Effect of multiphoton ionization on performance of crystalline lens.

This Letter presents a model for propagation of a laser pulse in a human crystalline lens. The model contains a transverse beam diffraction effect, laser-induced optical breakdown for the creation of plasma via a multiphoton ionization process, and the gradient index (GRIN) structure. Plasma introduces the nonlinearity in the crystalline lens which affects the propagation of the beam. The multiphoton ionization process generates plasma that changes the refractive index and hence leads to the defocusing of the laser beam. The Letter also points out the relevance of the present investigation to cavitation bubble formation for restoring the elasticity of the eyes.

Enhancement of confocal microscopy images using Mueller-matrix polarimetry.

A simplified procedure based on Mueller-matrix polarimetry has recently been reported as a method of retinal image improvement in a confocal ophthalmoscope [J. M. Bueno et al., J. Opt. Soc. Am. A 24, 1337 (2007)]. Here, we have applied the technique to imaging static samples providing well-defined reflection properties. The method uses a generator of polarization states in the illumination pathway of a confocal scanning laser system. From the calculated four elements of the Mueller matrix of any sample and instrument combination, the best images defined by different metrics were constructed. For samples with specular, diffuse and mixed reflections, the best-constructed images showed an enhancement in both objective and subjective image quality compared to the original images and those obtained from frame averaging. This technique could improve microscopic imaging in many diverse fields, particularly in biomedical imaging.