Field-Resolved Hybrid Coherent Anti-Stokes Raman Scattering for Background-Free Retrieval of Intrinsic Raman Features and Ultrafast Molecular Dynamics

Coherent anti-Stokes Raman scattering (CARS) is a powerful tool for label-free vibrational imaging, but its spectroscopic capabilities are fundamentally limited by a trade-off between spectral resolution and temporal precision. Here, we present a field-resolved framework for hybrid CARS that overcomes this constraint by treating the delay-scanned spectrogram as a holographic record of the third-order molecular response. By retrieving both the complex probe field and the excitation profile EP(Ω), we decouple light from matter at the field level, enabling background-free recovery of intrinsic Raman line shapes. Applied to benzene and acetone, our method yields line widths of 3 cm–1 and 8 cm–1, respectively, from raw spectra broadened to ∼70 cm–1 by the broadband probe, enabling recovery of intrinsic Raman features without pulse shaping or filtering. Beyond spectral sharpening, the retrieved phase reveals frequency-dependent time shifts governed by T(Ω) = ∂ΦEP/∂Ω, reflecting the causal interference between instantaneous electronic and delayed nuclear responses. Fully self-referenced and compatible with standard hybrid-CARS setups, our approach establishes a new regime of high-resolution, phase-resolved vibrational spectroscopy with direct access to femtosecond molecular dynamics.