Chromatic aberration compensation in multiplex coherent Raman microscopy using a Bessel beam.

Multiplex coherent anti-Stokes Raman scattering (CARS) microscopy enables label-free spectroscopic imaging over an ultra-broadband range using a supercontinuum light source. However, under high numerical aperture conditions, chromatic aberration causes axial splitting of the illumination spot, leading to missing or significantly weakened peaks. Here, we used Bessel beam illumination to compensate for chromatic aberration without modifying objective lenses. Our numerical and experimental results demonstrate that combining the nonlinear nature of the CARS process with the axial elongation of the Bessel beam spot simultaneously achieves broadband spectroscopy and high spatial resolution imaging. This approach is expected to further expand the applicability of vibrational spectroscopic imaging technique.