Patent ID: 8786949

Claim:
A method for polarizing an electromagnetic wave having a frequency of not less than 0.1 THz and not more than 0.8 THz using a polarizer, the method comprising: a step (a) of preparing the polarizer, wherein the polarizer comprises: a sapphire single crystalline layer; and a Ca x CoO 2 crystalline layer, where x is not less than 0.15 and not more than 0.55, the Ca x CoO 2 crystalline layer is stacked on the sapphire single crystalline layer, a surface of the Ca x CoO 2 crystalline layer has a (100) plane orientation, and the Ca x CoO 2 crystalline layer has a thickness of not less than 2 micrometers and not more than 20 micrometers; and a step (b) of irradiating the polarizer with the electromagnetic wave having a frequency of not less than 0.1 THz and not more than 0.8 THz to output an output wave having only a component parallel to a c-axis direction of the sapphire single crystalline layer.