The sensitivity of classical Raman spectroscopy methods, such as coherent anti-stokes Raman spectroscopy (CARS) or stimulated Raman spectroscopy (SRS), is ultimately limited by shot-noise from the stimulating fields. We present the complete theoretical analysis of a squeezing-enhanced version of Raman spectroscopy that overcomes the shot-noise limit of sensitivity with enhancement of the Raman signal and inherent background suppression, while remaining fully compatible with standard Raman spectroscopy methods. By incorporating the Raman sample between two phase-sensitive parametric amplifiers that squeeze the light along orthogonal quadrature axes, the typical intensity measurement of the Raman response is converted into a quantum-limited, super-sensitive estimation of phase. The resonant Raman response in the sample induces a phase shift to signal-idler frequency-pairs within the fingerprint spectrum of the molecule, resulting in amplification of the resonant Raman signal by the squeezing factor of the parametric amplifiers, whereas the non-resonant background is annihilated by destructive interference. Seeding the interferometer with classical coherent light stimulates the Raman signal further without increasing the background, effectively forming squeezing-enhanced versions of CARS and SRS, where the quantum enhancement is achieved on top of the classical stimulation.

诸如相干抗焦炭拉曼光谱（CARS）或受激拉曼光谱（SRS）等经典拉曼光谱方法的灵敏度最终受到来自刺激场的散粒噪声的限制。我们介绍了拉曼光谱的挤压增强版的完整理论分析，该理论通过增强拉曼信号和固有背景抑制力克服了灵敏度的散粒噪声限制，同时仍与标准拉曼光谱方法完全兼容。通过在两个沿正交正交轴挤压光的相敏参量放大器之间合并拉曼采样，典型的拉曼响应强度测量将转换为量子受限的超灵敏相位估计。样品中的共振拉曼响应引起分子指纹谱内信号空转频率对的相移，从而导致共振拉曼信号被参量放大器的压缩因子放大，而非共振背景是被破坏性干扰歼灭。用经典相干光播种干涉仪可以进一步刺激拉曼信号，而不会增加背景，有效地形成了压缩增强型的CARS和SRS，在经典刺激的基础上实现了量子增强。而非共振背景则被破坏性干扰所消灭。用经典相干光播种干涉仪可以进一步刺激拉曼信号，而不会增加背景，有效地形成了压缩增强型的CARS和SRS，在经典刺激的基础上实现了量子增强。而非共振背景则被破坏性干扰所消灭。用经典相干光播种干涉仪可以进一步刺激拉曼信号，而不会增加背景，有效地形成了压缩增强型的CARS和SRS，在经典刺激的基础上实现了量子增强。