Lateral composition-graded semiconductor nanoribbons for multi-color nanolasers

Low-dimensional semiconductor nanostructures have attracted much interest for applications in integrated photonic and optoelectronic devices. Band gap engineering within single semiconductor nanoribbons helps to manipulate photon behavior in two different cavities (in the width and length directions) and realize new photonic phenomena and applications. In this work, lateral composition-graded semiconductor nanoribbons were grown for the first time through an improved source-moving vapor phase route. Along the width of the nanoribbon, the material can be gradually tuned from pure CdS to a highly Se-doped CdSSe alloy with a corresponding band gap modulation from 2.42 to 1.94 eV. The achieved alloy ribbons are overall high-quality crystals, and the position-dependent band-edge photoluminescence (PL) emission had a peak wavelength continuously tuned from ~515 to ~640 nm. These ribbons can realize multi-color lasing with three groups of lasing modes centered at 519, 557, and 623 nm. It was confirmed that the red lasing was from optical resonance along the length direction, while the green and yellow lasing was from optical resonance along the width direction. These novel nanoribbon structures may be applied to many integrated photonic and optoelectronic devices.