Bloch Surface Wave-Coupled Emission from Quantum Dots by Ensemble and Single Molecule Spectroscopy.

We report the spectral properties and spatial distribution of quantum dot (QD575 ) emission on a one-dimensional photonic crystal (1DPC). Our 1DPC substrate consists of multiple layers of dielectrics with a photonic band gap (PBG) near the QD575 emission maximum. The 1DPC was designed to display a surface-trapped electromagnetic state known as a Bloch surface wave (BSW) at the 1DPC-air (sample) interface. Ensemble angle-dependent emission intensities revealed a sharp angular emission peak near 41° from the normal which is consistent with the BSW resonance at 575 nm. We further examined the emission from single QDs on the 1DPC. A notable increase in fluorescence intensity from QD575 particles was observed on BSW substrate compared to the glass substrate from the scanning confocal fluorescence images and from the intensity-time trajectories of single QD575 particles. The intensity-decays showed substantially faster decay (4-fold decrease in emission lifetime) from the single QD575 particles on 1DPC substrate (∼4.8 nsec) as compared to the glass substrate (∼18 nsec). We observed the spectral characteristics of the individual QD575 particles on 1DPC and glass substrates, by recording the single particle emission spectra through the 1DPC. The emission spectra of the single QD575 particles are similar (with emission maxima around 575 nm) on both substrates except a substantial increase in intensity (over 10-fold) on the BSW substrate. Our results demonstrate that quantum dots can interact with Bloch Surface Waves (BSW) on a 1DPC. To the best of our knowledge, this is the first report on the single particle fluorescence studies on 1DPC substrate. The 10-fold increase in intensity in combination with 4-fold reduction in emission lifetime suggest 1DPCs with BSW modes have potential use in sensing and single molecule spectroscopy.