Superluminal evanescent modes

Signals conveyed by evanescent modes can travel faster than light. Some special features of signals are introduced and it is shown that frequency band limitation of signals is a fundamental property. Evanescent modes are characterized by extraordinary properties: Their energy is negative, they are not directly measurable, and the evanescent region is not causal since the modes traverse this region instantaneously. The study demonstrates the necessity of quantum mechanics in order to understand the superluminal signal velocity of apparently classical evanescent modes.