Slowing down the speed of light using an electromagnetically-induced-transparency mechanism in a modified reservoir

We propose an effective method to achieve extremely slow light by using both the mechanism of electromagnetically induced transparency (EIT) and the localization of a coupled cavity waveguide (CCW). Based on quantum mechanics theory and the dispersion relation of a CCW, we derive a group-velocity formula that reveals both the effects of the EIT and CCW. Results show that ultralow light velocity at the order of several meters per second or even static light, could be obtained feasibly. In comparison with the EIT mechanism in a background of vacuum, this proposed method is more effective and realistic to achieve extremely slow light. And it exhibits potential values in the field of light storage.

Figure 1

Schematic sketch of the extremely-slow-light system. (a) The coupled cavity waveguide along the horizontal direction. (b) The irreducible Brillouin zone, and the special points $\mathrm{\Gamma }$ and $X$. (c) The three-level atomic system in the cavities. (d) A probe light of ${\omega }_p$ in the transmission mode and a localized control light of ${\omega }_c$. (e) The same as panel (d) except for the probe light is in the localized cavity mode.

Figure 2

The photonic band structure for a CCW composed of dielectric columns with the radius $r=0.2a$, the dielectric constant $\epsilon =8.9$, and the size of a unit cell is $R=5a$, as shown in Fig. 1.

Figure 3

Transmission spectrum of a three-cavity CCW.

Figure 4

Field distribution (normalized with the maximum of the electric-field density) of incident light with $\omega =0.39615(2\pi c/a)$ in a three-cavity CCW, where both $x$ and $y$ coordinates are scaled by the the lattice constant $a$.

Figure 5

$\mathrm{Im}\left(\chi \right)$ as a function of $kx$ for the parameters $\mathrm{\Delta }=2\gamma$: (a) $B=10\gamma$, (b) $B=20\gamma$, (c) $B=100\gamma$, and (d) $B=1000\gamma$.

Figure 6

(a), (b) Imaginary (red dashed line) and real (blue solid line) parts of the complex polarizability $\chi$ changing with the detuning $\mathrm{\Delta }$: (a) $B=\gamma$, (b) $B=0.2\gamma$. (c), (d) Delay time per unit length, $T_{\mathrm{del}}$, as a function of the detuning $\mathrm{\Delta }$, where $\zeta =N_a{\left|{\vec{\mu }}_{21}\right|}^2/{\epsilon }_0\hslash {\gamma }^2$. (c) $B=\gamma$. (d) $B=0.2\gamma$.

Figure 7

Changes of the group velocity $v_g^{\mathrm{cav}}$ with $\omega /{\omega }_0$, $B=20\gamma$, where the probe light is in the cavity mode as shown in Fig. 1.