Variational Analysis of z Scan of Thick Medium with an Elliptic Gaussian Beam

By variational approach, we analyze the characteristics of beam propagation through a cubic optical nonlinear medium using a laser beam that has a transverse elliptic Gaussian profile. The analytic solution to the normalized transmittance at the center of the far field as a function of medium position and the beam characteristics is obtained and compared with the numerical simulation, which is realized by a combination of algorithms. We also analyze the peak-valley transmittance difference as a function of medium length, ellipticity, and astigmatism. The relationship between peak-valley normalized transmittance difference of the z -scan trace and aperture size or the slit width are obtained. Meanwhile, the comparison of z -scan characteristics with an elliptic Gaussian beam with those using a circular symmetric Gaussian beam is made.