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

Abstract

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.

Understanding the Correlation Between Structure and Entangled Photon Pair Properties with Metal–Organic Frameworks

“…The MOF observables shown in Tables and can be affected by temperature because the thermal lattice distortions are known to influence optical properties. − To understand how the MOF observables are affected by temperature, we have done MD simulations of all the crystal structures shown in Figure B–E at 300 K using LAMMPS (see the Methods section). We ran single point calculations to estimate the band gap of all the extracted frames.…”

Investigation of Mid-Infrared Broadband Second-Harmonic Generation in Non-Oxide Nonlinear Optic Crystals

“…For Type I, w is simply determined by the angle between the low-RI SH-beam and the high-RI F-beam, as can be appreciated from Table 3. However, for Type II, the low-RI F-beam is always placed between the high-RI F-beam and the low-RI SH-beam [60,61]. In this case, w is defined as the largest angle formed by the high-RI F-beam and the low-RI SH-beam:…”