Abstract
In this work, the DC two-photon absorption signal offset (${{\rm DC}_{\rm TPA}}$) and the amplitude of the autocorrelation (${{\rm A}_{\rm AC}}$) are measured simultaneously around the focal point of an apochromatic microscope objective using the z-scan autocorrelation technique. The ${{\rm A}_{\rm AC}}$ is obtained from the nonlinear sensor response given by the two-photon-absorption, generated in a GaAsP photodiode, for femtosecond laser pulses. We verify that the change in the ${{\rm DC}_{\rm TPA}}$ signal along $z$ is coincident with the amplitude of the intensity autocorrelation, and that the highest amplitude of the AC is reached at the same position as the highest amplitude of the ${{\rm DC}_{\rm TPA}}$ signal. The ${{\rm DC}_{\rm TPA}}$ signal is typically used as a reference for the alignment in a collinear intensity autocorrelator, and we show that it can also be used as a practical procedure to estimate the depth of focus. The ${{\rm DC}_{\rm TPA}}$ signal measurement allows us to locate the optimum spatial-temporal coupling given by the highest amplitude of the intensity autocorrelation. Additionally, we find a variation in the pulse duration within the same region due to the radially varying group delay dispersion.
© 2020 Optical Society of America
Full Article | PDF ArticleMore Like This
P. Castro-Marín, G. Castro-Olvera, J. Garduño-Mejía, M. Rosete-Aguilar, N. C. Bruce, D. T. Reid, and O. G. Rodríguez-Herrera
Opt. Express 25(13) 14473-14482 (2017)
Patrick Langlois and Erich P. Ippen
Opt. Lett. 24(24) 1868-1870 (1999)
José Agustín Moreno-Larios, Martha Rosete-Aguilar, Oscar G. Rodríguez-Herrera, and Jesús Garduño-Mejía
Appl. Opt. 59(24) 7247-7257 (2020)