We demonstrate an efficient fiber-coupled source of nondegenerate polarization-entangled photons at 795 and 1609 nm using bidirectionally pumped parametric down-conversion in bulk periodically poled lithium niobate. The single-mode source has an inferred bandwidth of 50 GHz and a spectral brightness of 300 pairs/s/GHz/mW of pump power that is suitable for narrowband applications such as entanglement transfer from photonic to atomic qubits.

We demonstrate self-phase locking in a type II phase-matched optical parametric oscillator by mutual injection locking. An intracavity quarter-wave plate provides polarization mixing between the orthogonally polarized signal and idler that induces signal-idler self-phase locking when their frequency difference is within the capture range. We observed two distinct phase states that differ in their oscillator thresholds and their signal-idler phase differences, in good agreement with theory.

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We demonstrate efficient generation of collinearly propagating, highly nondegenerate photon pairs in a periodically poled lithium niobate cw parametric downconverter with an inferred pair generation rate of 1.4x10(7)/s/mW of pump power. Detection of an 800-nm signal photon triggers a thermoelectrically cooled 20%-efficient InGaAs avalanche photodiode for the detection of the 1600-nm conjugate idler photon. Using single-mode fibers as spatial mode filters, we obtain a signal-conditioned idler-detection probability of ~3.1%.

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