Abstract

The topic of controlling the speed of propagation of light is a burgeoning one, and there is much interest in particular is studying so-called “slow light”. The motivation lies in the fundamental (What does it mean for the refractive index of a medium to be a million?) to the applied (Can the extreme frequency dependence be exploited for technical applications?). The ability to probe quantum systems on short timescales is central to the advancement of quantum technology. Here we show that this is possible using an off-resonant dispersive probe. By applying a magnetic field to an atomic vapour the spectra of the group index for left and right circularly polarized light become displaced, leading to the Faraday effect. We have investigated the Faraday effect as an atomic probe in a slow light medium. The talk will review the physics of slow light and the Faraday effect, and show recent results where we demonstrate dynamic broadband pulse switching by rotating a linearly polarized nanosecond pulse by pi/2 radians with negligible distortion and transmission close to unity. (Siddons et al. Nature Photon 3, 225-229 (2009)).