  Raman spectroscopy is one of the key techniques in the study of vibrational
modes and molecular structures. In Coherent Anti-Stokes Raman Scattering (CARS)
spectroscopy, a molecular vibrational spectrum is resolved via the third-order
nonlinear interaction of pump, Stokes and probe photons, typically using a
complex experimental setup with multiple beams and laser sources. Although CARS
has become a widespread technique for label-free chemical imaging and detection
of contaminants, its multi-source, multi-beam experimental implementation is
challenging. In this work we present a simple and easily implementable scheme
for performing single-beam CARS spectroscopy and microscopy using a single
femtosecond pulse, shaped by a tunable narrowband notch filter. As a substitute
for multiple sources, the single broadband pulse simultaneously provides the
pump, Stokes and probe photons, exciting a broad band of vibrational levels.
High spectroscopic resolution is obtained by utilizing a tunable spectral
notch, shaped with a resonant photonic crystal slab filter, as a narrowband,
time-delayed probe. Using this scheme the entire vibrational spectrum can be
resolved in a single-shot multiplexed measurement, circumventing the need for a
multi-source configuration or a complex pulse-shaping apparatus. We demonstrate
high-resolution single-beam micro-spectroscopy and vibrational imaging of
various samples in the 300cm^{-1}-1000cm^{-1} spectral range.
