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Measurement of the laser pulse width on the microscope objective plane by modulated autocorrelation method
Author(s) -
Can F.,
Chirico G.,
Baldini G.,
Diaspro A.
Publication year - 2003
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1046/j.1365-2818.2003.01187.x
Subject(s) - autocorrelator , optics , microscope , autocorrelation , group delay dispersion , laser , interferometry , materials science , pulse width modulation , physics , full width at half maximum , mathematics , statistics , fiber optic sensor , quantum mechanics , voltage , optical fiber , dispersion shifted fiber
Summary We report on the construction details of a compact autocorrelator set‐up for the measurement of the width of infrared laser pulses at the focal plane of a microscope for two‐photon excitation fluorescence imaging. One of the novelties of the set‐up, which leads to an improved measurement accuracy, is the use of a modulation technique that is achieved by mounting one of the interferometer mirrors on a loudspeaker driven by a sinusoidal bias at low frequency. A non‐linear least‐square routine selects only that part of the fluorescence signal that is modulated at the same frequency as the loudspeaker bias. To further increase the accuracy, the laser pulse width is obtained from a series of measurements at different values of the modulation bias. The autocorrelator is a compact single bread‐board (10 × 20 cm); it is PC‐controlled both for the acquisition and the analysis of the data and can be coupled to different ports of the microscope. The increase in the pulse width measured for three different ports of the microscope is well accounted for by the group velocity dispersion and the glass thickness of the optics found along these paths.