Fast light

Bin Luo, Hong Mei Guo

Dispersion properties of an optical medium can be greatly changed using electromagnetically induced transparency (EIT) and other nonlinear effects. Thus, the group velocity of light pulse can be much smaller (greater or even negative) than light speed in vacuum, which is called slow (fast) light. Slow and fast light are very useful in optical processing, such as optical buffer, switching, and storage devices. Usually, slow and fast light cannot be generated simultaneously in the same medium. In this paper, we propose applicable level structures to generate controllable slow and fast light simultaneously at two frequencies, with the same polarization.

M. Donovan

Ulf Leonhardt

Thomas Zacharias, Liran Hareli, Alon Bahabad

Abstract Slow and fast light are light pulses moving at group velocities slower or faster than the speed of light in vacuum. Current methods to achieve slow and fast light are based on strong dispersion attainable in resonant systems. By defining slow and fast light based on the arrival of the expectation value of the pulse in time, an alternative route for achieving slow and fast light is experimentally demonstrated where no dispersion engineering is needed and thus can be applicable to any medium and system where light is propagating. The method is based on the phenomenon of superoscillations and entails a weak measurement of the arrival time of a light pulse. The findings can be useful for applications in telecommunication, interferometry, and laser radars.

Datang Xu, Zhengyang Bai, Guoxiang Huang

We propose a scheme to realize the storage and retrieval of light pulses in a fast-light medium via a mechanism of active Raman gain (ARG). The system under consideration is a four-level atomic gas interacting with three (pump, signal, and control) laser fields. We show that a stable propagation of signal light pulses with superluminal velocity (i.e., fast-light pulses) is possible in such a system through the ARG contributed by the pump field and the quantum interference effect induced by the control field. We further show that a robust storage and retrieval of light pulses in such a fast-light medium can be implemented by switching on and off the pump and the control fields simultaneously. The results reported here may have potential applications for light information processing and transmission using fast-light media.