Investigation of 1064-nm Pumped Type II SPDC in Potassium Niobate for Generation of High Spectral Purity Photon Pairs

The generation and detection of nonclassical light of about 2 μm has good potential in an emerging field of high-sensitivity metrology, especially gravitational wave detection, as well as free-space quantum communication. A pair of photons is generated through a spontaneous parametric down-conversion (SPDC) process in a nonlinear optic crystal, which can be properly entangled in a spatial region where two beams with each polarization overlap or in a Sagnac-loop interferometer configuration. We investigated theoretically and numerically Type II SPDC in a potassium niobate (KNbO3, KN) crystal, which is useful as a material platform for generating photon pairs of high spectral purity in the 2-μm range. The technique is based on the frequency degenerate SPDC under Type II extended phase matching (EPM). We described the EPM characteristics of KN and showed that it is practically feasible for a 1064-nm pumped SPDC under moderate temperature conditions. The effective nonlinear optic coefficient of KN is at least four-times larger than those of other crystals using the Type II EPM approach, which implies a significant improvement in SPDC efficiency. The joint spectral analysis showed that a pair of photons can be generated with a high purity of 0.995 through proper pump filtering.

Особенности поляризации пьезоэлектрической керамики на основе ниобата натрия

Comparative studies of the pyroelectric properties and structural features of sodium niobate and sodium-potassium niobate ceramics obtained under different technological conditions for the synthesis of sodium niobate have been carried out. X-ray phase analysis revealed the existence of an additional phase with the chemical formula NaNb10O18 in sodium niobate ceramic samples that do not exhibit ferroelectric properties. It is shown that the temperature conditions for the synthesis of the sodium niobate material determine the nature of the macroscopic polarization of the samples of both pure sodium niobate and sodium-potassium niobate.

Enhanced polarization in epitaxially strained monoclinic potassium niobate for lead-free electromechanical applications

To further our understanding of how complex anisotropic structure-property relationships may be rationalized by their local atomic arrangements in ferroelectric materials, using the newly-found metastable monoclinic P m phase of...