Article

Non-collinear and non-degenerate polarization-entangled photon generation via concurrent type-I parametric downconversion in PPLN

Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts, United States
Optics Express (Impact Factor: 3.49). 11/2006; 14(21):10060-72. DOI: 10.1364/OE.14.010060
Source: PubMed

ABSTRACT A periodically poled lithium niobate (PPLN) crystal has been used as an efficient source of non-collinearly generated polarization-entangled photon pairs at 810 and 1550 nm. The PPLN crystal was endowed with a specially designed poling pattern and the entangled photons were generated via the nonlinear optical process of spontaneous parametric down conversion (SPDC). A novel design based on overlapping two concurrent type-I quasi-phase-matching structures in a single PPLN crystals produced correlated pairs of alternatively polarized photons in largely separated spectral regions. The phase of the resulting two-photon state is directly linked to parameters of the nonlinear grating. Continuous tunability of the generated Bell state, from Phi(+) to Phi(-), has been demonstrated by translating a slightly wedged crystal perpendicular to the pump beam.

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    • "Earlier, periodically poled lithium niobate (PPLN) waveguide structures were suggested for producing spontaneous parametric down-conversion [30] and the conditions required for generating counterpropagating entangled photons from an unguided pump field were established [31]. Furthermore, the generation of non-collinear and non-degenerate polarization-entangled photons via concurrent Type-I parametric down-conversion was demonstrated in a PPLN crystal [32]. The use of lithium niobate photonic circuits has a number of merits: 1) the properties of the material are well-understood since it has low loss and has long been the basis of integratedoptics technology [33], [34, Chap. "
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    • "Moreover, lithium niobate offers a number of ancillary advantages: 1) its properties are well-understood since it is the basis of integrated-optics technology [16]; 2) circuit elements, such as two-mode waveguides and polarization-sensitive mode-separation structures, have low loss [2]; 3) it exhibits an electro-optic effect that can modify the refractive index at rates up to tens of GHz and is polarization-sensitive [17, Sec. 20.1D]; and 4) periodic poling of the secondorder nonlinear optical coefficient is straightforward so that phase-matched parametric interactions [18] [19], such as SPDC and the generation of entangled-photon pairs [20] [21], can be readily achieved. Moreover, consistency between simulation and experimental measurement has been demonstrated in a whole host of configurations [22] [23] [24] [25] [26]. "
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