Abstract: A high-output, single fundamental transverse mode solid state laser is disclosed which uses a semiconductor laser array as an excitation light source. The solid state laser comprises: a laser element which includes a core containing an element added as a laser medium, a cladding containing no such laser medium element, and reflecting mirrors coated over the cladding surface for repeatedly reflecting incident excitation light so that it may repeatedly pass through the core; an excitation light source formed by semi-conductor laser or light emitting diode array; means for guiding the excitation light from the excitation light source to one side of the laser element for incidence thereto; and a resonator for the oscillation of the solid state laser.

Abstract: A method and an apparatus for manufacturing a fluoride glass fiber preform are disclosed which preclude the step of pouring a glass melt into a mold from a crucible, and hence permit the fabrication of a long, homogeneous fluoride glass fiber preform free from foreign substances and air bubbles leading to scattering and which also allow ease in the fabrication of a preform having an elliptic core portion for drawing a polarized wave retaining fiber.

Abstract: A fusion splicing method for optical fibers in which optical fibers are fusion spliced in an inert gas atmosphere after water adsorbed on their surfaces is removed by decomposition in a plasma of an inert gas containing a halogen.

Abstract: A method and apparatus is disclosed which ensures highly accurate control of the core-cladding diameter, enabling the fabrication of a preform for the single mode fiber. Moreover, glass refining steps for dehydration, the removal of compound ions, the reduction of the absorption loss by transition metals, etc. and preform manufacturing steps are combined into a series of steps, and the entire manufacturing process can be mechanized and automatically controlled; therefore, the yield rate of product is high and the industrial-scale productivity is also excellent.

Abstract: In a fluoride glass optical fiber with extremely small transmission loss for infrared light having a core layer and a clad layer each consisting mainly of ZrF.sub.4 - BaF.sub.2 - LaF.sub.3 - AlF.sub.3, NaF and H.sub.f F.sub.4 are used as additives to obtain a desired refractive index difference between the core layer and the clad layer. The mixing ratio of the NaF to the H.sub.f F.sub.4 satisfies the realtions;.vertline.0.25 .DELTA.H.sub.f F.sub.4 -3.DELTA.NaF.vertline..ltoreq.5,where .DELTA.NaF is the difference between the amount (mol %) of the N.sub.a F to be added to the core layer and that to be added to the clad layer, and .DELTA.H.sub.f F.sub.4 to be added to the core layer and that to be added to the clad layer.

Abstract: A fluoride glass for infrared optical transmission fiber is purified for dehydration and deoxidation to reduce transmission loss by reacting melted fluoride glass with NF.sub.3 gas at temperature between 500.degree. C. and 800.degree. C. No scattering loss is increased by the present purification as decomposed product in the reaction does not precipitate.