  We propose to integrate the electro-optic tuning function into
polarization-entangled photon pair generation process in a periodically poled
lithium niobate (PPLN). Due to the versatility of PPLN, both the spontaneously
parametric down conversion and electro-optic polarization rotation effects
could be realized simultaneously. Orthogonally-polarized and parallel-polarized
photon pairs thus are instantly switchable by tuning the applied field. The
characteristics of the source are investigated showing adjustable bandwidths
and high entanglement degrees. Moreover, other kinds of reconfigurable
entanglement are also achievable based on suitable domain-design. We believe
the domain engineering is a very promising solution for next generation
function-integrated quantum circuits.
