Mid-infrared spectrally-uncorrelated biphotons generation from doped PPLN: a theoretical investigation

We theoretically investigate the preparation of mid-infrared (MIR) spectrallyuncorrelated biphotons from a spontaneous parametric down-conversion process using doped LN crystals, including MgO doped LN, ZnO doped LN, and In2O3 doped ZnLN with doping ratio from 0 to 7 mol%. The tilt angle of the phase-matching function and the corresponding poling period are calculated under type-II, type-I, and type-0 phase-matching conditions. We also calculate the thermal properties of the doped LN crystals and their performance in Hong-Ou-Mandel interference. It is found that the doping ratio has a substantial impact on the group-velocity-matching (GVM) wavelengths. Especially, the GVM(2) wavelength of co-doped InZnLN crystal has a tunable range of 678.7 nm, which is much broader than the tunable range of less than 100 nm achieved by the conventional method of adjusting the temperature. It can be concluded that the doping ratio can be utilized as a degree of freedom to manipulate the biphoton state. The spectrally uncorrelated biphotons can be used to prepare pure single-photon source and entangled photon source, which may have promising applications for quantum-enhanced sensing, imaging, and communications at the MIR range. (c) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

In this study, doped LN crystals were utilized to prepare spectrally uncorrelated biphotons in the MIR range. The doping ratio was found to significantly impact the thermal properties and GVM wavelengths, with the co-doped InZnLN crystal exhibiting a wide tunable range. These spectrally uncorrelated biphotons can be used for applications such as quantum-enhanced sensing, imaging, and communications in the MIR range.