In this work, efforts were made for the investigation on broadband semiconductor laser. First, a broadband dual-wavelength semiconductor laser with single gain medium will be demonstrated. A record wavelength separation up to 203nm can be achieved with this laser system. Second, a new phenomenon called mode anti-competition will be discussed. This phenomenon is opposite to traditional mode competition, and can only be observed at wavelength separation above 60nm. Finally, simultaneous generation of eight wavelengths with 20nm channel spacing from single semiconductor laser will be demonstrated. The applications of this broadband laser system will also be discussed.