Pancharatnam-Berry geometric phase memory based on spontaneous parametric down-conversion

• Published in: Optics letters 2020-02, Vol.45 (3), p.682-685
• Main Authors: Qi, Wen-Rong, Liu, Rui, Kong, Ling-Jun, Wang, Zhou-Xiang, Huang, Shuang-Yin, Tu, Chenghou, Li, Yongnan, Wang, Hui-Tian
• Format: Article
• Language: English
• Subjects: Coherence; Conversion; Crystals; Photons; Signal processing
• ISSN: 0146-9592; 1539-4794
• DOI: 10.1364/OL.384363

Phase memory is an effect in which the interaction between a coherent pump beam and a nonlinear crystal generates photon pairs via the spontaneous parametric down-conversion process, then the down-converted photons (signal and idler) can carry the phase information of the pump beam. There has been much research on the memory of the dynamic phase so far; however, there is no report on the memory of non-dynamic phase, to the best of our knowledge. Here we acquire a Pancharatnam-Berry (PB) geometric phase in a physical system when light travels along a trajectory in polarization-state space. Induced coherence occurs in a cascaded scheme composed of two nonlinear crystals, when the idler photons in both crystals are aligned to be indistinguishable. A NOON ($N\; = \;{2}$N=2) state is established when blocking the two idler photons. We explore the PB geometric phase memory of the NOON state and induced coherence. We find that the first-order interference of the two-photon state or signal photons can be controlled by introducing the PB geometric phase to the pump light. This may facilitate precise control of the phase of the down-converted photons.