论文标题
用宽带挤压真空吸收两光子的理论
Theory of Two-Photon Absorption with Broadband Squeezed Vacuum
论文作者
论文摘要
我们提出了一个分析性量子理论模型，用于宽带，频谱多模式挤压真空的非共鸣分子两光子吸收（TPA），包括低增生（孤立的纠缠光子对或EPP）和高增量（明亮的挤压真空吸尘器或BSV）方案。结果与纠缠灯TPA作为光谱和成像方法的潜在使用有关。我们将令人兴奋的光在空间上是单模式，并且在所有中间分子状态下都没有谐振。在高收益的情况下，我们发现，在这种情况下，最终分子状态的线宽要比令人兴奋的光的带宽要窄得多，因此发现明亮的挤压真空吸尘器同样有效地驾驶TPA，因为准单颜色相干态（经典）的临时形状和均值均值均值和均值均值，并且均值相同的临时脉冲和均值均值。因此，在这种情况下，在极低的光通量下观察TPA的优势不是由宽带明亮的挤压真空提供。在相反的情况下，最终状态线宽比BSV刺激光的带宽要宽得多，我们表明TPA速率与零时间延迟G^（2）（0）的二阶强度自相关函数成正比，如预期。我们得出描述这两种限制案例之间的过渡，即分子宽度和光学带宽是可以比较的，就像实验研究通常情况一样，我们得出了描述的公式。我们还表明，对于G^（2）（0），要达到理想化的形式G^（2）（0）= 3 + 1/n，n是每个时间模式的平均光子数量，需要补偿用于生成BSV的非线性光学晶体中固有的分散体。
We present an analytical quantum theoretic model for non-resonant molecular two-photon absorption (TPA) of broadband, spectrally multi-mode squeezed vacuum, including low-gain (isolated entangled photon pairs or EPP) and high-gain (bright squeezed vacuum or BSV) regimes. The results are relevant to the potential use of entangled-light TPA as a spectroscopic and imaging method. We treat the scenario that the exciting light is spatially single-mode and is non-resonant with all intermediate molecular states. In the case of high gain, we find that in the case that the linewidth of the final molecular state is much narrower than the bandwidth of the exciting light, bright squeezed vacuum is found to be equally (but no more) effective in driving TPA as is a quasi-monochromatic coherent-state (classical) pulse of the same temporal shape, duration and mean photon number. Therefore, in this case the sought-for advantage of observing TPA at extremely low optical flux is not provided by broadband bright squeezed vacuum. In the opposite case that the final-state linewidth is much broader than the bandwidth of the BSV exciting light, we show that the TPA rate is proportional to the second-order intensity autocorrelation function at zero time delay g^(2)(0), as expected. We derive and evaluate formulas describing the transition between these two limiting cases, that is, including the regime where the molecular linewidth and optical bandwidth are comparable, as is often the case in experimental studies. We also show that for g^(2)(0) to reach the idealized form g^(2)(0) = 3 + 1/n, with n being the mean number of photons per temporal mode, it is required to compensate the dispersion inherent in the nonlinear-optical crystal used to generate the BSV.
