| The coupling of laser with fiber has been used in many fields, such as industry, medical treatment, communications. At the present time, the coupling methods are mainly direct-coupling and lens coupling. For the existence of a damage threshold in fiber end face and interior, it is very difficult to use the above ways to realize the coupling of high-power, high-energy and narrow pulse laser with optical fiber.In this paper, on the basis of analyzing the mechanism of damage of optical fiber, a new method has been presented to reduce laser power density and energy density in optical fiber end face and interior and a hollow cone shaped laser-fiber coupler has been designed. When cylindrical Gauss beam incident into the hollow cone coupler, it will form a light spot which the energy density becomes quasi-average distribution. So the energy density of laser on the fiber end face has been reduced effectively. By using this coupler, the coupling of a high-power(lOMW), energy(12MJ), narrow pulse (12ns) and electro-optical Q-switched Nd:YAG laser with the multimode optical fiber (diameter is 600μm) has been realized and the coupling efficiency is 72%. |
