Frequency-filtered storage of parametric fluorescence with electromagnetically induced transparency

The broadband parametric fluorescence pulse (probe light) with center frequency resonant on the ${}^{87}\mathrm{Rb}$ $D_1$ line was injected into a cold atomic ensemble with coherent light (control light). Due to the low gain in the parametric down conversion process, the probe light was in a highly bunched photon-pair state. By switching off the control light, the probe light within the electromagnetically induced transparency window was mapped on the atoms. When the control light was switched on, the probe light was retrieved and frequency-filtered storage was confirmed from the superbunching effect and an increase of the coherence time of the retrieved light.

Figure 1

(Color online) Schematic diagram of experimental setup. AOM, acousto-optic modulator; LN, quasi-phase-matched $\mathrm{Mg}\mathrm{O}:\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_3$ wave guide; PBP, Pellin-Broca prism; DM, dichroic mirror; DP, dispersing prism; HG, holographic grating; PMF, polarization maintained single mode fiber; $\lambda ∕4$, quarter wave plate; ET, etalon; BS, beam splitter; SMF, single mode fiber; D1, D2, avalanche photodetectors.

Figure 2

Experimental results of intensity correlation with $1.6\mathrm{ns}$ resolution of the MCS: (a) broadband parametric fluorescence, (c) retrieved component of coherent light, and (d) retrieved component of parametric fluorescence. The insets of (a) and (d) show magnifications of the coincidences at 0 time delay. (b) Sharp coincidence peak in (a) measured with $0.1\mathrm{ns}$ resolution of the MCS.

Figure 3

(Color online) Measured transmission spectra of a weak coherent probe as a function of detuning with (solid line) and without (dotted line) the control light.

Figure 4

(Color online) Obtained probe pulses under reference (broken line), slow propagation (dotted line), and storage conditions (solid line). See text for details. The probe light was coherent light with frequency detuning of (a) $0\mathrm{MHz}$, (b) $10\mathrm{MHz}$, and (c) $100\mathrm{MHz}$. (d) The probe light was broadband parametric fluorescence. The inset of (d) shows magnification of the count rate from $600\mathrm{ns}\text{to}850\mathrm{ns}$.

Figure 5

(Color online) Integral intensities of retrieved coherent lights and photon count rates of retrieved parametric fluorescence as a function of storage time.