Broad spectral response in composition-graded CdSSe single nanowires via waveguiding excitation

We report broad spectral response in composition-graded CdSSe single nanowires (NWs) via waveguiding excitation. The excitation light is coupled to CdSSe single nanowires via silica fiber tapers. The guided photons in the nanowire with energies ranging from 1.74 to 2.44 eV can be efficiently captured at different sites along the NW length. Compared to single-composition nanowires, the composition-graded CdSSe nanowires exhibit much broader spectral response range, while retaining the detection limit down to sub-pW level. Utilizing the photoconductive quenching effect, the spectral range can be further extended beyond 1.5 mu m with detection limit down to sub-nW level at room temperature. (C) 2011 American Institute of Physics. [doi:10.1063/1.3657523]