  We report the effect of $\delta$-doping at LaAlO$_{3}$/SrTiO$_{3}$ interface
with LaMnO$_{3}$ monolayers on the photoconducting (PC) state. The PC is
realized by exposing the samples to broad band optical radiation of a quartz
lamp and 325 and 441 nm lines of a He-Cd laser. Along with the significant
modification in electrical transport which drives the pure
LaAlO$_{3}$/SrTiO$_{3}$ interface from metal-to-insulator with increasing
LaMnO$_{3}$ sub-monolayer thickness, we also observe an enhancement in the
photo-response and relaxation time constant. Possible scenario for the PC based
on defect-clusters, random potential fluctuations and large lattice relaxation
models have been discussed. For pure LaAlO$_{3}$/SrTiO$_{3}$, the
photoconductivity appears to originate from inter-band transitions between
Ti-derived $3d$ bands which are $e_{g}$ in character and O 2p - Ti $t_{2g}$
hybridized bands. The band structure changes significantly when fractional
layers of LaMnO$_{3}$ are introduced. Here the Mn $e_{g}$ bands ($\approx1.5$
eV above the Fermi energy) within the photo-conducting gap lead to a reduction
in the photo-excitation energy and a gain in overall photoconductivity.
