We report a single-beam, differential z-scan technique with improved sensitivity for the determination of nonlinear absorption and refraction of materials. A sample is scanned in the direction of beam propagation as usual, but, in addition, its longitudinal position is dithered, producing a detector signal proportional to the spatial derivative of only the nonlinear transmission and therefore giving a background-free signal; the nonlinear transmission for any spatial position of the sample can be recovered by simple integration.
For both open and closed aperture scans in GaP, we find an improvement in the signal-to-noise ratio of
© 2007 Optical Society of America
Original Manuscript: October 3, 2006
Revised Manuscript: November 24, 2006
Manuscript Accepted: November 30, 2006
Published: March 20, 2007
Jean-Michel Ménard, Markus Betz, Iliya Sigal, and Henry M. van Driel, "Single-beam differential z-scan technique," Appl. Opt. 46, 2119-2122 (2007)