Generation of Paired Photons with Controllable Waveforms

We describe experiments and theory showing the generation of counterpropagating paired photons with coherence times of about 50 ns and waveforms that are controllable at a rudimentary level. Using cw lasers, electromagnetically induced transparency and cold ${}^{87}\mathrm{Rb}$ atoms we generate paired photons into opposing single-mode optical fibers at a rate of $\sim 12000$ pairs per second.

Figure 1

Intensity correlation function for a spontaneous down-converter with a relative group delay $L/V_g$ and paired emission rate $R$.

Figure 2

In the presence of strong pump and coupling lasers, phase-matched, counterpropagating Stokes and anti-Stokes photons are generated into opposing single-mode fibers and detected by single photon-counting modules (SPCM). Filters ${\mathcal{F}}_1$ and ${\mathcal{F}}_2$ are narrow-band interference filters at 780 and 795 nm, respectively.

Figure 3

Correlation function in the oscillatory regime. Coincidence rate $R_c(\tau )$ as a function of the time difference between the detection of anti-Stokes and Stokes photons is shown at $N\sigma L=11$. Data were collected over 200 sec with a duty cycle of 10% and a bin size of 1 ns. Theoretical curves (solid lines) have been scaled vertically by a common factor.

Figure 4

Correlation function in the group delay regime. Coincidence rate $R_c(\tau )$ as a function of the time difference between the detection of anti-Stokes and Stokes photons is shown at $N\sigma L=11$. Data were collected over 200 sec, and the bin size is 1 ns. Theoretical curves are vertically scaled.