  Parametric downconversion (PDC) in semiconductor Bragg-reflection waveguides
(BRW) is routinely exploited for photon-pair generation in the
telecommunication range. Contrary to many conventional PDC sources, BRWs offer
possibilities to create spectrally broadband but nevertheless indistinguishable
photon pairs in orthogonal polarizations that simultaneously incorporate high
frequency entanglement. We explore the characteristics of co-propagating twin
beams created in a type-II ridge BRW. Our PDC source is bright and efficient,
which serves as a benchmark of its performance and justifies its exploitation
for further use in quantum photonics. We then examine the coalescence of the
twin beams and investigate the effect of their inevitable multi-photon
contributions on the observed photon bunching. Our results show that BRWs have
a great potential for producing broadband indistinguishable photon pairs as
well as multi-photon states.
