Breaking the delay-bandwidth limit in a photonic structure

Storing light on-chip, which requires that the speed of light be significantly slowed down, is crucial for enabling photonic circuits on-chip. Ultraslow propagation(1-3) and even stopping(4,5) of light have been demonstrated using the electromagnetically induced transparency effect in atomic systems(1,3-5) and the coherent population oscillation effect in solid-state systems(2). The wavelengths and bandwidths of light in such devices are tightly constrained by the property of the material absorption lines, which limits their application in information technologies. Various slow-light devices based on photonic structures have also been demonstrated(6-10); however, these devices suffer a fundamental trade-off between the transmission bandwidth and the optical delay. It has been shown theoretically(11-13) that stopping light on-chip and thereby breaking the fundamental link between the delay and the bandwidth can be achieved by ultrafast tuning of photonic structures. Using this mechanism, here we report the first demonstration of storing light using photonic structures on-chip, with storage times longer than the bandwidth-determined photon lifetime of the static device. The release time of the pulse is externally controlled.