Abstract

To understand the propagation of sub-nanosecond laser pulses operating in the visible and near infrared in tissues such as ocular components, water is used as a baseline model both theoretically and experimentally to determine the onset of optical nonlinearities such as nonlinear absorption. Preliminary data obtained from parallel experiments by using the z-scan technique in the picosecond time domain at 532 nm indicates that the nonlinear refractive indices for water and ocular media are quite close in magnitude and have the same sign. Thus, water is an excellent model for investigating subnanosecond propagation phenomena as it relates to nonlinear absorption in ocular media. We use a simplistic model reminiscent of Beer's law to describe how nonlinear absorption is mediated by the propagating field intensity. Coupled to the model, we measure linear absorption data as a function of intensity in ultrahigh purity water by using a Michelson type apparatus¹ and continuous wave sources in the visible spectral region. Absorption data is tabulated, and its effect on sub-nanosecond laser pulse propagation in ocular media is discussed.

© 1992 Optical Society of America