Dear Prof. Hwang, Thank you for your replies. I am having problem with some textbooks in Quantum Mechanics where they define circularly polarized state as somewhat analogous to the linealy polarized state. They have stated that a right circularly polarized light will be cut-off by a Left circular polarizer but pass through a right circular polarizer without any loss in intensity. Is their assertion correct? They have mentioned that a circular polarizer is in fact a combination of a linear polarizer and a quarter-wave plate that somehow retard the propagation of light after it has been polarized. Would you please explain what essentially constitute a right circularly polarized state from a left circularly polarized state based on how the circular polarizer are made?