Quasi-phase-matched spontaneous parametric down-conversion in chiral ferroelectric nematic liquid crystalsKavčič, Aljaž (Avtor) Sebastián Ugarteche, Nerea (Avtor) Humar, Matjaž (Avtor) ferroelectric liquid crystalsoptical second-harmonic generationphoton pairsparametric down-conversionFor high-intensity photon pair generation via spontaneous parametric down-conversion, phase matching or quasi-phase-matching must be realized. The most common method is to use periodically poled crystals, where quasi-phase-matching is achieved through the periodic modulation of the nonlinear susceptibility. In contrast to solid-state materials typically employed, an alternative approach is demonstrated here by using chiral ferroelectric nematic liquid crystals (FNLCs). It involves the spontaneous formation of a twisted periodic arrangement of liquid crystal molecules that depends only on the concentration of chiral dopants. This enables the rapid and scalable fabrication of nonlinear optical media with a tunable periodicity of the structure. We show that within only 20µ⁢m, we can enhance the signal by 2 orders of magnitude compared to the maximal achievable rate for the non-phase-matched case. This process enables us to achieve a significantly enhanced photon pair generation rate of over 1200 Hz/mW in a very short interaction length while simultaneously maintaining a high degree of polarization entanglement. These results establish chiral FNLCs as a versatile, reconfigurable, and low-cost platform for nonlinear and quantum photonics.American Physical Society20262026-03-13 12:45:58Neznano28307UDK: 53ISSN pri članku: 2643-1564DOI: 10.1103/wgb3-clj5COBISS_ID: 271600643ZDAsl