  The practical prospect of quantum communication and information processing
relies on sophisticated single photon pairs which feature controllable
waveform, narrow spectrum, excellent purity, fiber compatibility and
miniaturized design. For practical realizations, stable, miniaturized, low-cost
devices are required. Sources with one or some of above performances have been
demonstrated already, but it is quite challenging to have a source with all of
the described characteristics simultaneously. Here we report on an integrated
single-longitudinal-mode non-degenerate narrowband photon pair source, which
exhibits all requirements needed for quantum applications. The device is
composed of a periodically poled Ti-indiffused lithium niobate waveguide with
high reflective dielectric mirror coatings deposited on the waveguide
end-faces. Photon pairs with wavelengths around 890 nm and 1320 nm are
generated via type II phase-matched parametric down-conversion. Clustering in
this dispersive cavity restricts the whole conversion spectrum to one
single-longitudinal-mode in a single cluster yielding a narrow bandwidth of
only 60 MHz. The high conversion efficiency in the waveguide, together with the
spectral clustering in the doubly resonant waveguide, leads to a high
brightness of $3\times10^4~$pairs/(s$\cdot$mW$\cdot$MHz). This source exhibits
prominent single-longitudinal-mode purity and remarkable temporal shaping
capability. Especially, due to temporal broadening, we can observe that the
coherence time of the two-photon component of PDC state is actually longer than
the one of the single photon states. The miniaturized monolithic design makes
this source have various fiber communication applications.
