In accordance with one embodiment of the present invention, a method of characterizing a lens is provided. According to the method, an optical source such as a laser is configured to generate a collimated beam that is focused along an optical axis at a distance f.sub.ext. A test lens is placed along the optical axis, wherein the test lens is characterized by an effective focal length f.sub.i that is substantially independent of incident irradiance. An output beam generated from the focused optical source and the test lens defines an output intensity profile at an observation plane located a distance Z.sub.0 from the focal point of the optical source. The on-axis intensity I of the output intensity profile along the optical axis at the observation plane is monitored as the placement of the test lens along the optical axis is varied. A z-scan signature of the test lens is generated from the monitored intensity I. The z-scan signature is a plot of intensity as a function of .DELTA.z, where .DELTA.z represents a distance between a position of the test lens and the focal point f.sub.0 along the optical axis. The effective focal length f.sub.i of the test lens is characterized by determining the slope m.sub.0 of the z-scan signature at .DELTA.z=0. Additional embodiments are disclosed and claimed.