Figure 1

(Color online) (a) The BEC was end-pumped by a focused, circularly polarized laser beam, and the backscattered light was directed through a quarter wave plate $(\mathrm{L}∕4)$ and polarizing beam splitter (PBS) onto a sensitive photodetector (PD). (b) Traces from PD are shown for low and high pump powers at a detuning of $\delta =-2\pi \times 2.6\mathrm{GHz}$. Simulations for the same parameters are presented as red dash-dotted lines. Absorption images after $45\mathrm{ms}$ time of flight (TOF) of the corresponding atomic distributions are shown in (c) (low power, pump pulse duration $200\mu \mathrm{s}$) and (d) (high power, pump pulse duration $50\mu \mathrm{s}$). Circles indicating the separation of adjacent momentum orders after $45\mathrm{ms}$ TOF are shown in (d); note that they originate from the input light end $(x=0)$ of the BEC.Reuse & Permissions

Figure 2

(Color online) (a) Experimental (symbols) and simulated (lines) peak photon flux of the first superradiant pulse as a function of detuning for $R=2.2$ (circles, solid line), 6.4 (right triangles, dashed line), 10.7 (upward triangles, dotted line), and 15.9 (squares, dash-dotted line) $\times {10}^3{\mathrm{s}}^{-1}$. Error-bar limits are the standard error of the mean of five realizations and for clarity are omitted in the low-detuning portion of the graph. (b) Traces corresponding to the flat portion of (a). The detuning was $\delta =-2\pi \times 2.6\mathrm{GHz}$, for $R=2.2,4.3,6.4,8.6,10.7,15.9\times {10}^3{\mathrm{s}}^{-1}$. For clarity, the traces are edited to show only the first pulse. (c) Traces corresponding to the decaying portion in Fig. 2a. For $R=2.2\times {10}^3{\mathrm{s}}^{-1}$ and detunings $\delta =-2\pi \times 2.0$ (black), 1.0 (red), 0.7 (blue), 0.5 (green) GHz.Reuse & Permissions

Figure 3

(Color online) Snapshots of system dynamics inside the sample for high detuning $\delta =-2\pi \times 2\mathrm{GHz}$ [(a) and (c)] and low detuning $\delta =-2\pi \times 294\mathrm{MHz}$ [(b) and (d)] at the same rate $R=2.2\times {10}^3{\mathrm{s}}^{-1}$ after an interaction time $t=87\mu \mathrm{s}$. (a) and (b) show atomic densities in the momentum modes: ${\mid {\psi }_{-2}\mid }^2$ (dash-dotted line), and ${\mid {\psi }_0\mid }^2$ (solid line), ${\mid {\psi }_2\mid }^2$ (dashed line), and ${\mid {\psi }_4\mid }^2$ (dotted line). (c) and (d) display the light flux $(\propto {\mid e_{\pm }\mid }^2)$ within the sample for pump light $e_{+}$ [solid lines; in (c), red line and left axis] and reflected light $e_{-}$ [dashed lines; right scale in (c)]. Note the shared scale of $e_{-}$ in (c) and both $e_{+}$ and $e_{-}$ in (d).Reuse & Permissions