GPU加速截断维格纳动力学下关联泵浦作用的激光相图
Phase diagram of lasing under correlated pump from GPU-accelerated Truncated Wigner dynamics
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中文总结 AI 辅助
该研究利用GPU加速截断维格纳近似，对N个两能级原子链的空间关联泵浦激光系统进行全扫描，发现泵浦关联范围可调节驱动强度、加热与光学相干性的权衡，α≈1时仍可实现完全相干光。
中文摘要 AI 辅助
超辐射（SR）激光器将光学相干性存储在原子介质而非腔场中，但维持粒子数反转的非相干泵浦存在权衡：局域泵浦产生的相干光速率随原子数N线性增长，同时通过光子反冲加热介质；而完全集体泵浦消除了该标度关系，但将发射限制为部分相干。我们对由N个两能级原子组成的链采用空间关联泵浦在上述两种极限间插值，泵浦速率随原子间距离以幂律指数α衰减。为研究超出精确解适用范围的系统，我们采用截断维格纳近似（TWA），其独立轨迹非常适合GPU并行计算。利用这一特性，我们以可承受的计算成本对多达10^4个原子的稳态可观测量进行了全扫描。我们的发现表明，所有α值下均存在超窄发射，且随着泵浦范围缩短，相干性提升，g⁽²⁾→1至少持续到α≈1，表明完全相干光无需局域泵浦。α<1时，激光所需的驱动强度降低N^(1-α)倍，当α→1时降低log N倍，从而参数化抑制反冲加热；值得注意的是，α=1对应自由空间中耗散耦合的远场包络。因此，泵浦的关联范围可作为调节驱动强度及其引发的加热与光学相干性之间权衡的旋钮。
英文摘要
Superradiant (SR) lasers store optical coherence in the atomic medium rather than the cavity field, but the incoherent drive that sustains inversion imposes a trade-off: local pumping yields coherent light at a rate that grows linearly with the atom number $N$, heating the medium through photon recoil, whereas fully collective pumping removes this scaling but limits the emission to partial coherence. We interpolate between these limits employing a spatially correlated pump on a chain of $N$ two-level atoms, with rates decaying with distance between atoms as a power law of exponent $α$. To study systems beyond the reach of exact solutions, we employ the Truncated Wigner Approximation (TWA), whose independent trajectories are ideally suited to GPU parallelism. Harnessing this, we perform a full scan of the steady-state observables for up to $10^4$ atoms at a computational cost that is practical. Our findings indicate that ultra-narrow emission persists for all $α$, while the coherence improves as the pump becomes shorter ranged, with $g^{(2)} \to 1$ surviving at least down to $α\approx 1$, indicating that fully coherent light thus does not require local pumping. The drive strength needed for lasing is reduced by a factor $N^{1-α}$ for $α< 1$, and by $\log N$ as $α\to 1$, parametrically suppressing recoil heating; notably, $α= 1$ matches the far-field envelope of dissipative couplings in free space. The correlation range of the pump thus acts as a knob trading drive intensity, and the heating it causes, against optical coherence.
