Fig. 4.

Beam characteristic of the ultra-large-field-of-view two-photon scanning microscope. (a) Experimental verification of beam collimation across the full range of scan angles utilizing an interferometric shear plate. The rotation of the interference fringes at large scan angles, found from the slopes of the fringes (yellow lines) for the center and x = 4.3 mm scan positions, is consistent with a residual beam divergence of less than 1 mrad. (b) The envelope of the interferometric autocorrelation of the laser pulses evaluated through the full optical path of the microscope at the focus of the objective. The calculated fit (red) to the envelope of the experimental data (blue) is consistent with an initial pulse width of 110 fs (FWHM) that is chirped to a final width of 400 fs.