination pupil. The additional capability of
arbitrary polarization state adds an additional degree of freedom for source-mask optimization.
The PCGHs are similar in design and construction to DOEs, but they incorporate polarizationsensitive
elements. Three experiments are described that demonstrate different configurations of
PCGHs deigned to produce a tangentially polarized ring. Measurements of ratio of polarization
and polarization orientation indicate that all three configurations performed well. Experimetns
are performed with visible (λ = 632.8nm) light.
We have constructed a high-speed image stabilization system, BESSEL, that is capable of performing
wavefront correction at a rate exceeding 1 kHz. BESSEL achieved on-sky Strehl ratios of 98-99% at 800 nm
as we approached the inner scale of atmospheric turbulence when the refractor telescope aperture was stopped
down to 25.4 mm (~r<sub>0</sub>/2). This is better than expected from Kolmogorov theory, indicating that at D ~r<sub>0</sub>/2 we
are within the inner scale of turbulence. Utilizing high Strehls and the technique of roll subtraction enabled
BESSEL to resolve the binary, ADS 10418AB, with separation of only 0.71 λ/D and a delta magnitude of ~3 mags at 800 nm. BESSEL's capability to produce high Strehls ratios means that the instrument can be used to test the performance of interference/phase coronagraphs on-sky for the first time. Integrated
with an optical vortex coronagraph, BESSEL is capable of nulling the first airy ring of Betelgeuse by more
then a factor of ten.
The optical vortex coronagraph is a promising scheme for achieving high contrast low loss imaging
of exoplanets as close as 2λ/<i>D</i> from the parent star. We describe results using a high precision
vortex lens that was fabricated using electron-beam lithography. We also report demonstrations of
the coronagraph on a telescope employing a tip-tilt corrector.