  In recent years, in looking for an important photorefractive application,
several studies on electro-optic and photoconductive sol-gel responses have
been done. A very important effort has been addressed to establish the
appropriate induced-orientation procedure, in order to get the highest
electro-optic coefficient. In this way a very high coefficient of 48 pm/V at
831 nm in sol-gel has been already found. Similarly, the importance of the
non-linear chromophore concentration into the material electro-optic behavior
has been studied. However, the influence of the orientation procedure and the
chromophore concentration over the photoconductive response has not been
performed. In this work we study the vacuum-surface-charge-transport under and
without illumination after poling times of 10, 30 and 120 min on
DR1-functionalized sol-gel thin films of 1.3 um in thickness with a suitable
concentration of DR1. We include the measures before poling for other
chromophore concentrations. We found the largest density of photocurrent at 633
nm for a poling time of 30 min. We also measured the order parameter in order
to follow the Corona induced orientation evolution as function of time for each
case. The saturation found into this parameter and into the photoconduction
show the existence of an optimal poling time.
