Q switching by self-focusing
A novel passive technique for obtaining short-laser-pulse emission is presented. A cell with a high-second-order refractive-index liquid is included in an unstable laser cavity. The external self-focusing introduced by the cell at higher optical intensities reduces the diffraction losses, producing modulation of the gain and Q switching of the cavity. Compared with saturable absorbers, this method provides better mode quality, avoids filamentary emission, and is not restricted in wavelength. Experimental results are presented that are in good agreement with the numerical model developed.