Total internal reflection enabled wide-field Coherent anti-Stokes Raman scattering microscopy

A system comprising:

• an oscillator configured to emit femtosecond (fs) pulses of light centered at a preset wavelength;
• a beam splitter disposed in a path of the emitted pulses of light and configured to split the emitted light into pulses for a pump beam and a probe beam;
• a photonic crystal fiber disposed in a path of the probe beam and configured to produce pulses for a Stokes beam, which is chirped;
• objective optics configured to:
• receive the pump beam and the Stokes beam, where the received pump beam and Stokes beam are spatially and temporally aligned,
• redirect the received pump beam and Stokes beam through a dielectric substrate towards an interface between a sample and the dielectric substrate to illuminate an area of about 20 μm×20 μm to about 100 μm×100 μm of the sample-substrate interface;
• cause total internal reflection (TIR) of the pump beam and the Stokes beam at the illuminated portion of the sample-substrate interface, wherein the sample is disposed on the dielectric substrate, where the dielectric substrate is transparent to both the pump beam and the chirped probe beam;
• and
• produce corresponding evanescent waves in a portion of the sample within 200 nm of the sample-substrate interface, wherein the portion of the sample illuminated by the evanescent waves emits coherent anti-Stokes Raman scattering (CARS) light, wherein the dielectric substrate is transparent to the CARS light emitted by the portion of the sample, and
• collect a backward-propagating beam of pulses of CARS light that propagates from the portion of the sample through the dielectric substrate towards the objective optics;
• and
• a camera configured to
• receive, from the objective optics, the backward-propagating beam, and
• produce an image of the sample having a specific image size using the received backward-propagating beam.