  A backward wave optical parametric oscillator (BWOPO) waveguide in
periodically poled Rb-doped KTP is presented. The waveguide exhibits low loss
(0.16 dB/cm) and has an oscillation threshold, almost 20 times lower than the
corresponding bulk device. The backward wave has a narrow linewidth of 21 GHz
at 1514.6 nm while the forward wave at 1688.7 nm has a spectrum replicating the
pump. The unique spectral features of the BWOPO will unlock novel opportunities
in low-power nonlinear integrated optics. A conversion efficiency of 8.4% was
obtained limited by the emergence of backward stimulated polariton scattering.
