從準晶到人工準晶——從2011年諾貝爾化學獎談起(2)

       2013海峽兩岸功能材料科技與產業峯會——The nonlinear crystals with modulated quadratic nonlinear coefficients x(2) are called quasi-phase-matching (QPM) materials, or optical superlattices. The concepts were first referred to by Armstrong et al and Ming et al several decades ago. Berger later extended the QPM from one dimension (1D) to 2D, and proposed the concept of x(2) photonic crystal in order to contrast and compare it with a regular photonic crystal having a periodic linear susceptibility. Since then, such a nonlinear photon crystal has become a very important artificial microstructure material applied to nonlinear optics and laser, in particular, recently in quantum optics. The x(2) photonic crystal is routinely fabricated by pattern-poling a ferroelectric crystal. The sign of x(2) in such a crystal is modulated by reversing the orientation of ferroelectric a significant enhancement of nonlinear frequency conversion efficiency by QPM, or a required wavefront of the harmonic generation, nonlinear light scattering, nonlinear Cherenkov radiation, nonlinear Talbot effect etc were regime, quantum optics. The generated entanglement photons could been controlled with full freedom offered by be realized usually in an uniform nonlinear crystal at all, therefore, it would bring revolutionary impacts on quantum optics and quantum information in future.