  Among Super-Mirror (SM) polarizers, solid-state devices have many advantages.
The most relevant is 5-10 times smaller length compared to air-gap polarizers
allowing to apply stronger magnetic fields. An important condition for a good
SM polarizer is the matching of the substrate SLD (Scattering Length Density)
with the SM coating SLD for spin-down neutrons. For traditional Fe/Si SM on Si
substrate, this SLD step is positive when a neutron goes from the substrate to
the SM, which leads to a significant loss of the polarizer performance at small
Q. Instead, we use single-crystal Sapphire/Quartz substrates. The latter show a
negative SLD step for spin-down neutrons at the interface with Fe and,
therefore, avoid the total reflection regime at small Q. To optimize the
polarizer performance, we formulate the concept of Sapphire V-bender, perform
ray-tracing simulations of Sapphire V-bender, compare results with those for
traditional C-bender on Si, and study experimentally V-bender prototypes with
different substrates. Our results show that the choice of substrate material,
polarizer geometry and the strength and quality of magnetizing field have
dramatic effect. In particular, we compare the performance of polarizer for the
applied magnetic field strength of $50 mT$ and $300 mT$. Only the large field
strength provides an excellent agreement between the simulated and measured
polarization values. For the double-collision configuration, a record
polarization $>0.999$ was obtained in the neutron wavelength band of $0.3-1.2
nm$ with only $1\%$ decrease at $2 nm$. Without any collimation, the
polarization averaged over the full outgoing capture spectrum, $0.997$, was
found to be equal to the value obtained previously only using a double
polarizer in the "crossed" (X-SM) geometry. These results are applied in a
full-scale polarizer for the PF1B instrument.
