Low-loss adhesive-free fiber connections for high-power laser transmission

We report on a technique for obtaining adhesive-free optical bonds between optical fibers and a wide range of optical elements, including other optical fibers. This technique overcomes problems associated with epoxies or inorganic adhesives at the bond interface. It consists of optically contacting a precision polished flat fiber-ferrule assembly against a precision polished mating surface. The optical fibers and ferrule both are of the same or similar material, e.g. fused silica, and the optical fiber inside the ferrule has been stripped of its organic polymer coating. The optical bond is then heat treated to produce a strong permanent bond with negligible loss at the interface. Applications include the attachment of a fused silica optical fiber/ferrule assembly to an optical element of fused silica with negligible Fresnel reflection loss. This type of connection is capable of transmitting high-power laser radiation to a site for materials processing without laser damage at the interface. Another important area of use for optically bonded interfaces is the delivery of high-power diode laser pump radiation to a clad laser fiber.