A new method for computing eigenmodes of a laser resonator by the use of fi-nite element analysis (FEA) is presented. For this purpose, the scalar wave equation [? + <i>k</i> <sup>2</sup>]<i>?</i>(<i>x</i>, <i>y</i>, <i>z</i>) = 0 is transformed into a solvable 3D eigenvalue problem by separating out the propagation factor exp(-ikz) from the phasor amplitude <i>?</i>(<i>x</i>, <i>y</i>, <i>z</i>) of the time-harmonic electrical field. For cavities with parabolic optical elements the new approach has successfully been verified by the use of the gaussian mode algorithm. For a DPSSL with a thermally lensing crystal inside the cavity the expected deviation between gaussian approximation and numerical solution could be demonstrated clearly.

© 2004 Optical Society of America

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