Vol. 31, Issue 2, pp. 373-376 (2001)

Abstract

Laser diode pumping in commonly applied in all solid state laser devices. In the case of an upconversion laser, i.e., when infrared-to-visible upconversion takes place in a rare-earth doped optical fiber, laser diode pumping is of special interest. Excitation of a single mode optical fiber, typically of core diameter of about 2 μm, requires that the emitting area of the diode must be limited to 1 μm *3 μm, otherwise its emission cannot be focused to a spot of a few micrometers in size. As we have shown, short focal length lenses of high (NA approximately=0.4) ensure the best results. Numerical aperture (NA) matching is of less importance.