We introduce a quasi-phase-matched technique in quadratic nonlinear crystals, constructing an artificial gauge field by changing the inclination angle of stripes, which is realized by the positive- and negative-polarization directions of nonlinear susceptibility along the crystal. Unlike the artificial gauge field constructed through linear coupling in other settings, the gauge field in this system is realized by nonlinear coupling. We demonstrate that this gauge field can generate stable chiral solitons with chiral energy flow rotating around the solitons. In contrast to conventional chiral currents generated with the same species or frequency, the chiral currents in the present system are formed by mutual coupling between fundamental-frequency and second-harmonic components. We derive the semianalytical solution for the chiral energy flow in this system. It is found that an optimal inclination angle that can maximize the chiral energy flow under different parameters exists, and this optimal inclination shows a positive correlation with the power and detuning. The mobility and collisions of the chiral solitons are also discussed. The results show that chiral solitons move in response to kicking and undergo fully elastic collisions with each other. In addition, the possibility of experimentally generating chiral solitons and chiral currents is outlined.

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• Nonlinear optics
• Optical solitons
• Photonics