Efficient coupling of light from semiconductor lasers to single-mode fibers is desirable for applications such as fiber optic communications and large scale photonic integrated circuits. A novel architecture which has been theoretically analyzed is experimentally demonstrated in this work. Such a device efficiently couples light from a III-V semiconductor laser waveguide to a fiber-like polymer waveguide. The analysis, design, fabrication and testing of a polymer/semiconductor leaky-mode grating-assisted directional coupler (LM-GADC) are the focus of this work. The LM-GADC device consists of a coupling grating, a polymer sub-waveguide and a III-V semiconductor sub-waveguide. The devices can be monolithically integrated with semiconductor lasers with an emission wavelength lambda ≈ 1310 nm; modifications of the design may allow for development at other wavelengths. The structure of polymer/semiconductor LM-GADC is analyzed using Floquet-Bloch theory, an eigenvalue technique which more accurately solves the radiation losses due to the improper leaky modes and predicts the coupled power and coupling length. A sensitivity analysis is performed on important parameters of the device to optimize the structure configuration. The maximum theoretical power transfer from the semiconductor sub-waveguide to the polymer sub-waveguide is up to 30% for a simple LM-GADC without the incorporation of multilayer reflective stacks. Challenges in the fabrication of second order gratings at various lengths and cleaving of polymer waveguide facet are overcome by the development of two relatively complicated process procedures. Because of the difficulty of quantitating the input and output power of the device, the coupling efficiency and the transmission spectrum are not measured. Instead, light coupling from the semiconductor sub-waveguide to the polymer sub-waveguide as a function of excitation wavelength is recorded. Experimentally measured ratios of the peak intensities in the two sub-waveguides at different specific wavelengths to the theoretically predicted ratios are compared. The results show that the experimental data are in agreement with the simulation analyses.