Optimal control of coherent anti-Stokes Raman scattering image contrast

Optimal control of CARS image contrast is reported. The setup combines an evolutionary strategy and a closed-loop feedback with a liquid-crystal spatial modulator to control the spectrum of the Stokes pulse within a CARS scheme to optimize the vibrational contrast of CARS images. The CARS excitation spectrum is optimized for image contrast at a pre-determined wavenumber position. The optimization feedback uses an image-contrast parameter generated from the image itself as the experimentally imposed fitness parameter. This strategy allows for enhancing the image contrast by a factor of up to 2.6.