Santamaria Luigi, Pallotti Deborah, Siciliani de Cumis Mario, Dequal Daniele, Lupo Cosmo
Opt Express. 2023 Oct 9;31(21):33930-33944. doi: 10.1364/OE.486617.
Spatial-mode demultiplexing (SPADE) has recently been adopted to measure the separation in the transverse plane between two incoherent point-like sources with sub-wavelength separation. It has been argued that this approach may yield extraordinary performances in the photon-counting regime. Here, we explore SPADE as a tool for precision measurements in the regime of bright, incoherent sources. First we analyze the general problem of estimating the second moments of the source's intensity distribution, for an extended incoherent source of any shape. Our theory predicts a substantial improvement in signal-to-noise ratio (SNR) of SPADE over direct imaging in the sub-wavelength regime. Second, we present an experimental application of SPADE to the case of two point-like, bright sources. We demonstrate the use of this setup for the estimation of the transverse separation and for the estimation of the relative intensity, confirming the expected improvement in SNR.
空间模式解复用（SPADE）最近已被用于测量横向平面中两个非相干点状源之间的亚波长间隔。有人认为，这种方法在光子计数模式下可能会产生非凡的性能。在这里，我们探索将SPADE作为一种用于明亮非相干源模式下精密测量的工具。首先，我们分析了对于任意形状的扩展非相干源，估计源强度分布二阶矩的一般问题。我们的理论预测，在亚波长模式下，SPADE的信噪比（SNR）相对于直接成像有显著提高。其次，我们展示了SPADE在两个点状明亮源情况下的实验应用。我们证明了使用这种设置来估计横向间隔和相对强度，证实了预期的SNR提高。
