Continuous alloy-composition spatial grading and superbroad wavelength-tunable nanowire lasers on a single chip

By controlling local substrate temperature in a chemical vapor deposition system, we have successfully achieved spatial composition grading covering the complete composition range of ternary alloy CdSSe nanowires on a single substrate of 1.2 cm in length. Spatial photoluminescence scan along the substrate length shows peak wavelength changes continuously from ∼500 to ∼700 nm. Furthermore, we show that under strong optical pumping, every spot along the substrate length displays lasing behavior. Thus our nanowire chip provides a spatially continuously tunable laser with a superbroad wavelength tuning range, unmatched by any other available semiconductor-based technology.