Designs of compact monolithically integrated tapered spot-size converters for efficient laser-fiber coupling

Most of the active devices have very small spot-size to enhance the physical interactions necessary for their operation, but when they are coupled to a standard single mode fiber, as much as 90% of the input power could be lost in this process. In this paper, various approaches to expand the spot-size by incorporating a monolithically integrated spot-size converter are presented. By using rigorous numerical simulations it is demonstrated that the coupling efficiency can be significantly increased along with the relaxation of the alignment tolerances.