Rainbow on a Chip: Experimental Observation of the Trapped Rainbow Effect Using Tapered Hollow Bragg Waveguides

Experimental observation of the ‘trapped rainbow’ in the visible is demonstrated using tapered hollow Bragg waveguides. These waveguides spatially disperse an input spectrum into its various frequency components and vertical out of plane radiation was observed at wavelength dependant positions along the entire length of the waveguide. The experimental observation is corroborated by a brief theoretical analysis and simulation. These devices form the foundation for future work involving integration into a micro-spectrometer for eventual lab-on-chip use.