This book addresses topics of semiconductor lasers and photonic integration. Optical communication has the higher capability of handling high-rate data processing and transmission. As efficient light emitters, the III–V materials (GaAs, InP, etc.) naturally lend themselves to integration with Si, which is already the established platform for electronic integration. Part I of this book reviews the state of the art of this technology and presents the research on a novel mode-control method to the Si/III–V hybrid lasers to enhance the modal gain, which makes for more efficient and, most importantly, shorter devices that may hold the key to the photonics–electronics integration. Part II of this book discusses circular Bragg lasers, which with an inherent large emission aperture can produce high output power with good beam quality. Their theoretical formulation is elaborated. The analytical and numerical mode-solving methods are described, followed by near- and above-threshold modal analyses and design guidelines. This book would be of interest to researchers and academics working on semiconductor lasers, integrated optics, and related areas.