A method for proving crystal birefringence is presented. Thepolarization state of monochromatic plane electromagnetic wave is obtained for intermediate category.

The memory simulated annealing approach is presented for designing an optical FIR filter based on crystal birefringence, which is able to provide arbitrary spectrum output with double channels.

For the study of birefringence dispersion character of other aeolotropic crystal material, this method can also be applied.