Blind-FROG inversion of hybrid-CARS spectrograms enables spectral super-resolution without pulse shaping

Hybrid coherent anti-Stokes Raman scattering (CARS) suppresses the non-resonant background by probing vibrational coherence at finite delay, yet quantitative readout is often constrained by probe-bandwidth convolution and by reliance on additional hardware or reference measurements. Here we demonstrate a hybrid-CARS spectrogram-inversion readout enabled by blind frequency-resolved optical gating (FROG) reconstruction, which treats the measured delay-frequency spectrogram as a blind gated time-frequency trace and jointly retrieves the complex molecular excitation profile and the probe field from standard, unshaped measurements. The joint inversion removes the probe footprint from the reconstructed response, yielding quantitative, background-free Im[χ⁽³⁾] with spectral discrimination beyond conventional probe-limited readout. We experimentally recover high-fidelity Im[χ⁽³⁾] spectra of benzene and pyridine using only a femtosecond Ti:sapphire oscillator and a thick-crystal SHG probe, without pulse shaping or aggressive spectral filtering. This self-referenced approach is robust to probe dispersion and common measurement imperfections, reducing the experimental overhead for quantitative coherent Raman spectroscopy.