interval e g 10 mm each torch can be either connected with the same high voltage source or different high voltage sources independent with each other compared with the single torch configuration shown fig3 the configuration shown in fig5 a is effective in poling rectangular shaped larger area crystal in fig5 b a number of torches e g 8 torches are arranged on a circle with certain angular interval e g 45 u00b0 the radius of the circle can be a value between 1 mm and 100 mm e g 10 mm each torch can be either connected with the same high voltage source or different high voltage sources independent with each other compared with the single torch configuration shown fig3 the configuration shown in fig5 b is effective in poling circular shaped larger area crystal since uniform charge distribution can be achieved over the entire u2212 c surface of the substrate by employing this configuration in fig5 c a number of torches e g 4 torches are arranged on a circle with certain angular interval e g 90 u00b0 while additional torch is set at the center of the circle the radius of the circle can be a value between 1 mm and 100 mm e g 10 mm each torch can be either connected with the same high voltage source or different high voltage sources independent with each other.