Repository logo

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

Published version

Repository DOI

Change log


Vasil'ev, Peter P 
Penty, Richard V 
White, Ian H 


This paper reports the observation of ultra-superluminal pulse propagation in multiple-contact semiconductor heterostructures in a superradiant emission regime, and shows definitively that it is a different class of emission from conventional spontaneous or stimulated emission. Coherent population gratings induced in the semiconductor medium under strong electrical pumping have been shown to cause a major decrease of the group refractive index, in the range of 5-40%. This decrease is much greater than that caused by conventional carrier depletion or chirp mechanisms. The decrease in refractive index in turn causes faster-than-c propagation of femtosecond pulses. The measurement also proves the existence of coherent amplification of electromagnetic pulses in semiconductors at room temperature, the coherence being strongly enhanced by interactions of the light with coherent transient gratings locked to carrier gratings. This pulse-generation technique is anticipated to have great potential in applications where highly coherent femtosecond optical pulses must be generated on demand.



phase transition, population grating, superluminal propagation, superradiance

Journal Title

Light Sci Appl

Conference Name

Journal ISSN


Volume Title



Springer Science and Business Media LLC
Engineering and Physical Sciences Research Council (EP/E064361/1)
We acknowledge support of the UK Engineering and Physical Sciences Research Council