Transverse Pumping with Diode Lasers

The transverse pumping of a cylindrical laser rod such as YAG by a set of diode laser arrays equally spaced in angle around the rod has been analyzed using both geometrical and wave optics. Between the pump sources and the laser rod there may be an arbitrary number of concentric media, transparent to the pump light; and in addition modification of the diode laser radiation patterns will require other optical components. The analysis accommodates both of these complications, even when the optics in front of the diodes do not image point sources to points. It is sufficient to be able to describe the intensity and ray directions in finite apertures concentric with the rod. One result of the cylindrical geometry is the formation of caustics which have infinite intensity in the geometrical optics approximation; and it is necessary to develop a wave optics theory to predict the intensity in the neighborhood of the caustic edge of the illuminated region inside the laser rod. The wave theory first uses the geometrical optics method to calculate the amplitude and phase just inside the rod's surface, which serves then as an aperture distribution function describing the source of Huygens wavelets in the computation of a diffraction integral.