We present a pulsed and integrated, highly non-degenerate parametric down-conversion (PDC) source of heralded single photons at telecom wavelengths, paired with heralding photons around 800 nm. The active PDC section is combined with a passive, integrated wavelength division demultiplexer on-chip, which allows for the spatial separation of signal and idler photons with efficiencies of more than 96.5%, as well as with multi-band reflection and antireflection coatings which facilitate low incoupling losses and a pump suppression at the output of the device of more than 99%. Our device is capable of preparing single photons with efficiencies of 60% with a coincidences-to-accidentals ratio exceeding 7400. Likewise, it shows practically no significant background noise compared to continuous wave realizations. For low pump powers, we measure a conditioned second-order correlation function of g (2) = 3.8 × 10 −3 , which proves almost pure single-photon generation. In addition, our source can feature a high brightness of n pulse = 0.24 generated photon pairs per pump pulse at pump power levels below 100 µW. The high quality of the pulsed PDC process in conjunction with the integration of highly efficient passive elements makes our device a promising candidate for future quantum networking applications, where an efficient miniaturization plays a crucial role.Recent progress in the field of quantum information processing has highlighted the prospects of using integrated optic devices for quantum applications [1][2][3][4][5]. Integrated quantum photonics offers several advantages in comparison with free-space experimental setups with bulk optic components [6]. The miniaturization of systems with increased complexity not only drastically reduces the required space and paves the way for future commercialization, but also enables the implementation of optical networks with a large number of optical modes and an extremely high stability.In 2008 Politi et al [7] demonstrated the first quantum interference and photonic gates onchip, whereas different groups developed sophisticated and integrated experiments with twophoton interference [8,9] or photon entanglement [10,11], controlled qubit operations [12] and the controlled phase shifts in linear optical circuits [5,13]. In 2012, Metcalf et al [14] realized the first three-photon experiment inside a linear optical network, and recent research on boson sampling in an integrated device demonstrates four-photon quantum interference [15].However, in all these experiments the preparation of the photon pairs has actually been performed outside the integrated devices employing traditional bulk crystal parametric downconversion (PDC) sources. The efficient coupling between these sources and the integrated circuit remains a bottleneck for designing systems with increasing complexity.On the other hand, remarkable efforts have been devoted to the development of integrated PDC sources for photon pair generation inside channel waveguides [16-23] over the last few decades. The main benefits of...