CONTROL OF CRYSTAL ORIENTATION IN AN ORGANIC-CRYSTAL-CORED FIBER

We have succeeded in controlling organic-crystal orientation in glass capillaries using the modified Bridgman-Stockbarger method, in which t he pulling direction of the capillary is at an angle theta to the temp erature gradient. The controllability of the crystal orientation in th e organic-crystal-cored fibre (OCCF) of 2-methyl-4-nitroaniline (MNA) was examined by the measurement of the second-harmonic generation powe r. It was confirmed that the second-harmonic power of the controlled O CCF is three times higher than that of the uncontrolled OCCF, since th e axis with the largest second-order nonlinear optical susceptibility coefficient is tilted from the fibre axis in the controlled OCCF. The control mechanism for the crystal orientation is also discussed.