Despite their broad applications, up to date, diode pumped solid state green lasers are almost exclusively dominate the market due to the lack of low defect or defect-free semiconductor materials with high efficiency at green wavelength (480-550nm). We propose to develop compact, high efficiency, and high brightness III-nitride based green lasers. In phase I, we will focus on design, epitaxial growth and prototype fabrication of green lasers. The high efficiency, high brightness green lasers will be realized in phase II through optimization of materials growth and device processing. Two approaches will be considered, including thin-film structures and nanowire structures grown by plasma assisted molecular beam epitaxy (MBE).