Femtosecond optical ranging in biological systems

Abstract

Optical ranging using femtosecond laser pulses and nonlinear-optical cross correlation is demonstrated for the investigation of the microstructure of biological systems. By using pulses of 65-fsec duration generated by a colliding-pulse mode-locked ring dye laser, a spatial resolution of less than 15 μm is achieved with a detection sensitivity to remitted signals as small as 10−7 of the incident pulse energy. This technique is applied to measure the cornea in rabbit eyes in vivo as well as to investigate the epidermal structure of human skin in vitro.