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.
Highlights
The mid-infrared (MIR) wavelength range is of great interest to a variety of scientific and technological applications in sensing, imaging, and communications [1, 2]
We investigate the generation of spectrally uncorrelated biphotons from periodically poled lithium niobate (PPLN) crystals at MIR range
PPLN has the merits of large nonlinear coefficient and wide transparency range (0.4 μm ∼ 5 μm) [25,26,27,28]
Summary
The mid-infrared (MIR) wavelength range (approximately 2-20 μm) is of great interest to a variety of scientific and technological applications in sensing, imaging, and communications [1, 2]. With the rapid development of optical fiber communications, there is a growing demand to expand the communication wavelengths into the MIR region to increase the communication bandwidth [8] All these practical applications mentioned above are based on strong light sources in the MIR region. PPLN has the merits of large nonlinear coefficient and wide transparency range (0.4 μm ∼ 5 μm) [25,26,27,28] Another unique advantage of PPLN is that its intrinsical group-velocity-matched (GVM) wavelengths are in the MIR range, and the spectrally uncorrelated biphoton state can be engineered at the GVM wavelengths [14, 29]. We investigated the GVM wavelengths, the tilt angle, the poling period, the thermal properties and the HOM interferences of biphtons generated from three kinds of doped LN crystals, including MgLN [MgO(x mol%)LiNbO3], ZnLN [ZnO(x mol%)LiNbO3], and InZnLN [In2O3(x mol%)ZnO(5.5 mol%)LiNbO3, with x from 0 to 7]
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