Multicolour wavelength-tunable lasing from a single bandgap-graded alloy nanoribbon

Tunable lasing from 578 nm to 640 nm is observed from a single CdSSe bandgap-graded alloy nanoribbon, by selecting the excited spot at room temperature. Though reabsorption is a serious problem to achieve lasing at short wavelength, multiple scatters on the nanoribbon form localized cavities, and thus realize lasing at different wavelengths. By increasing the excitation area, we also observe multicolour lasing from the same nanoribbon simultaneously.