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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Entangled photon generation in a phase-modulated, quasi-phasematched crystal

Paulina S. Kuo, Jason S. Pelc, Oliver Slattery, Yong‐Su Kim, Xiao Hong Tang

Published Sep 26, 2013• 2 citations
Publisher

Abstract

We propose a scheme to generate polarization-entangled photon pairs by spontaneous parametric downconversion in a phase-modulated, type-II, quasi-phasematched (QPM) crystal. Instead of using two distinct crystals to generate |HV⟩and |VH⟩states, the phase-modulated QPM grating allows both states to be generated simultaneously in a distributed fashion throughout the nonlinear crystal. Temporal compensation is still needed to correct for effects of birefringence in the crystal. The distributed generation of the polarization-entangled photons is compared to generation using two sequential crystals.

DOI
10.1117/12.2024286

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We proposed and demonstrated a simple but deterministic scheme for generating polarization-entangled photon pairs at telecommunication wavelengths with type-II quasi-phase-matched spontaneous parametric down-conversion (QPM-SPDC) having two poling periods. We fabricated a LiNbO3 crystal having two poling periods so as to generate entangled photons at two wavelengths, i.e., 1506 nm and 1594 nm. We characterized the two-photon polarization state with state tomography and confirmed that the state was highly entangled.
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We develop and demonstrate a source of polarization-entangled photon pairs using spontaneous parametric down-conversion (SPDC) in domain-engineered, periodically poled lithium niobate (PPLN) at telecom wavelengths. Pumped at 775 nm, this domain-engineered type-II SPDC source produces non-degenerate signal and idler pairs at 1530 nm and 1569 nm. Because of birefringence, the photon pair with horizontally polarized signal and vertically polarized idler has a different phasematching condition than the pair with vertically polarized signal and horizontally polarized idler. Using phase-modulation of the domain structure, we produced a crystal that can simultaneously generate both states in a distributed fashion throughout a single crystal. Performing SPDC using this aperiodically poled crystal, we observed polarization entanglement visibility above 93%. We compare the phase-modulated crystal to other aperiodic structures, including dual-periodically-poled and interlaced biperiodic structures.