Martinez, O. E., authorMarconi, Mario Carlo, authorDiodati, F. P., authorOptical Society of America, publisher2007-01-032007-01-031986Marconi, M. C., O. E. Martinez, and F. P. Diodati, Second Threshold Condition in the Case of Q Switching by Self-Focusing, Journal of the Optical Society of America. B, Optical Physics 3, no. 12 (December 1986): 1630-1636.http://hdl.handle.net/10217/67854In a recent paper [Opt. Lett. 10, 402 (1985)] we presented a novel passive technique for obtaining giant laser-pulse emission. In this paper we present a more sophisticated model based on Kirchhoff-Fresnel diffraction theory that confirms the aberrationless Gaussian model used before. Also, a simple criterion for short-pulse generation in the Q switch by the self-focusing technique is derived. A set of equations is obtained that permits the evaluation of the critical parameters that govern the laser dynamics. The second threshold condition is derived, and some typical examples are pointed out.born digitalarticleseng©1986 Optical Society of America.Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Text