Saturable absorption assisted nonlinear structured illumination microscopy.

We propose a novel, to the best of our knowledge, super-resolution technique, namely saturable absorption assisted nonlinear structured illumination microscopy (SAN-SIM), by exploring the saturable absorption property of a material. In the proposed technique, the incident sinusoidal excitation is converted into a nonlinear illumination by propagating through a saturable absorbing material. The effective nonlinear illumination possesses higher harmonics which multiply fold high frequency components within the passband and hence offers more than two-fold resolution improvement over the diffraction limit. The theoretical background of the technique is presented, supported by the numerical results. The simulation is performed for both symmetric as well as random samples where the raw moiré frames are processed through a blind reconstruction approach developed for the nonlinear SIM. The results demonstrate the super-resolution capability of the proposed technique.