Improvement of axial response in three-dimensional light focusing by use of dynamic phase compensation

Abstract

The axial response of a high numerical aperture (NA) optical system is known to be very sensitive to any mismatch in refractive index between that of a specimen and that of an immersion medium. Light focused deeply into the specimen is usually strongly degraded by spherical aberration resulting from the refractive index mismatch. Even an extremely small amount of spherical aberration has been shown to be enough to produce a substantial degradation of the point spread function (PSF) far more in the depth than in the lateral direction. Various approaches to correcting these aberrations have been proposed in the literature. However, most approaches only consider first-order aberration correction and/or the proposed methods only work for a given and fixed focusing depth[1-3]. Here we will consider the possibility for dynamically compensating for all orders of spherical aberration resulting from refractive index mismatch by use of a phase-only spatial light modulator (SLM).