Abstract
To date highest external diffraction efficiency and two-beam coupling gain at moderate applied fields (about 30% and
260
cm
−
1
, respectively, at
60
V
∕
μ
m
) are obtained in photorefractive reflection gratings with grating periods of about
0.2
μ
m
using a standard low-glass-temperature polyvinylcarbazole based composite. Reflection gratings exhibit five times faster growth/erasure rates than conventional transmission gratings. Further, their performance is very sensitive to changes in the saturation field. This allows a reliable calculation of the photorefractive trap density,
which shows a significant enhancement with the field. Finally, the theoretical analysis
reveals the geometry-dependent competition between the birefringence and electro-optic contributions.