Effect of coherence on the superluminal propagation of light pulses through anomalously dispersive media with gain

¹ Department of Physics, Hong Kong Baptist University Kowloon Tong, Hong Kong, PRC
² Department of Physics, Nanchang University - Nanchang 330047, PRC
³ Institute of Optics, Department of Physics, Zhejiang University Hangzhou 310028, PRC

Received: 24 July 2002
Accepted: 1 October 2002

Abstract

The propagation of pulses through dispersive media was investigated by solving Maxwell's equations without any approximation. It was demonstrated that the superluminal or subluminal pulse propagation originates essentially from the interference of the different frequency components of the pulse. The coherence of the different frequency components plays an important role in superluminal propagation. When the pulse becomes partially coherent, the propagation changes from superluminal to subluminal. Since superluminality always exists as long as the spectrum of the coherent pulse is within the anomalously dispersive region whatever the shape of the pulse is, such a coherent pulse must be transmitted superluminally.