Stopping Narrow-Band X-Ray Pulses in Nuclear Media

A control mechanism for stopping x-ray pulses in resonant nuclear media is investigated theoretically. We show that narrow-band x-ray pulses can be mapped and stored as nuclear coherence in a thin-film planar x-ray cavity with an embedded ${}^{57}\mathrm{Fe}$ nuclear layer. The pulse is nearly resonant to the 14.4 keV Mössbauer transition in the ${}^{57}\mathrm{Fe}$ nuclei. The role of the control field is played here by a hyperfine magnetic field which induces interference effects reminiscent of electromagnetically induced transparency. We show that, by switching off the control magnetic field, a narrow-band x-ray pulse can be completely stored in the cavity for approximately 100 ns. Additional manipulation of the external magnetic field can lead to both group velocity and phase control of the pulse in the x-ray cavity sample.

Figure 1

Thin-film planar cavity setup with x-ray grazing incidence. The cavity consists of a sandwich of Pd and C layers with a 1 nm layer containing ${}^{57}\mathrm{Fe}$ placed at the antinode of the cavity. The nuclei experience a hyperfine magnetic field $\overrightarrow{B}$ (red horizontal arrow). Inset: ${}^{57}\mathrm{Fe}$ level scheme with hyperfine splitting. This is equivalent to a $V$-like three-level scheme comprising the common ground state and the two excited states (1).

Figure 2

Reflectivity spectra calculated with conuss (solid blue line) and the quantum cavity model (dashed red line) for the incident angle $\phi$. The considered cavity structure is $\mathrm{Pd}(5\mathrm{nm})/\mathrm{C}(20\mathrm{nm})/\mathrm{Fe}(1\mathrm{nm})/\mathrm{C}(20\mathrm{nm})/\mathrm{Pd}(30\mathrm{nm})$ and $B=6.4\mathrm{T}$.

Figure 3

Propagation dynamics of the polariton field $\mathrm{\Psi }$ (a) and the Rabi frequency $\mathrm{\Omega }$ of the pulse (b). The magnetic field is switched off at $t=1.3{\tau }_0$ and switched back on at $t=2.2{\tau }_0$.