The creation of monolithically integratable sources of single and entangled photons is a top research priority with formidable challenges: The production, manipulation, and measurement of the photons should all occur in the same material platform, thereby fostering stability and scalability. Here we demonstrate efficient photon pair production in a semiconductor platform, gallium arsenide. Our results show type-I spontaneous parametric down-conversion of laser light from a 2.2 mm long Bragg-reflection waveguide, and we estimate its internal pair production efficiency to be 2.0×10(-8) (pairs/pump photon). This is the first time that significant pair production has been demonstrated in a structure that can be electrically self-pumped and which can form the basis for passive optical circuitry, bringing us markedly closer to complete integration of quantum optical technologies.

Creating miniature chip scale implementations of optical quantum information protocols is a dream for many in the quantum optics community. This is largely because of the promise of stability and scalability. Here we present a monolithically integratable chip architecture upon which is built a photonic device primitive called a Bragg reflection waveguide (BRW). Implemented in gallium arsenide, we show that, via the process of spontaneous parametric down conversion, the BRW is capable of directly producing polarization entangled photons without additional path difference compensation, spectral filtering or post-selection. After splitting the twin-photons immediately after they emerge from the chip, we perform a variety of correlation tests on the photon pairs and show non-classical behaviour in their polarization. Combined with the BRW's versatile architecture our results signify the BRW design as a serious contender on which to build large scale implementations of optical quantum processing devices.

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Techniques used to assist phase matching of second-order nonlinearities in semiconductor waveguides are reviewed. The salient points of each method are highlighted, with their strengths and weaknesses with regard to various key applications discussed. Recent progress in these techniques is also reviewed. Emphasis is placed on two techniques, namely quasi-phase matching via domain disordering utilizing quantum well intermixing, and exact phase matching using Bragg reflection waveguides.The figure shows (a) An optical microscope image of an ion implantation mask used to fabricate gratings used for quasiphase matching, (b) a scanning electron micrograph of an ion implantation mask, (c) a scanning electron micrograph of a semiconductor ridge waveguide structure, and (d) an optical microscope image of group monolithic ring lasers designed for integration with quasiphase matched structures.

We propose a method of generating maximally-polarization-entangled states by type-II spontaneous parametric down-conversion in Bragg reflection waveguides. Analytic expressions for the group velocities of down-converted modes are used to engineer zero group-velocity mismatch at the operating point, making the spectra of photons within a down-converted pair indistinguishable and thus leading to a maximally-polarization-entangled state. The results can be used for the creation and manipulation of polarization-entangled qubits entirely on a chip.