AMPLIFICATION OF HIGH-ORDER RAINBOWS OF A CYLINDER WITH AN ELLIPTIC CROSS-SECTION

The intensity of high-order rainbows for normally incident light and c ertain rotation angles of a cylinder with an elliptical cross section is greatly amplified with respect to the intensity for a circular cros s-sectional cylinder. The amplification is due to a number of the inte rnal reflections occurring past the critical angle for total internal reflection, and the effect is especially strong for odd-order rainbows , beginning with the third order. Experimentally, the fourth-and the f ifth-order rainbows of a nearly elliptical cross-sectional glass rod w ere observed and analyzed. (C) 1998 Optical Society of America.