This integrated system proposal focuses on novel multi-channel wavelength-division-multiplexed (WDM) semiconductor lasers based on a monolithically integrated compact diffraction grating technology for wavelength multiplexing that is substantially smaller. In this proposal, we will use the grating to realize an integrated photonic chip that has many individually addressable lasing wavelengths all multiplexed into a single output waveguide. Such semiconductor laser subsystems, called the "WDM lasers", are important key devices for dense WDM (DWDM) networks. Current DWDM multichannel laser transmitters are discrete-device based with array-waveguide-grating (AWG) module joined to multiple modules of distributed feedback (DFB) lasers, resulting in a subsystem size ~16,000mm2. We will realize WDM lasers on a chip no larger than 2-4mm2 with 4-8 individually addressable lasing wavelengths efficiently multiplexed into a single fiber output. The proposed works will lead to significant advancements in next-generation communication and WDM photonic device integration technology. The realization of next-generation integrated WDM photonic devices will have substantial impacts on U.S.'s competitiveness in photonic technology areas. The proposed works will contribute significantly to these broad impacts. The PI is a member of the NSF Materials Research and Engineering Center (MRSEC) at Northwestern University and has involved high-school teachers for summer research. The PI is also a member of Northwestern Center for Photonic Communication and Computing (CPCC). Both MRSEC and CPCC provide venues for collaboration, coordination, dissemination, and promotion of research and teaching activities that often involve the general publics, minority students, and high school students.