Pulse generation with ultra-superluminal pulse propagation in semiconductor heterostructures by superradiant-phase transition enhanced by transient coherent population gratings

摘要

Scientists show for the first time that, despite superficial similarities, superradiance fundamentally differs from normal lasing. First proposed by Dicke in 1954, superradiance is the enhanced emission of light from an ensemble of excited atoms or ions. Recently, there has been debate concerning whether superradiance-like effects observed in semiconductors at room temperature are true superradiance phenomena or simply lasing. By performing measurements on a semiconductor device, Peter Vasil’ev, Richard Penty and Ian White at Cambridge University in the United Kingdom have definitively shown that such effects are superradiant. In particular, they observed a large reduction in the group refractive index, which gives rise to faster-than-c propagation of femtosecond light pulses. The researchers consider their pulse-generation technique to be highly promising for applications requiring on-demand generation of highly coherent femtosecond light pulses.