Hybrid laser-to-fiber coupler with a cylindrical lens.

Several laser-to-fiber coupling schemes have been compared with regard to coupling efficiency. A coupling scheme with a cylindrical lens is simple and effective for enhancing coupling efficiency. As a mounting and aligning structure for the laser-to-fiber coupling with a cylindrical lens, a hybrid structure has been proposed using a copper mount on which two vee grooves are produced for aligning all optical elements without adjustment. Even though the mounting structures have been produced by machining, the average coupling efficiency of about 50% has been achieved when using a multimode optical fiber with a half acceptance angle of 3-4 degrees . The couplers have been successfully mounted in hermetically sealed laser packages, indicating feasibility and usefulness for practical applications.