negative crystal
3.Optical measurements indi- cate that the optical features of each organic material is similar to those of the monoaxial optical-negative-crystal usually,and approach to those of the materials with twin axes during the anthrazite period.
4.1. The dissertation discussed the theories of second-harmonic generation for negative uniaxial optical crystal and summarized properties of nonlinear optical crystals, which are subjected to ultraviolet second-harmonic generation, and represented the Theorizational Law of Double Frequency Crystal Select (TLDFCS). At present, BBO crystal is the most subjected to commercial crystal of ultraviolet second-harmonic generation according to compared KDP, BBO, CLBO, KABO and KBBF crystals based on TLDFCS.
5.By controlling the length-width ratio of grating electrode and the parameters of potential pulse,the alternated structure of the positive and negative ferroelectric domains,with the duty ratio of 1∶1,can be obtained on the crystal plate surface or in certain depth of the crystal,therefore the qusai-phase matching can be achieved.
