Optically controlled delays for broadband pulses

We propose a scheme that provides large controllable delays for broadband optical pulses. The system is based on the steep dispersion of a coherently driven medium, in which the narrow electromagnetically induced transparency (EIT) band is overcome by using spatial and temporal processing.

Figure 1

(Color online) Schemes providing a continuous controllable delay to a broadband optical pulse.

Figure 2

(Color online) (A) The beam of light has a Gaussian profile along $x$ axis. Each ray in the dispersion region consists of all frequencies ${\omega }_x$ that come from the transverse rays dispersed by the prisms. The solid line corresponds to the center of the probe beam, the dashed line is shifted at the distance $x$ from the center of the beam. The D-region is the dispersive region where different frequencies of the probe pulse are separated. (B) The spectra of the probe pulse are shown in different locations of the D-region (1-5). The dashed lines show the positions of the maximum and the maximum amplitudes of the probe pulses correspondingly, visualizing the spectral distribution of the probe pulse along the $x$-axis. The total width of the spectra is determined by the duration of the probe pulse. The spectral width of the probe pulse at a particular location is determined by the frequency dispersion of the system of prisms. (C) A three-level atomic medium with inhomogeneous magnetic field. It is shown that at different locations inside medium (1-5) the probe transition has different frequency, ${\omega }_{ab}={\omega }_{ab0}+\alpha x$, that are in resonance with the corresponding frequency component of the probe field, ${\omega }_L={\omega }_0+\beta x$, via the system of prisms shown in Fig. 1.

Figure 3

(Color online) (A) Input pulse $(T=5\mathrm{ns})$ is shown. (B) Delay time ${\tau }_{\text{delay}}=k\eta \gamma L∕2{\Omega }^2=0.65\mu \mathrm{s}$. The output pulses corresponding to different driving power are shown: (a) $\Omega T=5$, (b) $\Omega T=25$, (c) $\Omega T=100$.