Abstract: An arrangement of optical resonators which are composed of elongated optical waveguides comprising reflectors arranged at their end faces, one group of the waveguides being coupling resonators and a second group of the waveguides being useful resonators which are arranged in a substrate with the useful resonators being adjacent one surface thereof. A laser active material is provided adjacent the one surface of the substrate and can be either a semiconductor laser material or can be a light pump laser material. At least one of the waveguides of the useful resonators being composed of optically passive material, which has good wave-conducting properties, and being positioned adjacent to the laser active material so that a wave field excited in the waveguide can be intensified by the laser active material.

Abstract: For heating synthetic yarns and fibers an elongated vessel filled with saturated steam is provided through which the yarn is continuously drawn. The steam condensates on the yarn and transfers its condensation heat to the yarn. For sealing the vessel (3) at the inlet (2) and the outlet (4), several apertures (6-9, 13-16) are provided in a pair of tubes (5,12) surrounding the traveling path of the yarn (1). The space between the first aperture and the opening adjacent the steam vessel (3) is connected to a blocking liquid supply pipe (30) and the space between the last aperture (9,16) and the inlet hole (10) and the outlet hole (17), respectively, for the yarn is connected to a blocking liquid return pipe (31). The blocking liquid supply pipe is kept under a pressure which is somewhat higher than the pressure within the steam vessel (3).