Abstract: An assembly for focusing and coupling radiation produced by a semiconductor laser into an optical fiber, in particular a multimode optical fiber, including a radiation-focusing element in the form of cylinder lens disposed in the area between the radiating surface of the semiconductor laser and light entrance side of the optical fiber, the length of the cylinder lens being at least equal to a width of a beam exit window defining the radiation surface of the semiconductor laser, and the diameter of the cylinder lens being substantially on the order of magnitude of the core diameter of the optical fiber. The cylinder lens is in the form of glass fiber lens directly glued onto, fused with, or melted onto the light entrance side of the optical fiber which extends substantially at right angles to the orientation of the cylinder lens.

Abstract: A diode-pumped solid state laser for single-mode operation contains a resonator with an input mirror and an output mirror between which an active laser medium, a polarizer and a birefringent crystal are disposed. The crystal is disposed with its optical axes in such a way that the latter form an angle of 45.degree. to the polarizing direction produced by the polarizer. The losses for the ordinary and extraordinary rays are adjusted to be substantially equal. A temperature control means is used to keep the temperature of the birefringent crystal at a constant value so that the refractive indices and the length of the crystal do not change.