This work will describe methodologies founded on time-frequency correlation also offer inspiration for classical target detection protocols with significantly higher source power, thereby extending the detection range. Remarkably, classical correlated probe-reference light, despite appearing random and chaotic, can reconstruct sub-Hz level single-frequency SFG output. In contrast, uncorrelated noise light doesn't undergo SFG and is entirely rejected. Consequently, background noise can be effectively distinguished, leading to a rejection capability exceeding 100dB, while the SFG process achieves nearly 100% efficiency in converting true probe photons.
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