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

TL;DR

This paper provides a theoretical analysis of generating mid-infrared spectrally-uncorrelated biphotons using doped lithium niobate crystals, highlighting how doping ratios influence phase-matching and group-velocity matching for quantum photonics applications.

Contribution

It introduces the use of doping ratios as a new degree of freedom to manipulate biphoton spectral properties in MIR quantum light sources.

Findings

Doping ratio significantly affects group-velocity-matching wavelengths.

InZnLN crystal's GVM2 wavelength tunable over 678.7 nm, surpassing temperature-based methods.

Doped LN crystals can produce pure single-photon and entangled photon sources for MIR quantum technologies.

Abstract

We theoretically investigate the preparation of mid-infrared (MIR) spectrally-uncorrelated 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 GVM2 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.