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Physical Review A

Design of an integrated optical source of twin photons

Ivan A. Avrutsky, Alexander V. Sergienko

Published Mar 22, 2005• 4 citations
Publisher

Abstract

The phase matching for the nonlinear process of frequency-degenerated spontaneous parametric downconversion in tunneling-coupled channel waveguides is analyzed. The use of type II nonlinear interaction with individual photons in each pair appearing in different output channels allows for constructing polarization entangled states for quantum information processing applications.

DOI
10.1103/physreva.71.033812

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The phase matching for the nonlinear process of frequency-degenerated spontaneous parametric downconversion in tunneling-coupled channel waveguides is analyzed. The use of type II nonlinear interaction with individual photons in each pair appearing in different output channels allows for constructing polarization entangled states for quantum information processing applications.
We propose a scheme for generating polarization-entangled photon pairs using a χ((2)) nonlinear photonic crystal, which is designed for enabling two concurrent quasi-phase-matched spontaneous parametric downconversion processes. Beamlike photon pairs produced from each process are collinear but noncollinear with the pump. Moreover, the source we design works in a postselection-free way and applies to both degenerate and nondegenerate cases. Combining possible waveguide technologies, our scheme may provide an integrated polarization entanglement source.
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We explore the potential of versatile and efficient entangled photon pair generation by spontaneous parametric downconversion in Bragg reflection waveguides. By employing a quantum treatment of modes in channel waveguides, and by accounting for group velocity dispersion in the modes, the quantum state of the generated biphotons is realistically calculated. The pair production rate is predicted to reach 4×108 pairs/s/nm/mW of pump light in a 2 mm-long structure, on par with or exceeding the performance of previously reported designs. This is attributable to an enhanced nonlinear interaction through tight mode confinement in the waveguide. Strategies for device performance optimization and phase matching wavelength tunability are outlined and numerically demonstrated. The proposed design platform is versatile and allows photon pair generation with controllable flux, bandwidth, Schmidt number, and degree of polarization entanglement. The possibility of monolithic integration with a diode laser pump offers a way to design an electrically pumped entangled photon source.
We report a simple scheme for direct generation of frequency-bin entangled photon pairs via spontaneous parametric downconversion. Our fabricated nonlinear optical crystal with two different poling periods can simultaneously satisfy two different, spectrally symmetric nondegenerate quasi-phase-matching conditions, enabling the direct generation of entanglement in two discrete frequency-bin modes. Our produced photon pairs exhibited Hong-Ou-Mandel interference with high-visibility beating oscillations- a signature of two-mode frequency-bin entanglement. Moreover, we demonstrate deterministic entanglement-mode conversion from frequency-bin to polarization modes, with which our source can be more versatile for various quantum applications. Our scheme can be extended to direct generation of high-dimensional frequency-bin entanglement, and thus will be a key technology for frequency-multiplexed optical quantum information processing.