Abstract

We review the use of Z-scan¹ for measuring nonlinear absorption (NLA) and nonlinear refraction (NLR), and we compare the information obtained with that given by other techniques, such as degenerate four- wave misting (DFWM) and third-harmonic generation (THG). For example, a normal Z-scan gives the sign of the nonlinear refractive index n₂ but does not give information regarding the response time of the nonlinearity. On the other hand, DFWM does not give the sign but does give temporal information, whereas THG can give (he sign and specifically gives information about only the ultrafast electronic response. Normally, the sensitivity of DFWM to induced phase distortion is considerably greater than that of a Z-scan. We will discuss an extension of the Z-scan that can enhance the signal by a factor of ~10, allowing induced phase distortion of less than λ/3000 to be monitored. The interpretation of data from each technique depends on the input-laser beam parameters, i,e., wavelength, mode quality, and pulse width.

© 1993 Optical Society of America