Manipulation Of Second Harmonic Waves And Entangled Photons Using Two- And Three-Dimensional Nonlinear Photonic Crystals

The nonlinear photonic crystal, also known as the optical superlattice, commonly used for optical frequency conversion, is the kind of nonlinear optical material which has a position dependent nonlinear susceptibility and position independent refractive index. The reciprocal vectors provided by the modulated structure of the nonlinear photonic crystal compensate the phase mismatch in nonlinear optical processes so that efficient frequency conversion is achieved. In recent years, as research goes on, people realize that with specifically designed structures, nonlinear photonic crystals are also capable of manipulating the spatial and temporal properties of the interacting lights during frequency conversion, especially when one dimensional modulated structures are generalized to two dimensional ones, multiple operations of the interacting lights are allowed. Based on such a research background, the thesis further develops a new method for fabricating three dimensional nonlinear photonic crystals and investigates various kinds of manipulations of both classical and quantum optical fields with two-and three-dimensional nonlinear photonic crystals. The main content of this thesis includes the followings:1) Multifunctional spatial control of entangled photons with a two dimensional nonlinear photonic crystal are studied. The structure of the multi-strip periodic poled lithium tantalate with a parabolic transverse phase profile is analyzed and the entan-gled two-photon state generated within such an structure during spontaneous paramet-ric down conversion is theoretically investigated. Experimentally, the focusing and splitting of the two-photon are demonstrated, which shows that versatile control of the entangled photons can be achieved using nonlinear photonic crystals. Meanwhile two photon NOON state is also realized. In principle, it is also possible to create many other kinds of entangled photon states through engineering the structure of nonlinear photonic crystals. Such an integration of preparation and manipulation of the entan-gled photons fits the needs of various practical applications in quantum information technology.2) New method of fabricating nonlinear photonic crystal by laser direct writing is developed. A set of technical parameters including pulse energy, repetition rate and writing speed for fabrication of nonlinear photonic crystals through laser writing are summed up. One dimensional periodic structures are fabricated in lithium niobate sam-ples and second harmonic generation experiments are carried out to characterize these structures. The result shows that laser writing successfully modulates the nonlinear coefficient of the crystal in a large volume of the sample, which indicates that it is en-tirely possible to fabricate three dimensional nonlinear photonic crystal with this laser writing method.3) Three dimensional nonlinear photonic crystal is demonstrated for the first time using laser direct writing technique. A three dimensional orthorhombic structured non-linear photonic crystal is fabricated and second harmonic generation process within this structure is investigated. Quasi phase matched nonlinear processes in three dimensional nonlinear photonic crystals are theoretically analyzed. Under several approximations, it is found out that the interacting waves follow similar behaviors as in the one-and two-dimensional case. The second harmonic experiment reveals multiple reciprocal lattice vectors of the three dimensional orthorhombic structure, especially the reciprocal lat-tice vectors along the z axis of the lithium niobate crystal, which are hardly possible to realize with conventional electric poling technique. The development of three dimen-sional quasi phase matching offers new degree of freedom and functional expansions for nonlinear photonic crystal applications in research fields such as nonlinear optics and quantum optics.