Self-Absorption Effect in the Spatial Resolved Spectra of CdS Nano-Ribbon Optical Waveguide Observed by Near-Field Spectroscopy

Abstract

Scanning near-field optical microscopy (SNOM) and spectroscopy were used to study the light emission characteristics of CdS nano-ribbon optical waveguide. A continuous red-shift of photoluminescence (PL) spectra of such nano-ribbons with the increase of the light propagation distance was observed. Near-field optical images indicate that CdS nano-ribbon can work well as an optical waveguide. Quantitative calculation was made to demonstrate the PL attenuation with long propagation distance (typically several hundreds μm). The red shift is attributed to self-absorption, which means re-absorption and re-emission among energy-valleys with different energies of conduction bands. Our results draw attention to the spectral characteristics of nano-ribbon optical waveguides, which are as important as intensity to the stability and veracity of information transmission.